textproduct: Western and Central Wyoming

KEY MESSAGES

- Rain and snow will end this morning, with increasing sunshine through the afternoon.

- Mild and dry Wednesday, with elevated fire weather from Muddy Gap through Natrona County.

- The next weather system has good potential to bring accumulating snow to much of the area Thursday and Friday.

DISCUSSION

Issued at 242 AM MST Tue Mar 3 2026

It is often said that sports are a matter of inches, with games being decided by a very small margin. That remains me of the forecast I made last night for rainfall amounts in central Wyoming, but in a matter of a small number of miles versus inches. It called for a quarter to a half an inch of rain in places like Casper and Riverton. Well, that has not materialized with only light rain and very light amounts. However, just go to 25 miles to the south and Lander has around a quarter of an inch or rain and it is still raining as of 2 am. I have to eat a little crow on this.

As expected, the heaviest is across southern Wyoming. The area of low pressure shows up across southwestern Wyoming, working its way slowly to the east near the Wyoming / Colorado line. There is some decent snow falling in Lincoln County at this time with some enhancement by the left front quadrant of a jet streak, a bit more than I thought last night. We will go ahead and issue a short term Winter Weather Advisory for snow. Of more concern is Sweetwater County, including Interstate 80. The HREF ensemble is showing a greater than 1 in 2 chance of 3 inches to east of Rock Springs. Amounts are borderline, but for impacts, especially to Interstate 80, we will again issue a Winter Weather Advisory. Elsewhere, rain and snow should end from north to south and be basically over by around noon with increasing amounts of sunshine following that. Temperatures will remain mild in areas with no snow, again averaging well above normal.

Wednesday looks like a quiet day as well, for the most part. The one concern is from Muddy Gap through Casper where a gusty wind will develop ahead of the next system moving in from the west. As for fire weather highlights, we will definitely have the wind with some gusts to 40 mph possible. The question is humidity. As of now, HREF ensemble guidance is only giving less than a 1 out of 2 chance of relative humidity falling below 20 percent, with only a 1 out of 10 chance below 15 percent. So, we will hold off on any fire weather highlights for now. If conditions worsen, the day shift can issue a watch and we can upgrade if needed tomorrow night.

Then we look toward what looks to be the main story for the rest of the week. This is in the form of another Pacific system that will approach from the west. At this point, this one looks to have a good setup for a decent snow across much of the area. There will be lee cyclogenesis occurring Colorado, turning flow more easterly then northerly, bringing in moisture and then good north to northeasterly upslope flow. The 700 millibar low may be tracking across the Wyoming-Colorado border, a good location for a decent storm. Details are still highly uncertain in regards to placement of timing of heaviest precipitation though, as the GFS and European have performed a Freaky Friday swap and are polar opposites of what they showed yesterday. A few things I am fairly confident on. One is that the timing in the current forecast is the fastest the precipitation would move into western Wyoming. Personally, I think all areas will stay largely dry through midnight with only light precipitation through late Wednesday night. Even most of Thursday should stay dry East of the Divide, with the bulk of the precipitation holding off until after sunset. It will also start warm, so the precipitation may begin as rain before changing to snow, in most areas by midnight Thursday night and all locations by sunrise Friday and then possibly continuing through the day. As for a first guess at amounts, most ensemble guidance gives at least a 2 out of 3 chance of 3 inches or more for most of the area, with at least a 1 in 2 chance of 6 inches or more in the favored northerly upslope areas like Thermopolis, Lander and Casper. We will almost certainly need some highlights for this storm but it is too early at this time. Following this, high pressure should bring dry weather for the weekend. Temperatures may be lower than what is in the forecast given the fresh snow cover, but with the Pacific origin of the air, it will not be bitterly cold. This, combined with the strong March sun, should begin melting the snow over the weekend.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 414 AM MST Tue Mar 3 2026

Precipitation remains limited to KRKS this morning, with low clouds, fog, and snow continuing there through about midmorning. Remaining sites have all shifted to VFR as skies have quickly begun to clear. Expect VFR at all sites by 18Z, and continuing at all sites through the next 24 hours.

RIW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 8 AM MST this morning for WYZ027.

Winter Weather Advisory until 11 AM MST this morning for WYZ028>030.