Mountain Weather

Good Dump Producer

2012-02-29T12:50:00.010-08:00

Wednesday, Feb. 29th, 2012...............A nice combination of features on the weather maps today, all lining up to become a good dump-producer for Jackson Hole & the Tetons today. And then Swinging south over Utah and Colorado tonight & Thursday.

Low pressure center at the surface over the Northwestern US today, this will be moving across the Rockies in two pieces, with one piece passing by to the North of Jackson Hole, in Montana ( a really good position for Northwest Wyoming's mountains). The second piece of that Low pressure center will be dropping south over the Utah/Colorado border area.

There is also a cold front that will be plowing through this afternoon, adding some extra boost to the weather system, and intensifying the snowfall over the Tetons and eventually over parts of Utah & Colorado's mountains.

All of that stuff east moves into the Plains on Friday.

Surface Map below left, Jet Stream Map below right..........

Upper Level Trof of Low pressure is also in a good position, with a nose of the jet stream also moving overhead today, along with a good diverging West to SW flow out ahead of the Trof. To top it off with a little extra sauce, there is also a strong Northwest flow on the backside of this Trof, which is providing an ample supply of cold air aloft (along with Pacific moisture) to keep things unstable.

That's the technical jibberish.... But it all translates into a big dump to skiers.

You can check out the newest 3-Day Surface Maps and Jet Stream Forecast Maps on the USA Forecasts Page on www.mountainweather.com

I just added a new look and content to that page today. Check it all out. And while you are there, have a look at the Satellite & Radar page too, pretty good looking right now!

Graphics from NWS & UCAR.
Posted by meteorologist Jim Woodmencey

Snowfall Playing Catch-up and Gaining!

2012-02-23T08:15:00.012-08:00

We have had a lot to make up for with snowfall this winter, with a slow start to the season. Snow storms have been fewer and farther between than last winter, but this past week's snowfall has almost caught us up to where we should be this time of year.

It has generally been a feast or famine cycle for powder this season, with three good stormy periods that stick out: one around New Year's, one the third week of January, and now this one during the second to third weeks in February.

We are just past the mid-point of the Winter Season now, and maybe we can relax a little as settled snow depths are now very close to normal for this time of year in the mountains, thanks to the snow of this past week. As as you can see in the table below, we're not grossly behind where we were last year at this time, for settled snow depths.

Settled Snow Depth Comparison (Inches) on February 23^rd Jackson Hole Mountain Resort
Weather Station	This year Feb. 23, 2012	Average Feb. 23rd	Last Year Feb. 23, 2011
Rendezvous Bowl (9,580-ft.)	89	90	108
Raymer Plot (9,360-ft.)	92	83	101
Mid-Mountain (8.180-ft.)	78	82	90
Base (6,510-ft.)	34	35	36
Data from Bridger-Teton National Forest Avalanche Center

February 14 to 22 Snow & Wind
Between Valentine's Day and Washington's Birthday there has been about 4 feet of new snow at the higher elevations. Rendezvous Bowl had 44 inches and the Raymer Plot had 48 inches.

Distribution was a little askew when comparing these two stations at roughly the same elevation, during the first half of this past week (Feb. 14 to 20) Rendezvous Bowl had 20 inches of snow and the Raymer Plot reported 15 inches.

During the second half of this past week (Feb 21 to 23) Rendezvous Bowl showed a total of 22 inches of new snow and the Raymer Plot recorded 33 inches of snow. Not to shabby for February, which is usually the driest month of the winter, on average.

It was also VERY windy during this period, with 30 to 39 mph sustained winds in the valley and gust to 55 mph. In the mountains averages were sometimes between 40 and 50 mph with gusts near 80 mph in the Teton Range. The jet stream was right over head Wednesday evening when winds were at their peak, and estimated to be between 130 and 150 mph at 30,000-ft.

Total Season Snowfall
We are still behind on our season total snowfall numbers and nowhere near where we were last winter. See comparison table below.

Total Season SnowfallComparison (Inches) as of February 23rd Jackson Hole Mountain Resort
Weather Station	This year Feb. 23, 2012	Average on Feb. 23rd	Last Year Feb. 23, 2011
Rendezvous Bowl (9,580-ft.)	252	302	359
Raymer Plot (9,360-ft.)	264	350	390
Mid-Mountain (8.180-ft.)	231	276	323
Base (6,510-ft.)	96	131	138
Data from Bridger-Teton National Forest Avalanche Center

Snotel Reports also indicate that the Snow Water Equivalent (SWE) is now at 92% of average. So it is looking like the middle part of winter is proving to be the fattest, as far as snowfall goes.

The best news for Jackson Hole skier's is, that we are still looking fatter than much of the rest of the Western United States. (See National and regional snowdepth maps below, as of Feb. 23, 2012.

Snow Analysis maps can be viewed on the Skier's Page on www.mountainweather.com

Posted by Meteorologist Jim Woodmencey
February 23, 2012

Northwesterly Flow or a "Dirty Ridge"

2012-02-20T07:32:00.000-08:00

Surprisingly, we have managed to pick up roughly 20 inches of new snow in the Teton Mountains since Valentine's Day (Totals for Feb. 13 thru 19) with weak Low pressure systems wandering around the Western U.S.

While we have spent the better part of the last 3 weeks without a significant jet stream flow over the Western U.S. it finally looks like that will be changing here this week as we come under a stronger Northwesterly flow beginning tonight and Tuesday (Feb. 21st)

That jet stream will be positioned just to the north of Jackson Hole, so we will start out initially with warmer air Tues. into Wed. Then, that jet drops further south Wed. night & Thurs. bringing colder air with it.

Jet Stream Map for Wednesday Feb. 22nd

A Ridge of High pressure will be positioned off the West Coast and moisture associated with Low pressure systems in the Gulf of Alaska and further out in the Pacific will be directed up and over the top of that Ridge and straight over us in a consistent NW flow aloft.

This is not a “storm” per say, but rather a very moist and consistent Northwesterly flow, which is usually a very favorable flow to have for producing decent snowfall in the Tetons. You might also call this a “Dirty Ridge” situation, where moisture rides over the top (northern part) of a Ridge of High pressure that is usually located along or just off the West Coast. Snowfall will follow the trail of moisture, and generally will be in the vicinity of the jet stream flow, as well.

Maps below of Forecasted Snowfall for Western U.S.
And zoomed-in map of Idaho-Montana-Wyoming
for Monday Feb. 20 thru Wednesday Feb. 22

Looks like the best snowfall for us will come Tuesday afternoon thru Wednesday afternoon, with very strong winds developing, especially in the mountains. This model above shows something in excess of 25 inches of snow at the higher elevations in the Tetons thru Wednesday evening. More conservatively, I think you can count on snow accumulations in the mountains of between 1 and 2 feet.

Snow tapers off for Thursday, then we see a Low pressure system drop south out of B.C. at the end of the week, which will bring more snow to NW Wyoming Friday and over the weekend.

Groundhog's Day

2012-02-02T03:39:00.000-08:00

It's Groundhog’s Day! Perhaps the most "celebrated" weather day of the year....but it really has less to do about the groundhog and more to do about the fact that February 2nd is the midway point of the Winter Season.

According to folklore, if the day is sunny and the groundhog (otherwise known as a woodchuck or marmot) sees his shadow, then we will have six more weeks of winter. If the day is cloudy and the groundhog doesn’t see his shadow, then spring will come early.

The thinking here is, that if it is a sunny day in early February, then something is amiss with the weather and the groundhog will dive back in his hole, expecting that winter weather will likely return in March. If it is cloudy, and he can't see his shadow, then the weather situation is "normal" and spring should arrive early. At least that is one interpretation of the myth surrounding the groundhog.

Truth is, groundhog's rarely come out of hibernation and show their faces before the end of March. With the exception of a few domestically held groundhog's & marmots like Punxsutawney Phil & Lander Lil.

The real reason for celebration is that Groundhog’s Day does mark the midway point of the Winter Season. Winter is 12 weeks long, and February 2nd is exactly the midway point between December 21st (the solstice) and March 21st (the equinox). Regardless of what the groundhog says, we will always have 6 more weeks of winter between today and March 21st, according to the calendar at least.

Spring may come early to some parts of the country, and we may see some “spring-like” weather here in Jackson Hole before the third week in March. But rarely is our winter weather over with before March 21st.

Posted by meteorologist Jim Woodmencey
February 2, 2012

This January Storm Cycle

2012-01-23T09:17:00.000-08:00

A steady and sometimes powerful Westerly flow brought the bulk of the snowfall between Wednesday January 18^th and Saturday January 21^st , 2012. Storm totals for the entire 7-day period from last Monday morning, January 16^th thru this Monday January 23^rd 2012 were pretty impressive, with around two feet of snow falling in the valley and over 4 feet of snow in the mountains around Jackson Hole. That snow contained over 2 inches of water at lower elevations and more than 4 inches of water at higher elevations.

