UPDATED (5:00 AM 11/30): Significant Winter Storm Today/Tonight

A complex weather system currently moving into Idaho will track across the Cowboy State today and Thursday. Snow has begun to fall across northwest Wyoming this morning and will spread southeast across the rest of the state this afternoon and evening. Precipitation may begin as rain or a rain/snow mix, but will transition to snow everywhere by this evening. Windy conditions will develop east of the Divide this evening and overnight, producing areas of blowing snow and hazardous travel conditions.

IMPORTANT NOTE: Due to the complexity of this system a fair amount of uncertainty remains in exactly how much and where snow will fall across the Cowboy State. That said, the confidence in the forecast of gusty winds and bitterly cold temperatures is high. These two factors will combine with the snow that does fall to create hazardous travel conditions across the state, including the I-90 and I-80 corridors.

 

The above animation runs from 11 PM Monday through 5 PM Thursday in 6 hour steps.

It shows the track of the upper level trough of low pressure and cut-off low (white contours) that will impact Wyoming Wednesday and Thursday. The colors indicate relative temperatures. Note the cold Canadian air moving into the area Thursday.

A strong surface high building in behind the system will increase the pressure gradient across the region and cause extensive areas of blowing snow in addition to the expected falling snow.

 

The animation above runs from 11 AM Wednesday through 5 PM Thursday in 6 hour steps.

It shows the area of surface high pressure (white contours) moving south out of Montana into Wyoming. This high pressure combines with an area of low pressure to the south to create a very stong pressure gradient across the state. This strong pressure gradient results in very strong winds (shown in colors) across portions of Wyoming, most notably across Sweetwater County and the I-80 corridor.

This system will bring the largest impacts to areas east of the Divide. Some specific areas that may see significant impacts include:

  • The northern Bighorns and Johnson County.
  • The northern Big Horn Basin
  • Sweetwater County and the I-80 Corridor
  • Rattlesnake Range and Green Mountains (including Jeffrey City)
  • The southern Wind River Range (including South Pass)

These areas may see areas of blowing and drifting snow and could even have white-out conditions at times Wednesday night into Thursday morning. Highlights (Warnings/Watches/Advisories) have been issued for these areas. As mentioned before there is a fair amount of uncertainty in the snowfall forecast with this system and other areas such as the Lander Foothills, Casper, Casper Mountain, and the Cody Foothills will need to be watched.

Let's take a look at the current (as of 5 AM Wednesday) storm total snowfall forecast (5 AM Wed - 5 PM Thu):

The image above depicts the expected storm total snow accumulation. Click on the picture above for a larger image.

To add insult to injury, very cold air will filter in behind the system so expect temperatures to take a nose-dive late this week and through the weekend, with Friday morning being the coldest time. Keep an eye on our homepage for the latest forecasts, check out the Area Forecast Discussion for more analysis from a forecaster, and please "like" us on Facebook to share pictures and reports with us during the storm. Also, here is the latest Special Weather Statement about the storm. Continue to stay tuned for more detail in future Watches, Warnings, and Advisories on the timing and severity of expected conditions near you. To keep track of current road conditions across Wyoming call 5-1-1 or go to wyoroad.info.



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