Wednesday, March 5, 2014

A Rare "Thundersnow" Event in Jackson Hole

Meteorologist Jim Woodmencey
There was a "Thundersnow" event that occurred over the Jackson Hole area Tuesday evening, March 4th, 2014.  A small, but very potent upper level disturbance passed through, concentrating a brief but intense period of snowfall right over Teton County Idaho & Teton County Wyoming between 5:00 and 8:00 pm MST.

Thundersnow is a rare occurrence, but basically it is a summer-like thunderstorm with winter-like snow in it, and yes, there was lightning in it. In 2 or 3 hours this storm produce between 3 and 5 inches of snow around Jackson Hole and the Teton Mountains.

To produce a thundersnow-storm,  a very unstable atmosphere is required, we had that as temps in the valleys were up around 40 degrees or warmer Tuesday afternoon, and the much colder air aloft associated with that Trof created the needed instability in the atmosphere. The timing of the clashing of the warmer air down low and the colder air aloft could not have been better. And, there was a nice impulse of moisture to go with it.

In this case, in order to generate lightning in the winter months, the mountains provided the extra lift required to develop that thunderstorm last evening. As the cell dispensed it's precip, temperatures
in the valley dropped to 30-degrees almost instantly.
 
Lightning Map below, with satellite & radar images from around the time of greatest intensity.


Lightning Strike Map from Tuesday evening



Infra-red Satellite Image
Base Relectivity Radar Image

You can see how small this thundersnow cell was, relatively speaking. Because of its size, it is one of those weather events that is difficult to forecast for, at least very far in advance. There was virtually no indication that this storm would blossom like it did, until about an hour ahead of time. Small features like this totally slips through the cracks in the computer models.

There was very little indication on anything I looked at early on Tuesday morning to suggest there would even still be any precipitation by evening Tuesday.


Post by Jim Woodmencey, meteorologist
Lightning Map & Radar graphic from Leads On-line
and Satellite image from NOAA

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