Getting a big dump of snow like that is not without its problems though, and hats off to the WYDOT crew for being on top of it and keeping things safe on Teton Pass during a busy avalanche cycle. (See some photos below from Jamie Yount, Avalanche Forecaster for WYDOT). And good job also to the local area ski patrols for doing the same, not an easy task when you are dealing with that much snow and that much wind in a relatively short amount of time.
As much as we all were yearning (and maybe a little crazy!) for fresh powder, patience is a valuable virtue when the mountains are rocking and rolling like they were.

Photos from Left to Right...Glory Bowl Crown. Bottom of Glory at Road. Beaver Slide debris on West side of Teton Pass. (All Courtesy of Jamie Yount, WYDOT).

Snowfall Numbers

Basically our snowpack doubled in less than a week, going from a settled snowdepth in the valley of around 16 inches last Monday to 37 inches this Monday. Mountains did the same, growing from around 40 inches to 80 inches tall.

Snowfall numbers and comparisons below for the Rendezvous Bowl Study Plot at the Jackson Hole Mountain Resort.

Snowfall Stats for Rendezvous Bowl ( 9580-ft.) JHMR
Total Storm Snow Jan. 17 to 22	Total Storm Water Jan. 17 to 22	Settled Snow Depth on Jan. 16th	Settled Snow Depth on Jan. 22nd	Average Snow Depth on Jan 22nd
55 inches	4.16 inches	43 inches	80 inches	73 inches
Data from Bridger-Teton National Forest

Numbers from the Teton Pass Study Plot that WYDOT uses, on the West side of the Pass had 48 inches of snow for the storm through Sunday morning (but some of that settled well before they could go measure it) and a whopping 5.40 inches of water!

Snow in Other Areas

Best swath of snow with this moist Westerly flow was from the Cascades of Washington, across the mountains of Idaho and into Western Wyoming. Big Winner was Mt. Baker in Northwest Washington where they reported 95 inches of snow in the last 10 days and a settled snow depth of 166 inches, looking like the deepest in the lower 48 U.S. right now.
Brundage Mountain near McCall, Idaho reported 40 inches of snow this past week and they now have a settled snow depth of 72 inches.
Significant snow also fell in Utah and Colorado’s mountains, but not nearly as much as the aforementioned areas, but enough to cause avalanche problems down that way also. Since everywhere snow fell, it fell on a weak existing snowpack.
Oddly, there were parts of central Idaho and Southwest Montana’s mountains that got significantly less snow. There were some mountain areas that got short-changed by this moist Westerly flow (For example: Sun Valley got way less snow than Brundage Mountain & Bridger Bowl got way less snow than Montana SnowBowl). That was probably due to some downsloping effects as moisture was lifted over mountain ranges to the west and then created a “dry-hole” to the leeward, unable to lift over the next adjacent range in time to dump out more snow. Best I can do to explain that for now without further investigation.
To be honest, I hardly gave these places a thought until after the fact, mainly because I was too busy keeping up with measuring snow fall around Jackson and then analyzing and calculating what was coming for the next 2 or 3 days. It was an exhausting week of forecasting for sure!

Posted by Jim Woodmencey, meteorologist

Snow in the Future

2012-01-11T08:45:00.000-08:00

We haven’t really seen much change in the weather pattern over the Western United States over the last 8-weeks, with the exception the New Year’s Weekend storm. But, it finally, it looks like we’ll see some changes beginning next week. First indications that a strong Westerly flow will develop from the eastern Pacific across the Northwest U.S. and the northern Rockies.

A series of weather disturbances will be moving through this developing Westerly flow, with a Low pressure center hanging around the British Columbia Coast helping to supply colder air, and segments of strong jet stream cycling right overhead, should all add up to being a good longer-term snow producer, from the Cascades to the Northern Rockies.

Over the last 8 weeks we've seen a relatively dry weather pattern, most of the time the jet stream was way to the north in Canada, or it was split, or we were under a dry Northerly flow. None of which was very good for producing more than a few brief shots of snow.

Current Jet Stream Map

Finally, it looks like this developing weather pattern could persist for a period of 7 days or more. As it looks right now, we should see some snow beginning Monday & Tuesday of next week, and then the potential for heavier snowfall coming by the end of next week. With snow continuing through the following weekend (Jan. 21/22).

Forecast Jet Stream map for Jan. 20

Jet stream maps courtesy of IPS MeteoStar

Still A Ways Away...
Granted, this is still almost a week away, but at least the computer models and the longer range outlooks are giving us some hope for pulling out a decent January, snowfall-wise. (See the precipitation outlook maps below).

You can read and view more extended forecast and outlook info at www.mountainweather.com by going to the NWS Discussions & Outlooks Page.

6 to 10 Day Precipitation Outlook Map

8 to 14 Day Precipitation Outlook Map

Text by meteorologist Jim Woodmencey

Maps from IPS MeteoStar's LEADS Online
and NOAA

Winter Solstice

2011-12-20T16:26:00.000-08:00

The Winter Season officially begins Wednesday December 21st, 2011 at 10:30 pm MST. As we enter the Fourth Quarter of the Month of December, I know quite a few people in the Mountain West are wishing for snow, but please remember, I am not the Tim Tebow of meteorologists!

I'd like us to finish strong in December and come out ahead with a lot of fresh powder, but we'll probably fall short of most people's expectations.
The good news is, the weather pattern we've been locked into most of the month of December is showing signs of changing and the jet stream across the Pacific looks like it will begin directing some weather systems and some moisture across the Pacific Northwest & Northern Rockies on a more regular basis.
We've been in a split flow, with moisture getting directed north into Alaska & Canada most of the month, and also south across the Southwest U.S. (See jet stream map from 12/20/11).

DECEMBER 20, 2011 Jet Stream Map
Courtesy of IPS MeteoStar

Looking much better even as we head into the week between Christmas and New Years.
(See jet stream map for Christmas Night below). Much more of a Westerly flow across the Gulf of Alaska, and that is what we want to see. It's not quite the Super Bowl of weather situations, but it should get us back on track with more frequent snowstorms and salvage the season after a somewhat dismal start.

DECEMBER 25, 2011 Forecast Jet stream Map
Courtesy of IPS MeteoStar

More to come.......

Posted by meteorologist Jim Woodmencey
Maps from LEADS, IPS MeteoStar

Comparing La Nina's

2011-12-07T09:25:00.000-08:00

A fair mount of excitement was generated earlier this fall when word got out that we were going to continue with a "La Nina" again this winter. However, not all La Nina’s are created equal and this year’s La Nina is weaker than last years. Map comparing area of cold Sea Surface Temps (SST) around the Equatorial Pacific that defines a La Nina, below.

La Nina/ El Nino Review: La Nina means colder than normal SST's in the Equatorial Pacific, and El Nino means warmer than normal SST's. La Nina's usually keep the Northwest U.S. wet in winter and the Southwest U.S. dry. El Nino's usually have the opposite effect.

By now you may have noticed a difference between the amount of snow and the frequency of snowstorms that we’ve had this season so far, compared to the way we started last season with a bang in late October. The Winter of 2011-12 is not off to the same start as last winter, and that is consistent across the entire Western U.S.

Pre-season snowfall, October & November 2011, was actually still a little above average in Jackson Hole, but nowhere near the amounts seen pre-season in 2010. (See graph below left).

The biggest difference though between this time last year and right now is seen in the settled snowdepths at ski areas throughout the West. Snowdepths are much lower than they were in early December 2010. (See graph above, right)

Here in Jackson Hole I suspect most folks naturally expected a repeat of the “700 inch” snowfall winter we had last year during that “La Nina”. Obviously the possibility of that wish coming true dwindles with each passing day without new snow. Again.....not all La Nina's are created equal!

While a La Nina winter usually means that we will see above normal snowfall in the mountains (true for most Pacific Northwest and Northern Rockies mountain locations), it does not define how or when that snow will be delivered.

Part of that is controlled by where a Ridge of High pressure sets up in the Pacific and where the main storm track sets up to bring Pacific moisture inland. Last year most of the winter the High was set up perfectly and storms rolled across Pacific Northwest, Sierras, Northern & Central Rockies almost continuously. (Red line on Map).

This year the Ridge of High pressure, so far, as caused the storm track to take a more northern route up into Alaska. That has prevented the continuous train of Pacific moisture from coming directly across the Western U.S. (White line on Map).

Snow History in JH

If you look at it statistically, in Jackson Hole the mountains have an above average snowfall 70% of the time during a La Nina year. Last Winter’s La Nina was strong to moderate, more like 2007-08. This year’s La Nina is weaker, more like 2000-01. Both of those winter’s saw above average snowfall at the end of the season tally, but when the snow came was decidedly different.

Even if you look closely at the snowfall distribution at Jackson Hole (9500-ft. Rendezvous Bowl Study Plot) from last winter (2010-11) most of the snow came pre-season and post-season. The mid-winter snowfall was just average, December thru February.

(See Graph 1).

