While there has been at least a trace of snow observed at Star Valley Ranch for the past 10 days it has resulted in just 12 inches. Almost half(5 inches) fell last Sunday morning. There are signs that the storm track, which has been bypassing Star Valley much of February, will be more of a player in our weather for the remainder of the month.
A weak upper trough passing through the area will result in a couple inches of new snow today(Friday). This should be a rather low moisture content snow with snow to liquid ratios around 20:1. That is, if 20 inches of snow fell and that snow was melted, it would produce 1 inch of liquid precipitation. A wet snow would have ratios of 10:1 or less.
Examining the morning upper air analysis shows the weak system resulting in today’s snow at 700mb(10,000 ft) tracking across the northern Rockies:
|700 mb Analysis Friday Morning Feb 17 2012|
While today’s snow is rather obscure on the water vapor imagery this morning, a much more powerful storm is approaching the Pacific Northwest coast.
|Water Vapor Imagery Friday AM February 17, 2012|
There are still signs that the storm moving onto the Northwest coast later today will weaken as the energy again tries to split. Unlike recent systems, Star Valley and western Wyoming and southeastern Idaho should receive a period of significant snow as the upper trough passes this weekend.
With the current weak system passing on to the east the associated snow is expected to generally end by this evening.
Looking ahead by late Saturday afternoon, snow will return to the area as the storm now moving toward the Pacific Northwest, although having weakened, will be crossing the Idaho/Western Montana /Western Wyoming region.
|700 mb Forecast Saturday evening Feb 18 2012|
Below is an experimental forecast for the model snowfall over about the next 3 days. Basically, displayed are various model solutions for the same forecast period. By varying initial conditions of several different models, a total of about 16 different solutions of total snowfall are made for the Star Valley area. While the range of forecast snow is from just a couple inches to nearly a foot, the mean of all models is for around 6 inches. Probably of greatest importance is that all the solutions agree that the bulk of the snow will fall beginning late Saturday through Sunday evening.
For additional technical information as well as access to other model forecast fields and locations check out this link:
Greg Carbin the Warning Coordination Meteorologist at the Storm Prediction Center has developed the SREF Display and is looking for feedback.
|SREF Forecast Total Snowfall from Friday morning until Monday evening Feb 17-20 2012 for Star Valley|
Forecast snowfall amounts depend on several factors including snow to liquid ratios, accuracy of model solutions and location relative to terrain influences. Here in Star Valley all these play important roles. Thus, a forecast of how much snow is going to fall is one of the more difficult weather parameters to make.
Given these caveats it does appear that over the weekend, several inches of new snow are likely with the possibility of the most favored valley locations receiving from 4-6 inches along the west slopes of the Salt Range such as Smoot, Turnerville, Bedford and Star Valley Ranch. It does appear that higher elevations in the Tetons and Salt/Wyoming Ranges could get over a foot.