SNOW ON THE WAY

The first significant fall precipitation event across Star Valley occurred on Tuesday. It provided  amounts ranging from 1/4 to over 1/2 inch.  Here are some observed totals.

2 NW of Etna       .80
Afton                   .58
Smoot                  .49
Thayne ES           .36
Alpine                  .32
Etna ES                .30
Star Valley Ranch  .22

Below is a precipitation map covering the surrounding regions from the recent storm

Over an inch occurred in the mountains north of Star Valley, particularly the Tetons.

For much of the event the snow level was above about 8500 feet.

A cam photo taken Wednesday afternoon shows the fresh snow on the Tetons.

The computer models have been quite erratic in forecasting what now appears to be a major pattern change coming this weekend.  However the Wednesday evening model solutions are generally agreeing that the large upper ridge now over the western states will be replaced be a strong and cold upper low pressure trough forming this weekend off the West Coast and then slowly moving eastward toward Star Valley next week.

Here is the 500 mb chart observed this Wednesday evening showing the deep low over the Central states and high pressure along the West Coast.

500MB Analysis Wednesday evening 10/17/12

Following are the forecasted 500MB charts for both this Saturday evening and Monday evening.

 The deep central states trough moves east with the upper ridge currently near the West Coast shifting all the way east to the eastern states by Monday.  The deepening trough of low pressure develops near the West Coast this coming weekend will provide an intensifying southwesterly jet across Wyoming.  This pattern would favor initially precipitation developing by Sunday over Star Valley which should mostly be rain in the lower elevations but possibly significant snow in the Salt and Wyoming ranges.

However, possibly as early as Monday morning, colder air will likely lower the snow level to the valley floor.  Additional periods of precipitation will likely occur well into next week with snow likely in the valley.

The following are the 24 hour forecasted precipitation  amounts for Sunday and Monday.

Sunday forecasted precipitation

5 day total forecasted precipitation through Monday evening

 It is still too early to be specific as to when/where and how much snow will fall in the valley; it appears that potentially 1-2 feet could occur in the higher mountains beginning Sunday into early next week.

Since a big pattern change is imminent, it is instructive to put into perspective the difficulty that the current computer models have in forecasting this type of change.  An excellent blog was posted this morning on this very subject and if interested can be seen here.

http://wasatchweatherweenies.blogspot.com/2012/10/rolling-dice-with-ensembles.html