Outlook For Winter 2011-12

While La Nina conditions are still expected to continue thru the northern hemisphere winter, although it may take a little longer for the weather pattern to finally change for the better (snowier).

Right now it looks like there may be a more significant shift of that Ridge currently parked out in the Pacific, and subsequently see the storm track starighten out again across the Pacific by about the time we get to the Winter Solstice (Dec. 21).

Below are the 3-Month Outlook Maps for January-March 2012, and the signature is still that of a La Nina, colder and wetter Pacific Northwest and Northern Rockies. Note that the line of above average precip do not extend as far south into the Sierras and Utah/Colorado like it did last year. ("EC" means Equal Chances of above or below average).

Obviously we didn't see the pre-season snowfall that we had last year, and it’s unlikely we would ever duplicate the unbelievable post-season snowfall amounts that we saw last winter/spring. However, it would make sense to see a bigger mid-season snow than we had last year, and still make the Winter of 2011-12 come out above average.

This Blog entry was adapted from a presentation given by meteorologist Jim Woodmencey at the Avalanche Awareness Night in Jackson, WY on December 1, 2011.

Where is All the Snow?

2011-10-29T06:51:00.000-07:00

Usually by around Halloween skiers start thinking more about winter than they are about fall sports. If you remember last year at this time the Northern Rockies were already blanketed with 2 to 3 feet of snow between October 23 & 26, 2010 and people were backcountry skiing like it was early December.

Yesterday I took a mountain bike ride (while thinking about skiing!) with Chris Harder who told me he had skied “25-short” in Grand Teton National Park, to the valley floor, on October 28, 2010. What a difference a year makes.

This year, on October 25 & 26 the Central Rockies of Colorado got the big early season dump with 10 to 15 inches in 24 hours and more than 2 feet total in some locations this week. That storm extended from Wolf Creek in the Southwestern part of the Colorado Rockies all the way across the State to Eldora just outside of Rocky Mountain National Park in the northeastern part. (Map below shows snow depths as of Oct. 28, 2011 in Wyoming & Colorado)

Also, parts of the Northeastern U.S. have already had some pre-Halloween snowfall, from the Catskills of New York to the mountains of Vermont and New Hampshire (pronounced “New Hampsha”). They got good snow this past week also, albeit less than 10 inches in most places. The other area that was getting heavy snowfall this week was the mountains of British Columbia and into the Canadian Rockies.

Some skiers in the U.S. Northern Rockies might already be saying where’s ours? With all the hype about it being another “La Nina Winter” I think people expect a repeat of 2010-11. And while we may end up with an above normal snowfall winter again in Jackson Hole, the distribution of that snowfall may not necessarily be identical to last year, nor as continuous like it was from late October to late May!!. It’s already different than it was last year going into this winter.

Keep in mind as we go through the next 6 months, that no two La Nina’s are created equal.

Keeping Track of Who Has the Snow

If you are planning ski trips this winter you can keep track of where the snow is, across the entire USA and southern Canada by going to www.mountainweather.com and getting on the Skier’s Page under the "Additional Mountain Weather" drop-down menu.

Here you will find links to ski areas throughout the US, with a concentration of links and more information for western U.S. ski areas. Also links to the latest Avalanche Advisories are midway down the page, for the backcountry skier.

At the bottom of the page is where you’ll find snowfall and snowdepth info in more detail. (An example of the National Snow Depth map is shown below).

There is also a link in the Quicklinks box in the upper right hand corner of the Skier’s Page that will take you to the National Snow Analyses page that is updated daily by NOAA.

If you are a real snow-nerd, you can keep up with everything from snow depths, to snow-water equivalent, to sublimation throughout the early season and over the course of this winter.

Posted by meteorologist Jim Woodmencey
October 29, 2011

First Snow of the Season!....and La Nina Update

2011-10-07T08:00:00.000-07:00

It has arrived, the first snow of the season, and it is only Oct. 6^th. An unusually cold Low pressure system covering most of the Western U.S. with a huge counter-clockwise circulation around it, brought snow this morning to the valley floor in Jackson Hole. Generally about 2 inches in the valley, with maybe 6 inches at higher elevations, but not too much more than that at this point (end of day Thursday). But before it is done later Friday, there might be 10 or 12 inches at higher elevations in the Tetons.

This storm began putting down some decent snow in the Sierras the day before. And temps were cold enough aloft to bring snow down to fairly low elevations. Even Salt Lake City at 4500-ft. had a couple of inches of snow today.

This is all coming after about a ten-day stretch of nice Indian Summer weather in late September and high temps in Jackson hitting 80 degrees just one week ago!

Below are some pics from webcams around the region showing the new snow today:

Town of Jackson & Teton Pass

Sun Valley, ID & Snowbird, UT

Compared to Last Fall

Last year we had our first good snowfall in the mountains on September 10^th, with almost 12 inches at 9,000 to 10,000-ft. in the Tetons, but snow levels only reached down to around 8,000-ft.

Then it went warm and dry for a month, until October 23^rdwhen it snowed to the valley floor and ended up throwing down 2 to 3 feet at the higher elevations over the course of 4 days. And of course the rest of last winter is legend. It never really stopped snowing until sometime in June!! “Viva La Nina”, the skier’s chanted.

Well, it looks like they may get their wish…….

La Nina Update

The latest update to the ENSO forecast came out today…………read all about it first hand by going to the bottom of this page ….NWS Discussions & Outlooks ….and click on current the ENSO Discussion or peruse the long range outlooks or go to the La Nina page and learn more about the phenomena to impress your friends during Apres Ski.

The short of that report is: La Niña conditions are expected to gradually strengthen and continue through the Northern Hemisphere winter 2011-12.

It goes on to say that this one is not as strong as last year’s La Nina.

So, while it may not be as strong, it is at least showing a trend of sticking around through the winter, which should be good news for a more northerly storm track that favors the Northwest and Northern Rockies especially.

We will forever equate last year’s La Nina with bountiful powder that went on and on into the spring. That will be what we expect all La Nina’s to do. And that is simply not the case. Just like the proverbial snowflake, no two La Nina years are ever exactly alike, but the odds at least favor an above normal snowfall winter.

The Outlook for this Winter

2011-09-05T08:24:00.000-07:00

This time of year the most popular question I get asked is, “What kind of winter do you think we’ll have?” My standard response is, “Snowy!”

The real question though on everyone’s mind is, exactly how snowy will it be? After all, more snow equates to a better ski season.

So, the real quest is to try and give everyone a heads-up on how early will the snow come and will it keep coming right through the whole winter season…..and then somehow magically stop on April First, when we want the weather to turn to spring. By that time of year, the question becomes, when is it going to get warm and sunny?!!

Long Range Outlook

There are a number of sources for long-term weather forecasts, most of which are pretty general, that is, they only say if it’s going to be warmer or colder than normal, drier or wetter than normal.

The Farmer’s Almanacs for 2012 will be coming out soon, and there are several versions these days, which each have their own secret formula for predicting the next year’s worth of weather. But if you read them closely, they hedge back and forth to cover a variety of possibilities, and they can be confusing or misleading about what is going to occur. The regional seasonal forecasts don’t always jive with the specifics of the monthly/weekly breakdown.

On the NWS Discussions & Outlooks page of mountainweather.com I have put together a collection of Long Range Outlook information that you can peruse. These include 6 to 10 day outlooks, 8 to 14 day outlooks, 30-day and 3-month seasonal outlooks. Then, if you click on the link in red to “Climate Prediction Center Seasonal Outlook Page”, you can get an outlook for the next 12 months…..right through September 2012.

This year’s early fall outlook, September through November, for precipitation over the northern Rockies is “EC”, which means “equal chances” that we will experience above, below, or normal conditions. Oh, that’s helpful. Only the far Pacific Northwest Coast is expected to be wetter than normal.

Temperatures between now and November are also in the EC range for the far northern Rockies, to warmer than normal for the central and southern Rockies.

As we get into the meat of winter, December through February, precipitation for the northern and central Rockies remains at "EC", and only the Pacific Northwest, now including Northwest Montana is shown to have above normal precip.

The Pacific Northwest is also shown to be colder than normal for this time period (see maps below). Could that spell a winter of drier, lighter, powder for the Cascades? That would certainly be an anomaly!

Precipitation Map below for December-January-February

Temperature Map below for December-January-February

Keep in mind these are general “outlooks” over 3 month periods, not spot-on “weather forecasts” of big snowstorms or drought. They are general trends based on a bunch of different computer models and inputs. Subject to change as the weather actually changes!These get updated on an almost weekly basis.

At the bottom of the page is information about El Nino/La Nina. Most skiers are very in-tune to this phenomena, and I think it helps keep the world simple for them……La Nina means lots of snow and El Nino doesn’t.

Winter 2011-2012 Outlook

Simply put, last winter we had La Nina conditions all fall, winter, and into spring and it was very snowy from October through May. La Nina did what she was supposed to for the Northwest and the Rockies, even the Sierras, where she wasn’t supposed to!

