The advertised pattern change is underway as the storm track which has bypassed Star Valley much of December will be providing a snowy end to the year. As can be seen on this evenings water vapor imagery a moist westerly jet is moving eastward across the eastern Pacific toward the Pacific Northwest.
|Water Vapor Imagery Monday Evening 12/26/2011|
The effects will be noticed beginning with increasing cloud cover holding temperatures well above the zero readings experienced much of the nights this month in Star Valley. Precipitation in the form of snow will commence during the daylight hours Wednesday It appears that intensities will pick up by Wednesday night and continue through Thursday and possibly Friday. Temperatures will warm to near and possibly slightly above freezing in Star Valley by Thursday. While precipitation will likely remain as snow, the warmer air mass should lead to a much wetter snow than that experienced so far this month. The Riverton Weather Forecast Office has indicated over a foot can be expected in the nearby mountains and possibly 6-12 inches in Star Valley with the heaviest amounts from Thayne to Alpine.
|Snowfall forecast 12/28-29 2011|
With the strong westerly winds, the snow will fall mainly over and west of the mountains of Western Wyoming. Downslope flow will result in little snow over much of central and eastern portions of the state, however winds will be strong and gusty.
The greatest amounts are likely over and west of the Tetons where by this weekend, new snowfall could be measured in feet, possibly up to 2-3.
The month long stretch of below freezing days could come to an end at Thayne E.S. during the next couple of days.