Thursday, November 22, 2012

The Jet Stream Dictates our Weather

It's Thanksgiving, and technically Winter is still a month away. And the weather pattern that would bring winter on in full is still not quite there yet for the Rockies. Lots of snow the last few days in the Cascades, where cold air and the jet stream have been hanging out. And a  little new snow in Jackson Hole this morning from the storm passing through last night.  Looks like one more shot of snow this weekend, again starting warmer on Saturday and cooling Sunday into Monday, will also help kick off the ski season.

However, the split jet stream that has been over the Western U.S. needs to go away, and the main Polar Jet stream that carries both Pacific moisture and cold air from the Gulf of Alaska need to dip a little further south. It dipped over us last night, but will stay north of Wyoming Friday & Saturday.

We do see the jet dip south again over the weekend, but then by the middle of next week it looks like it will head back to the north of us.  Therefore, we may have to wait a bit longer for that jet to straighten out and get us fully into a winter storm cycle.
(See maps of current jet, forecast jet late Sunday & forecast jet next Thursday).

Thanksgiving Day

Sunday Night, Nov. 25th

Next Thursday Nov. 29th

General Weather Rule of Thumb: When the core of the jet stream is north of us, we get warmer and drier weather. When the jet is right over us, we may get Pacific moisture, but temps may be too warm and we get rain at lower elevations. When the jet is just to the south of us, that is usually when we get our best snowfall.

I'll keep an eye out for changes and update the long range outlook for you in the next blog post.

Text by meteorologist Jim Woodmencey
Maps from NCAR

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