Currently we are under what is known as a “Neutral” condition, neither El Nino nor La Nina. In other words, sea surface temperatures in the equatorial Pacific are normal.

The latest prediction is for that to continue this fall and then either stay Neutral for the winter or trend towards a La Nina again. And a new forecast comes out this week….so stay tuned.

Last winter’s La Nina was a strong one, and for us to get another winter like we had in 2010-2011 would be pretty hard to beat, or repeat.

Bottom-line is, when you look at all the outlooks, it seems like we are in for what might be considered a “normal” winter in the northern Rockies and Jackson Hole.

Essentially at this point to say we’ll have a snowier than normal winter or a drier than normal winter would be throwing a dart. Saying it’ll be snowier than normal will sell more season passes pre-season. Saying drier than normal will only bum out the ski crowd pre-maturely.

My experience has been that most folks will put their faith in whichever forecast is predicting the kind of weather they want to see happen. And they hang their hat on that almanac, or that outlook, or that La Nina forecast.

One thing I can say with some certainty, at some point this winter season it will be snowy! And at some point someone will ask, when is it going to stop snowing?

New Lightning Map for Jackson Hole

2011-08-06T06:05:00.000-07:00

The Lightning Detection system I spoke of in the last MountainWeather Blog is now up and running and working pretty well. “Live” lightning strike data is now available for Jackson Hole and it can be viewed by going to mountainweather.com and clicking on the Lightning Map under the Jackson Hole drop down menu. Or, just click this link: Lightning Map.

Sample Map from this past Thursday Night's Thunderstorms, before they hit Jackson.

Reading the Maps

If you open another browser page along side this one, I will guide you through how to read and interpret these maps. Once you have the Lightning Strike Map page open, you will find two maps on this page………. Along with local satellite and radar map sat the bottom.

The top map is a “static” map or a “screenshot” that is zoomed out to 63 miles from the center. The white rings are in miles from the center, and the center of the map is right over the top of Snow King Mountain, just above the Town of Jackson. The large red ring is the 50-mile mark, out from center.

The lower map, further down the page, is an “active” map that goes out to 180 miles from center. It has some user controls that allow you to zoom even further out, to have a look beyond 300 miles. What you see out that far though is unreliable. From the testing done over the last month or so, I have found the useful range of this instrument to be between 120 and 150 miles. Beyond that, the accuracy of strike placement and detection of all strikes is inconsistent. This system has been working really well tracking the location of strikes and thunderstorm intensity within a 60 to 75 mile radius.

The symbols on these two maps are roughly the same. Big red dot is a recent negative ground strike and big orange dot is a recent positive ground strike. Most important difference between the two is the positive ground strikes are much more powerful, and are usually the strikes that kill people or start fires.

The + and – symbols are in-cloud lightning flashes, either between two clouds or within a single cell. These bolts are not striking the ground, but they may be an early indication that a thunderstorm is developing.

All of these symbols become smaller dots on the map after a minute and a half (90 seconds). The small dots are old strikes, both ground and in-cloud.

When a cluster of strikes occur in the same vicinity the TRAC system kicks in (Thunderstorm Ranging and Acquisition) and analyzes the thunderstorm and tracks its progress and intensity. These will appear as green, yellow, or red circles on the map indicating the approximate location of the thunderstorm and its strength, weak, moderate, or strong thunderstorms, depending on how much lightning they are producing.

Alert and Warning System

Right now, Snow King Mountain uses this information to make decisions about when to stop loading the summit chairlift. The software used with this sensor has an alarm system built in that is pre-set to 50 miles (thus the red ring on the map). Whenever lightning is detected anywhere within this 50 mile radius, an e-mail alert is sent out to the chairlift operations workers at Snow King. In this alert message the bearing (compass direction from town, the strength of the storm and whether it is intensifying or not, are all indicated in the message.

Like I said before, this sensor and these maps in no way assure that you will be magically protected from lightning strikes. It does provide you with a useful tool that can increase your ability to take some action to avoid dangerous lightning that might be approaching.

Special thanks to Snow King Mountain fro throwing some money at this project to see if it would work, and to Adam Shankland and his crew at Snow King for helping with the installation and adjustments this past month, one time with thunderstorms knocking at the door!

Also a big thanks to AJ Best of Gliffen Designs for doing all the programming and networking work that had to be done to be able to publish these maps “live’ on the internet.

Feel free to contact me if you would like more information about this sensor, or the alert system.

Jim Woodmencey

Meteorologist

307-739-9282

Lightning Safety

2011-07-21T10:32:00.000-07:00

It was one year ago today, July 21^st , 2010 when a series of thunderstorms pounded the Grand Teton with an abundance of lightning, injuring 17 people, and causing the death of one other climber when he was knocked off the mountain. The amazing story of this incident and the ensuing rescue of the victims have been retold in this week’s issue of Sports Illustrated magazine, in an article by writer Brad Wieners. A link to that article on-line can be found here:

July 18, 2011 Sports Illustrated: Countdown to Tragedy, by Brad Wieners

During the summer months in the mountains, lightning is probably the greatest weather hazard we face when recreating. You don’t have to be climbing the Grand Teton (with a backpack full of metal objects, no less) to be struck. Even though the Grand is the absolute highest point around and your odds are considerably increased, it is also possible to be struck by lightning in the valley, on the baseball or soccer field, out on the lake or the golf course, as well.

It has been an ongoing challenge of mine to educate as many people as possible on the subject of “Thunderstorms and Lightning Safety”, and I will outline at the end of this article the most important things to watch for when you are outdoors this summer.

Lightning Detection System

I have also been working on a project to install a Lightning Detection System for the local area. This has been a cooperative effort between MountainWeather and Snow King Mountain to provide an early warning of approaching thunderstorms, and their dangerous lightning.

This project was originally conceived to help make the summer operations at Snow King a little safer. Although, you must keep in mind, this is a lightning detection system, not a lightning prediction system. It is only capable of plotting strikes that have already occurred.

Just before the Fourth of July Weekend, Adam Shankland of Snow King, AJ Best of Gliffen Design (my IT guy), and myself installed the instrument at the top of Snow King. Since then we have been able to test, re-configure, and retest the system over the several days of thunderstorms that we have experienced over the course of the last few weeks. It seems now like it is working well enough that I am almost ready to put the lightning map on the website and make it available to the public on the mountainweather.com website (it will be under the Jackson Hole drop down menu).

This instrument can detect lightning strikes out to a radial distance of approximately 200 miles, less in some directions and further in other directions. This variability is due to the complex mountainous terrain that surrounds us here in western Wyoming.

Not only will this instrument detect dangerous ground strikes, but it will also detect in-cloud lightning bolts, which often are the first indication of lightning activity in thunderstorm clouds. All of this information gets plotted on a scaled map, with distant rings out to a radius of 300 miles.

When this information gets linked on the mountainweather.com website I will make an announcement here on the MountainWeather Blog (and on Facebook). At that time I will let you know how to interpret the information, what its limitations are, and how to best utilize the map. There will also be an opportunity to receive e-mail warnings from this system (for a small monthly fee), so that you can receive fair warning when lightning is in the area, even if you can’t see it or hear it. That will be handy for those times when you are actually outdoors and not glued to the lightning map on the computer!

While this project in no way assures that you or your property will be magically protected from lightning strikes, it does however provide you with another tool to perhaps increase your ability to avoid dangerous lightning. More on this project soon….

Thunderstorms & Lightning Safety

· The earlier in the day clouds start building; the earlier in the day thunderstorms can occur.

· The more cumulus cloud there are covering the sky, the better the chances of developing larger and more dangerous thunderstorms.

· The taller the cumulus clouds are, the more likely they will produce a thunderstorm.

· The darker the base of the thunderstorm, the taller the thunderstorm is, and the more likely it is to produce a heavy downpour of rain and/or hail. Very dark bases over a very broad area indicate potentially more violent thunderstorms, with strong wind gusts or even tornadoes.

· The “scattered sheep” or “fair weather” cumulus type clouds never develop vertically very much.
Their bases stay white all day, rather than turning gray, and they do not pose a threat.

· Prime time for thunderstorm development is mid-afternoon to early evening (2 p.m. to 7 p.m.). Nocturnal (nighttime) thunderstorms are usually the result of a storm system or a cold front passing. Or, they may be related to “monsoon” moisture coming up from the south, usually in July & August.

Lightning

Timing Lightning to Thunder: Lightning travels at the speed of light. Thunder travels at the speed of sound. Therefore, lightning is seen before the thunder is heard.
You can time how far away the lightning is by counting, in seconds (one-thousand-one, one-thousand-two, etc.), from the time you see the flash, until the time you hear the thunder.

Take the number of seconds and divide by 5 to calculate the distance the lightning is from you in miles.
Seconds Counted / 5 Seconds per mile = Number of Miles Away.

25 seconds = 5 miles away. 5 seconds = one mile away. 1 second = less than a quarter mile away.

(Note: Thunder can only be heard up to about 10 miles away, maybe 15 miles away on a good day!)

· Get away from metal objects, including fences, hardware or machinery, chairlifts, golf clubs, etc.

· Never stand under a lone tree. Being in a grove of trees of similar height is a better option.

· Get off the ridgetops, get out of open fields, get out of the water!
Swimming or boating is also very dangerous during thunderstorms.

· If you are on an exposed ridge: sit on an insulated pad or backpack. Be sure you are not in a natural water course, like a gully, these will conduct ground currents when bolts hit nearby.

· Retreat to a building or car, lie down in a dry ditch, or try to lie as low as possible.

· The most dangerous time for a fatal strike is before the thunderstorm is right over you. Lightning usually precedes heavy rainfall. It does not have to be raining to be struck by lightning

Lightning has been known to strike the ground from over 5 miles away!

The 20/20 Lightning Rule: If the time between the lightning flash and the thunder is 20 seconds or less, then the lightning bolt was less than 5 miles from your location. It is time to seek shelter IMMEDIATELY!
After the last lightning bolt is seen, give it about 20 minutes until you return to any exposed area.

Note: Ideally, this would be more like a 30/30 Rule. But there aren't many folks I know who will seek shelter that early, or hang around that long before they go back out. So, 20 minutes is a compromise

Adapted from Reading Weather, by Jim Woodmencey

Click here to get a PDF of this to print

The Summer Monsoon Explained

2011-07-09T09:08:00.000-07:00

We were getting a little bit of moisture from the Desert Southwest Monsoon this week, causing some thunderstorms around the area. And it looks like we may get another surge of that monsoon moisture again this coming week.

If you happen to listen to my forecast rap in the mornings on the radio (KZ95 95.3 FM & KJAX 93.3 FM) you will frequently hear me mention “monsoon moisture”, during the summer months. In this week’s blog entry I’d like to explain exactly what that means.

The term “monsoon” comes from the Arabic word mausim, which means “a season”. It refers to the large-scale wind flow that lasts for a whole season near the Indian Ocean and the Arabian Sea.

A "monsoon", therefore, is simply a seasonal wind flow pattern. The Desert Southwest Monsoon that occurs in the United States is similar to the Asian Monsoon that affects India and the Himalayas during this same time of year, from July to early September.

The North American version of the monsoon originates over the interior of Mexico, where very moist (i.e. humid), tropical air is converging over the land from the Pacific Ocean to the west and from the Gulf of Mexico to the east. That moisture is then drawn northward by southerly winds over the hot, dry deserts of the Southwest. This causes frequent strong thunderstorms over New Mexico and Arizona.

Often in July and August the monsoon will surge up into Utah and Colorado, causing thunderstorms over the deserts of southern Utah and western Colorado. Some of these thunderstorms create flash flooding situations in the canyon country of the Southwest.

A few times a summer that monsoon moisture will reach as far north as Northwest Wyoming and Southwest Montana, causing thunderstorms here, which are often some of the strongest of the summer season.

The typical weather pattern that sets up in July and August that will bring transport the monsoon moisture this far north is when a thermal Low pressure (dry low pressure caused by heating) develops over southeast California and western Arizona, at the same time High pressure develops over eastern Texas. Then when a Low pressure system or upper level Trof of Low pressure moves into the Northwest U.S., that helps draw that monsoon moisture northward. (See example map below of this weather situation).

Difference in Type of Thunderstorms

Monsoon-related thunderstorms are a little different than the more typical summertime, afternoon thunderstorms that we have engrained in our memory banks. These more typical afternoon thunderstorms are known as “airmass” thunderstorms, which develop due to the convection caused by afternoon heating.

Whenever there is enough moisture and instability in the atmosphere (that varies from day to day) cumulus clouds will develop as the ground gets heated by the sun in the afternoon. These airmass thunderstorms, or garden variety afternoon thunderstorms, will occur between 2:00 PM to 5:00 PM, or sometimes into the early evening hours.

Thunderstorms generated by the monsoon can occur anytime of the day or night. They are more random in nature, kind of like a drive-by shooting, you never quite sure where or when they are going to hit.

This makes for a challenging forecast situation, as the development of thunderstorms is dependent upon whether or not that monsoon moisture gets over your location. Often times we end up on the very northern edge of that moisture here in Jackson Hole, with thunderstorms just south of us.

Monsoon Surge July 5th to 7th, 2011

Last week was a good example of that in action. Tuesday we got a surge, and had thunderstorms in the south end of the valley, but nothing really north of the Airport.

(See the Satellite Imagery in the graphic, click image for loop from Tuesday afternoon.)

On Wednesday, the monsoon moisture retreated a little further south and we had no thunderstorms here. Thursday and early Friday it surged back up and got close, with a few thunderstorms nearby.

Announcing the Launch of New JH Forecast Format!

2011-06-22T05:12:00.000-07:00

Today, Wednesday June 22nd is the first full day of Summer 2011. With this change of season comes a new format for the Jackson Hole Forecast on www.mountainweather.com

This is the first major revision of the forecast format in several years, and hopefully it makes for an easier to use and more visual experience.

Take some time to get oriented to the new layout. There is all of the same information you are used to getting, but now it is also displayed in a graphical format.

Mountain temps and ridgetop wind forecasts now go out 5 days instead of only three. The thunderstorm and lightning forecast also goes out 5 days. In the winter, that will be replaced with the snowfall forecast, which will also go out 5 days.

Sunrise/sunset times are now listed for the next 5-days, so you can track when the days start getting shorter! (Ugh)

The only thing missing right now from the old version, is the moon phases. We are still working on how to best fit that info on the page.

There is a printable version from the website that includes everything down to the 3-Day Weather Forecast Description. This is free to print and display at you place of business for visitors to read. (Saving your employees countless time not having to answer the question, "what's the weather going to do?").

The e-mail version of the forecast, which includes all the forecast information you see on the web, plus a detailed weather discussion and extended outlook written each weekday morning by meteorologist Jim Woodmencey and sent out to your e-mail address (that discussion does not appear on the website). The e-mail version will still be available to those customers who currently subscribe.

For more information about receiving the e-mail version, or any questions or comments you may have on the new format of the forecast, feel free to e-mail me or call at:

jim@mountainweather.com

307-739-9282

JH Forecast by meteorologist Jim Woodmencey

New layout created by AJ Best of Gliffen Designs in Jackson, WY

Nine Months of Winter

2011-06-19T11:08:00.000-07:00

There’s an old saying about the seasons in Jackson Hole, “We get nine months of winter and three months of bad skiing”. Which would apply to most ski towns in the Rocky Mountains and the Western U.S. this year.

Fact of the matter is, the first snowfall in the Teton Mountains came back on September 10, 2010, and it is now June 19, 2011, and still snowing at the higher elevations today. There is still about 10-feet of snow on the ground above 9500-feet in the Tetons, which means there might be more like only 1 or 2 months of bad skiing this year. (Current snowdepth map for the Central Rockies).

Spring Ends

The Summer Season officially begins on Tuesday, June 21^st If all goes well, temperatures will crack 70 degrees by Tuesday afternoon, something that has only happened a handful of times this spring in Jackson. And, as if someone flipped a switch, it looks like the first week of summer will be warm and dry, with highs remaining in the 70's all week.

Normal high temperatures for this time of year would be mid 70’s. The record high in Jackson on the Summer Solstice is 90 degrees, set back in 1994.

This June so far, we have seen cooler than normal temps most days. There was that one weekend when we almost hit 80 degrees (June 5 & 6). But then it snowed in town on June 9^th and the high was only 50 degrees (record cold max temp for that date). And it looks like it will be another well above normal precip month, as well.

So, while we never really had a fall or a spring season, we can at least hope for a few weeks of summer this year.

The Solstice

The exact time of the Summer Solstice on Tuesday June 21, 2011 is 11:16 AM MDT. This is when the sun will be directly over the Tropic of Cancer at 23.5 degrees North latitude.

The Solstice also marks the longest day of the year in the Northern Hemisphere. But the days don't start getting shorter for about another two weeks, as the sunrise/sunset times do not change much around the Solstice.

We will have almost 16 hours of daylight in Jackson the rest of the month -- not including twilight -- compared to less than 9 hours around the Winter Solstice in December.
The graphic below shows the change in the tilt of the earth and its orientation to the sun, which is responsible for the seasonal changes we normally see. As you can see, in the summer, the northern hemisphere is tilted towards the sun.
So, when the sun finally does appear from behind all the clouds, it will be as high in the sky as it gets around here, about 70 degrees above the horizon at noontime.

text by meteorologist Jim Woodmencey

Coldest May on Record in Jackson

2011-06-11T10:03:00.001-07:00

May Weather Review

Probably to no one’s surprise, the May 2011 was the coldest May on record in Jackson, WY. Historically, the average mean temperature in May comes out to be 47 degrees. May of 2011 the mean temperature was 38.5 degrees. Almost 9 degrees colder than normal.

The old record coldest May was back in 1953, with a monthly mean temperature of 41.6 degrees. We blew that away by just over three degrees.

Mean temperature is simply the average of the monthly average high and low temperatures, and is perhaps the best measure of how much cooler or warmer we are compared to normal (historic averages).

May Temperature & Precipitation Data for Jackson, WY
	May 2011	Normal	Departure from Normal
Avg. High Temp	50°F	63°F	- 13°F
Avg. Low Temp	27°F	31°F	- 4°F
Mean Temp	38.5°F	47°F	- 8.5°F

Total Precip	2.63 in.	1.88 in.	+ 0.75 in.

Precipitation

Precipitation-wise, while not the wettest ever, it was wetter than normal in Jackson in May 2011 with 2.63 inches of water recorded at the Jackson Climate Station. The month of May is, after all, the wettest month of the year in Jackson, averaging 1.88 inches of precipitation. Record precip in May is 6.02 inches, set back in 1980.

You can see all the monthly averages on the JH Climate page on mountainweather.com

This page is still a work-in-progress and I hope to add more climate info and seasonal descriptions and weather history info to this page soon. But the weather this year has been keeping me too busy!!

Mountain Precipitation

Below are precip maps for the Month of May 2011, for the Western U.S. and for Wyoming. From these you can see the Tetons, Bighorns, and Wind River Range mountain ranges received somewhere between 6 and 12 inches of precipitation during the month of May 2011. Most of that came as snow at elevations above 8 to 9,000-ft.

As a matter of fact, snow depths in the Tetons on June 1, 2011 were still over 12 feet deep. At Jackson Hole Mountain Resort at th ebottom of Rendezvous Bowl at 9580-ft. snowdepth June 1 was 158 inches. On April 1, 2011 it was 142 inches. It is now June 11th and the settled snow depth this morning was 143 inches.

That is what is truly amazing, when "normally" this time of year we are losing snow....this year we have yet to lose an inch.

Text by Jim Woodmencey, meteorologist

Snowmelt, Water, and Flood Potential

2011-05-26T10:24:00.000-07:00

This week I will highlight all the various sources of snowpack, water, and flood reports available via the internet so that you can stay on top of the run-off conditions this Spring. Most of these sources of information can be found on the www.mountainweather.com site, with a little poking around. Information specific the Jackson Hole region will be highlighted, but links to snow, water, and flood information for the rest of the U.S. are also included.

Snowpack

There are two ways to look at the snowpack that remains in the mountains and how it compares to average. One is the Snow Water Equivalent (SWE), and the other is Total Precipitation.
(from the JH Information page go to "Snowpack Information", which takes you to this page...
Snow-Precipitation Update).

Both SWE and Total Precipitation numbers are shown for the various river drainages in Wyoming. For the rest of the Western U.S., scroll down to the bottom of the Skier's Page and click on the Western U.S. Snotel map to generate similar data or reports.

SWE shows the percent of average snow water that still exists, as of this date. Most of these numbers are extremely high, because normally by this time of year we are losing snow, or in some locations most of the snowpackdown to next to nothing or is already completely gone.

In the Snake River Drainage, SWE is at 232% of average for this time of year.

This year, the snowpack has declined very little since mid-April (when it reached its peak) at the higher elevations. Even mid-elevation snowpack is way more than what it normally is at the end of May. And it looks like we won't lose much through the Memorial Day Weekend. As a matter of fact at higher elevations we'll likely be gaining some snow!

Snowdepths at JHMR May 26: Rendezvous Bowl = 159 in. & Mid-mountain = 97 in.
Snowdepths at JHMR April 3: Rendezvous Bowl = 142 in. & Mid-mountain = 108 in.

Precipitation totals for the water year (which begins October 1^st) are perhaps a better gauge of how much water we have had this winter, used, in combination with how much water is actually in the snowpack that has yet to melt.

Snowdepths in the Tetons, around Togwotee Pass and Yellowstone Park between 8000 and 9500-feet are still between 75 and 150 inches (@ 6 to 12 feet deep!).

In the Snake River Drainage, Year-to-date Total Precipitation is at 130% of average.

Water Content of that remaining snow in the surrounding mountain ranges is between 30 and 50 inches.

Water

Reservoirs and streams are already pretty full in most places across Wyoming and Idaho, with still some room left for more water from run-off in Jackson Lake and Palisades. This info can also be found on the JH Information page.

Another way to look at the stored water is the Surface Water Supply Index (SWSI), which is a combination of water in reservoirs and the forecast run-off. For Wyoming, these number are very high, which simply means we are very wet. (See SWSI Map).

Flooding

The National Weather Service’s Hydrological Prediction Service keeps track of river levels and makes forecasts for flooding potential. There is also a lot of information available about river flows and flood forecasts for eastern Idaho & Wyoming on the JH Information page, or nationally from the River Forecast Center website.

Text by Meteorologist Jim Woodmencey

Springtime Avalanches and Landslides

2011-05-18T04:29:00.000-07:00

Wet snow and mud slides in May are not an unusual occurrence, especially after a big winter’s snowfall that is followed by a very wet spring. Bare ground or a snowpack that is being saturated with water due to melting snow become well lubricated and poised to move downhill.

Big landslide and snowslide events have been responsible for closing roads around the Yellowstone and Jackson Hole area this May.

On Sylvan Pass in Yellowstone Park a cycle of wet slab avalanches blocked the highway with avalanche debris up to15 feet deep on May 11th, 2011. While I am still in the process of investigating all the details of the snowpack and weather leading up to this event, it seems that the sequence of events that provoked these slides goes something like what is described below.

Avalanche Weather

Rain and warm temperatures at the beginning of April were followed immediately by colder temperatures, forming hard crusts up to around the 10,000-ft. elevation. That was followed by heavy snowfall the second, third, and into the fourth week of April. Temperatures then warmed in early May,reaching a peak around 50 without refreezing overnight at the end of the week, with more wet snow and rain May 6th to 8^th.All that new snow from April & early May was warming and it is likely that free water was able to percolate down to the rain-crust layer that formed in early April, providing a well lubricated sliding surface for the avalanches to run on.

(See more Spring avalanche photos from around the Tetons at Bridger-Teton Avalanche Center site by starting here: Snowpack Summaries with avalanche photos

Landslide Weather

As far as the landslide down in the Snake River Canyon, this is the second major slide in the canyon this spring. An earlier slide on the opposite side of the river did not affect the highway and was given little attention. The one that occurred this past weekend (May 14^th and 15^th), was also likely provoked by the weather this spring.

Overly saturated ground from melting snow from an above normal winter snowpack, compounded by much above normal precipitation in April and early May, further saturated the soil, and is what likely set that soil in motion. I would defer to the geologists to further explain what exactly is going on with the soil and rock strata down there in the Snake River Range. (see quote below). But without a doubt, excess water on the ground this spring contributed to the movement.

(See more about this landslide and more photos on Jim Stanford's site at JHunderground.com).

Note: Wally Ulrich, Wyoming State Geologist, just sent along this explanation of the geology in the Snake River Canyon area to me (May 19, 2011):

"The stratigraphy is filled with clay layers and the overthrust has bent and folded layers onto complex structures. Erosion exposes the dipping folded structures. Resistant layers act as boundaries, water as lubrication & gravity energy.
Tilted beds and a dipping anticline contribute to the present landslide."

May 1997 vs. May 2011 Landslide

You may recall that there was a similar large landslide in the Snake River Canyon back in May of 1997, almost to the day, on May 18^th.

I thought it would be interesting to look at the weather in the Winter & Spring of 1996-97 and 2010-11, to help explain how it may have contributed to setting these landslides in motion.

While both years had way above normal snowpack going into the spring..... April-May 1997 and April-May 2011 had completely different weather conditions.

April & early May 1997 was drier and warmer than normal (below normal precipitation, above normal temps). The week prior to the May 18, 1997 landslide we were had highs in the 70’s in Jackson, and one day with just over ¼ inch of rainfall between May 16 & 17.

April & early May 2011 was wetter and cooler than normal (way above normal precipitation and below normal temperatures). The week prior to the May 15,2011 landslide we had only seen a few days that got over 60 degrees in Jackson, but we had almost 2 inches of rainfall. That on top of about 3 inches of rainfall in the month of April 2011.

Forecasting vs. Backcasting

The important thing to keep in mind with both wet snow avalanche and landslide events of this magnitude is, that they are both extremely hard to forecast for. It is easy to “backcast” after they occur and point to specific weather that likely caused the massive failures, but beforehand, it is purely speculation that they could occur. And certainly pin-pointing exactly where they might occur is even more difficult.

Text by Meteorologist Jim Woodmencey

Photo of Avalanche in Yellowstone courtesy of NPS and Brad Ross

Photo of Landslide in Snake River Canyon from Steve Owens

Wet and Wild Weather in April & Early May

2011-05-11T08:31:00.000-07:00

With precipitation records being broken in many parts of the country this past April, and severe weather events that included devastating tornadoes in the Midwest and Plains, flooding along the Mississippi and many other rivers, all in all it was a wet and wild April to behold.

Map of Total Precipitation amounts across the US for the Month of April

It probably comes as no surprise then that April 2011 was wetter than normal in Jackson Hole, as well.

As a matter of fact it will probably go down as the "wettest" April on record here. While I do not have the "official" numbers yet from the US Forest Service's manually read climate station, I do have the numbers from the automated weather station that is located right next to the official climate station instrument shelter.

Jackson, WY Weather Stats for April 2011

· Total precipitation for the Month of April 2011 was just over 3 inches.

· Average April precipitation is 1.12 inches

· Record precipitation is (was!) 2.66 inches (April 1963)

· Average High temperature in April 2011 was 45 degrees, normal high is 52.

· Average Low temperature in April 2011 was 28 degrees, normal low is 25.

· Average Mean temperature in April 2011 was 36.5 degrees, normal mean is 38.5

· The warmest temp we had in April 2011 was 59 degrees on April 2^nd .

· The coldest temp we had was 15 degrees on April 23^rd.

Cool and Soggy Start to May

The Month of May started out quite wet also, nearly reaching our average precipitation for the month in the first 10 days of the month. The automated rain gauge recorded 1.80 inches through May 10^th. The average precip in Jackson in May is 1.88 inches. May, by the way, is normally the wettest month of the year, on average.

According to the thermometer at the weather station, we’ve only had one day so far in 2011 that has topped 60 degrees (Cinco de Mayo).

All that will be changing this week, with drier weather, more sunshine, and temperatures getting into the 60’s………for more than just one day!

Mountain Snowpack

While we’d normally be seeing the snowpack shrinking in the mountains this time year, we’ve actually still been accumulating snow, and settled snowdepths above 8,000 feet have held there own the last month or so.

The Tetons, Wasatch and parts of the cntral Colorado Rockies all have plenty of snow remaining in them this spring. See maps below.

Maps of Snow Depth and Snow Water Equivalent (SWE) for WY-UT-CO region.

The settled snow depth at the bottom of Rendezvous Bowl at JHMR (Elevation 9580-ft.) on April 1, 2011 was 142 inches. It was also at 142 inches on May 10, 2011.

Snow depth at the Phillip’s Bench SnoTel site on the east side of Teton Pass (Elevation 8200-ft.) stood at 95 inches on April 1, 2011. It was at 100 inches on May 10, 2011.

There is also 43.70 inches of water still contained in that snow yet to melt.
You can reference all the snowpack info for the U.S. by going to the bottom of the Skier’s Page on mountainweather.com

Direct link: http://www.mountainweather.com/index.php?page=skiers_page

Brace yourself for the run-off that is yet to come!

Avalanche Education for the Military

2011-05-03T06:55:00.000-07:00

While on my spring break this past week I had the distinct pleasure to be able to work with some members of the United States Air Force Combat Weather Unit on an avalanche course here in Northwest Wyoming.

Arriving on the heals of one of the biggest winters ever in

Jackson, and still experiencing “full” winter conditions through the last week of April, eight Air Force meteorologists assigned to a special unit at Hurlburt Field in Fort Walton, Florida made the trip to Jackson, WY for seven days of avalanche instruction.

This was a Level I & II avalanche course that was coordinated through the American Avalanche Institute and co-instructed by myself and John Fitzgerald, along with Don Sharaf adding a lecture on Snow Hydrology. The purpose of this course was to teach these guys as much as we could about avalanches and snowpack stability evaluation, skills they need when operating in mountainous regions like the Hindu-Kush in Afghanistan & Pakistan.

The extended winter weather enabled us to experience more January-like snow conditions rather than the spring skiing one might expect this time

of year. While trying to slowly break these guys in from sea level to our altitude, we marched them all over the Teton

Pass and Togwotee Pass areas for seven days in a row. As you would expect from combat ready soldiers, they were up for the task and took on the lack of oxygen with gusto.

By the end of the week they were pushing uphill with heavy packs at over 10,000-ft. as if they were back on the beach running through the sand rather than deep snow.

And deep it was, with new snowfall on several of the days, making for great powder skiing. And settled snowdepths in most place above 9,000-ft. in the mountains exceeding 12 feet, which made digging all the way to the ground an almost impossible task.

The odd thing about this season’s snowdepth is, that it is almost as deep up at Togwotee Pass as it is in the Tetons. Normally, Togwotee might see only half or, two-thirds of what the Tetons have. Not so this year, it’s almost the same across the board.

Temperatures most of the week were way below normal as well, starting the week (over Easter weekend) in the single digits in the morning at 10,000-ft. And ending the week with temps in the teens. On April 29^th I got out of my truck on Togwotee Pass at 13 degrees at 10 a.m. and when I returned at 5 p.m. it had warmed up to 15 degrees! Winds at ridgetop level that day were a steady 30 with gusts to 50. Nice day.

I have to say this was one of the best avalanche courses I have ever been a part of. It was an honor for me to be able to be out in the mountains with fellow meteorologists and share my knowledge of snow and avalanches with them.

It was also an honor to be in the company of such a distinguished and unique group of servicemen. These guys are not just sitting in a weather office staring at a computer, they are deployed to places like Afghanistan and often have to put down the hand-held anemometer and pick up a gun to help defend our freedoms. I thank them for that.

I only wish I could have still been with them this past Sunday evening when news came in that Osama Bin Laden was KIA. I’m sure

that would have been a time!

I salute all you guys for the job you do, and if our paths ever cross again, as I hope they will, I will be the first to buy you all a round at the bar.

Photo of the Team on Top of Glory Peak.

Posted by meteorologist Jim Woodmencey

Waiting for a Good Crop of Corn

2011-04-16T05:28:00.000-07:00

As blasphemous as it sounds, that’s enough powder for one season. Who isn’t ready for some warm, sunny weather, and some good corn skiing?

Corn skiing has nothing to do with making turns on a slope in Nebraska, if there even are any slopes in Nebraska? It’s about the optimal spring skiing condition. It’s about that feel of carving high-speed turns on a butt-smooth backcountry snowfield, which can be just as exhilarating as floating through thigh deep powder in January.

The term “corn snow” comes from the kernels of frozen snow grains that break loose off the surface of the snow when you apply your edges in a turn. These rounded, melt-freeze snow grains, often about the size of corn kernels (thus the name), trickle down the slope ahead of you.

The corn is best when the sun just begins to heat the top quarter-inch of the snow surface. You can carve a turn like you would on a groomed slope at a ski area. Except this condition is happening in the backcountry, on the un-skied, smooth slopes, groomed by Mother Nature. (Photo of spring skiing in Grand Teton National Park).

Weather Makes the Corn Grow

To get good crop of corn in the mountains, several things need to happen in unison. Or else, either the crop won’t grow, or it will become damaged. Sunshine is not the only weather factor corn relies on. Cloud cover and overnight temperature are also critical. Additionally, you cannot have had any recent new snow.

To really know if the weather is “growing” a good crop of corn, pay attention to the recent weather and the forecasted weather. Here’s a corn crop checklist and some explanation for each.

Corn Snow-Weather Checklist

1) No recent new snowfall.

2) A spell of warm and sunny weather.

3) Clear skies overnight, or the last two nights.

4) Below freezing temps in the morning, at all elevations in the mountains.

5) Sunny or Mostly Sunny skies during the day

Details:

1) No new snow: An inch or two of new snow will take a day or two to melt down and re-freeze. Ten inches of new snow may take 5 days to cook down to a good, solid frozen surface.

2) Warm and Sunny: First you need a stretch of warm temperatures and lots of sunshine to melt the snow, and start cooking up the corn. That’s the melt part of the melt-freeze cycle that makes a melt-freeze crust. If you don’t have wet snow on the surface during the day, it just won’t be real corn the next morning. It’ll just be a hideous suncrust. There’s a difference! (Photo of Melt Freeze Grain Cluster)

3) Clear skies overnight: You must have clear skies overnight to let the wet snow consolidate back into a frozen crust of rounded melt-freeze snow grains, all glued together. Even a thin overcast layer of high clouds can cause the snow to not re-freeze completely. This is because the clouds act like a blanket, insulating the snow and holding in the heat. Actually, what is going on is, at night the out-going radiation from the surface of the snow gets re-radiated back to the earth’s surface. As this radiation is reflected back down to earth by the cloud bases, it inhibits a solid freeze.

4) Below Freezing temps: It must get to at least 32 F or 0 C overnight at the elevations you want to ski. If not, the corn won’t last long and you’ll be punching through the crust or leaving deep ruts in the slush.

5) Sunshine during the day: Cloud cover in the daytime can also have a negative effect on the corn by not letting enough sun in to properly melt and loosen the bonds between those melt freeze snow-grains. If the sun isn’t hitting the slope, you’ll end up just skiing a frozen ocean that never softens into good corn snow.

Rule-of -thumb is: If you can’t see any stars before you go to bed, you probably don’t need to bother getting up early the next morning to ski corn.

Timing is Everything

Corn-snow farmers must rise early to hit it just right. East facing slopes will cook first, and after about 9:30 a.m. most spring mornings they are usually done. Due-south facing slopes might last until maybe 10:30 a.m. Southwest facing slopes should be ready around just before noontime.

It’s better to be there on top and have to wait for the corn to go-off, than it is to arrive too late and miss the good stuff. And then experience the embarrassment of leaving behind deep ruts in the wet snow that will take many days to heal back over to a smooth slope. After all, this is all about seeking out a smooth, untracked, snow slope to truly experience the thrill of corn skiing.

Article and ski photo by Jim Woodmencey, meteorologist

Snow grains photo from Alaska Ice & Snow Research

Will it be 8 or 9 Months of Winter?

2011-04-09T05:42:00.000-07:00

About the only question remaining for Jackson Hole is, when is winter going to quit?
In the Tetons the first significant snowstorm of the year in the mountains happened on September 10, with about a foot of snow above the 9,000-ft. elevation.
(Photo below left of Ranger Ron Johnson near Paintbrush Divide Sept. 10, 2010)

Here we are April 9th and we just finished a week (Monday thru Friday) that saw an additional 40 inches of snow fall above 9,000-ft.
(Photo below right of Chris Harder & Ray on top of Snow King, April 7, 2011)

If it keeps snowing into May in the mountains,
that'll be 9 months of winter.

In the Town of Jackson we started accumulating snow in October, and we haven't really stopped yet. That's 7 months of winter so far, will it be 8?.........read on for more about that later....

SO, HOW BIG WAS THIS WINTER?
Depending on how (and where) you measure your snowfall, the winter of 2010-2011 in Jackson Hole was big, and must be considered in the top three all-time, by almost any measure.

As of this morning (April 9, 2011) there was 155 inches of settled snow at the base of Rendezvous Bowl at JHMR (that's almost 13 feet deep!). That matches the biggest year for settled snowpack depth on this date, set back in April 1997. (See Table below).

As far as snowfall from October 1 thru April 8, the Winter's of 1996-97 and 2007-2008 both had more snow than this past winter. Numbers from last winter are thrown in for comparison also.

Snow Comparison At Rendezvous Bowl (9500-ft.) JHMR
Winter thru April 8th	Total Snow Depth (in.)	Total Snowfall (in.)
1996-97	155	585
2007-08	134	572
2010-11	155	570
2009-10	88	404

We are darn close to that magical "600" inches of snowfall for the winter at JHMR. The Raymer Plot read 599 inches this morning. Same date in 2008, it stood at 609 inches.
Why is 600 inches so "magical". Because that's 50-FEET of snowfall!

LA NINA
The buzzword this winter was "La Nina", which began last fall and remained strong through January or February before it showed any signs of weakening. La Nina of course usually means more snow for the Pacific Northwest and Northern Rockies, and that played out in spades this winter.

What's most unusual about this La Nina is, that it affected areas further south, like the Sierra's in California and the Wasatch in Utah, and even the central Colorado Rockies did O.K. and had well above normal snowfall winter's also.

The La Nina is a little weaker now, although we are still feeling her impacts, and she is expected to continue to weaken into June, when we should get back to more normal climatic conditions.
NOTE: That does not mean it is going to snow until June!

You can get all the La Nina, El Nino, & Long Range Forecast info you want by scrolling down the NWS Discussions & Outlooks Page of www.mountainweather.com

Weather Rap for the First of April.....no foolin'

2011-04-01T09:23:00.000-07:00

A warm Ridge of High pressure that has been building inland over the western U.S. the last 24-hours will get flattened out by a Trof of Low pressure that will be moving across the Northwestern U.S. the next 24-hours.

Very HOT in the Southwestern U.S. on the last day of March 2011......75 in Moab, 79 in Zion, 92 in L.A., 101 in Palm Springs, and hottest was 103 in Death Valley.

Still some clouds coming over the top of that Ridge in a WNW flow over us today, which may cause a few showers over Yellowstone Park and the Teton Mountains, otherwise, just some clouds moving by from time to time today. And warm spring-like temps.

That weather system coming into the Pacific Northwest will bring Jackson Hole some rain on Saturday, by afternoon. A strong cold front will then move through sometime Saturday evening and that will change the rain over to snow at all elevations. Expect dramatically cooler temps by Sunday.

That Low pressure center moves by to the north of us and out into the Dakotas on Sunday. Some moisture remains behind this system in a North to NW flow Sunday & Monday for some light snow.

It now looks like a somewhat moist Westerly flow will be over us Tuesday & Wednesday, with warming temperatures bringing a chance of some valley rain showers and some snow in the mountains.

Text provided by Meteorologist Jim Woodmencey

Graphics by IPS MeteoStar LEADS On-Line

Flow Across the Pacific

2011-03-26T07:55:00.000-07:00

There's some good news, and some bad news, and some good news again.... about the flow across the Pacific over the next 5 to 7 days.

The first good news is, a Low pressure system this weekend will bring snow Saturday night and Sunday to Jackson Hole.

The bad news is, as we go into the middle and end of next week it looks like a Ridge of High pressure will build over the Western U.S. and Rockies and send storm systems that are lined up out in the Pacific right now to the north of us into Canada and SE Alaska.

The good news about that is..... any radiation that might be in that flow coming across the Pacific from Japan will also get diverted well to the north of Jackson Hole.

Text by Meteorologist Jim Woodmencey
Graphics by IPS MeteoStar, LEADS -OnLine

Nuclear Spring

2011-03-18T07:27:00.000-07:00

Concern about radiation particles being carried across the Pacific and into the western U.S. from Japan has become a popular topic.

Despite assurances that radiation amounts will be very low by the time any of that makes it to the West Coast, the flow in the upper levels of the atmosphere is setting up to bring whatever is being emitted over Japan during the course of the next week, directly towards the West Coast.

In the short term, most of the radiation that is already in the atmosphere will be carried over the Aleutian Islands of western Alaska. The rest of Alaska should be missed, as the flow abruptly turns to the southeast across the Gulf of Alaska and gets involved in the Low pressure center that is sitting just off the West Coast.

Top map shows the jet stream position (at 300mb or ~ 30,000-ft.) on Saturday morning March 19.
The middle map shows the wind speeds and flow at 700mb ~ 10,000-ft., which is more representative of the level at which any radiation in the atmosphere would fall out with precipitation.

Strongest winds point at the far western tip of Aleutians, then turn southeast and decrease considerably before turning eastward into the southern half of California.

The bottom map shows the forecasted jet stream position position by the end of next week, which may be more of a concern as the flow straightens out into more of a direct pipeline from west to east across the Pacific.

Not surprisingly, skiers have already inquired about what this radiation might mean for our weather as we go into Spring. "Does it mean more snow or less snow? Or, will it melt the snow that is already on the ground?"

I don't really know much about the effects of radiation particles in the atmosphere. They are not like volcanic eruptions and their particles, which can actually enhance snowfall by adding more ice nuclei to the atmosphere. It is my understanding that radiation particles attach to dust particles that already exist in the air, and then fallout with precipitation, along with the dust particles.

Even if a nuclear cloud did enhance snowfall, would you really want to rush out and ski that?

Technically, it wouldn't create a Nuclear Winter, since Spring begins Sunday, March 20, 2011 at 5:30 p.m.

A Nuclear Spring, maybe.

Text by Jim Woodmencey, meteorologist
Graphics from IPS Meteostar, LEADS On-Line

Snowfall and Snowdepths, so far…

2011-03-14T09:13:00.001-07:00

Comparing snowfall totals this winter to last winter, through early March around the Jackson Hole area, shows that we have had about 7 more feet of snowfall this winter than we did last winter up at around the 9500-ft. elevation.

Total snowfall for the season so far at the bottom of Rendezvous Bowl at JHMR stands at 416 inches as of Monday March 14, 2011. Same date last March the total snowfall was 332 inches. A difference of 84 inches, or 7 feet.

Settled snow depths are a solid 4 feet deeper this winter in the mountains than this time last winter, almost 10 feet deep this year vs. barely 6 feet deep at 9500-ft. last year.

Even in the valley, we are ahead of last year by a good margin, with around 3 ½ feet at the base of Teton Village this year, while last year we had just under 2 feet on the ground. Total snowfall at the base of Teton Village this year is up to 158 inches, while last year we had only 101 inches of snowfall. Almost a 4 foot differential.

Even with all the snowfall we’ve had, the Snow Water Equivalents in the Snake River Basin are holding steady at around 110% of normal. Philips Bench Snotel, the closest to Jackson (located on the east side of Teton Pass at an elevation of 8200-ft.) is currently sitting at 103% of normal.

So, I suppose after two relatively dry winters in a row, this one seems much wetter, or snowier, when in fact it is closer to what we might consider “normal”.