textproduct: Western and Central Wyoming

KEY MESSAGES

- A storm system will bring scattered to widespread rain and snow to the area tonight through Friday. The heaviest snow will be across the Bighorn Mountains tonight and Friday.

- Light to moderate snow is expected across most lower elevations tonight and Friday. Northern Johnson County is most favored to see up to six inches of snow Friday morning along with gusty northwest winds.

- Strong winds of 30 to 45 mph will be seen across the area Friday.

- Overnight low temperatures will drop into the 20s and low 30s tonight and Friday night. Abnormal early season vegetation will be especially susceptible to this cold.

- A warming and drying trend begins Saturday across Wyoming and continues through the middle of next week, with more active weather expected by the end of the week.

UPDATE

Issued at 1238 PM MDT Thu Apr 2 2026

The large downstream difluent region ahead of the deep upper- level low continues to impact Wyoming today. The western WY mountains have seen 4 to 10 inches of snow; southwest WY has had thundersnow; and the NWS office in Riverton even had a brief rain shower this morning (the first precipitation in over 15 days but still a trace). Based on the latest forecast guidance, especially with high-res CAMs, have gone ahead and added a Winter Storm Warning to northern Johnson County, due to marginal snow amounts around 6 inches, but accompanied by 30 to 40 mph gusts for several hours early Friday morning. Should be quite an impact to I-90 and the Buffalo area. Have also added some Winter Weather Advisories due to the higher confidence of some areas seeing 3-5 inches of snow, especially as the core of the upper-level low traverses north-central WY on Friday. This includes the eastern portions of Big Horn and Washakie counties where storm dynamics and upslope flow should produce some much- anticipated precipitation and snow from Shell to Ten Sleep to Big Trails, and even to the west toward the Bighorn River. Advisories were also issued for SE Johnson County, lower elevations of Natrona County, and Casper Mountain. Again, favorable moisture convergence with the cold air and gusty NNW winds should bring 3-5 inches of snow to some locations, and 6 to 8 inches of snow on Casper Mountain. Left all other hazards in place for the storm duration.

Honestly wish the 500 mb low center was about 100-150 miles to the south. Then, Wyoming would be seeing a much more widespread precipitation producer. But this storm is bringing some much needed water to the area, along with cooler temperatures to dampen the fire weather conditions that were seen in March. Hopefully, the SNOTEL stations will see and increase of percent of median snow water equivalent as a result. The pattern though becomes warmer and drier starting Saturday with light showers returning to NW WY late Tuesday.

DISCUSSION

Issued at 404 AM MDT Thu Apr 2 2026

The active start to April continues as the leading wave ahead of an approaching low pressure system pushes into Wyoming. This will be most focused on western Wyoming through the morning hours as moisture streams up the Snake River Plain ahead of an advancing cold front. Snowfall rates will be heaviest during this time for the Tetons, Salt/Wyoming Range, and the western Wind River Range as southwesterly low-level flow is maximized, bolstered by a 100+ knot upper level jet. Elsewhere west of the Divide will see a mix of rain and snow depending on elevation. Jackson Hole and Star Valley are most likely to see more persistent snowfall, and we have added a Winter Weather Advisory to account for any snow this morning and more to come later today and tonight. One other area that has potential for snow through the morning and early afternoon is southern Lincoln County where some high resolution models have pinpointed up to a few inches; confidence is not high enough to issue any highlights for now but certainly something to watch.

The low and attendant cold front will begin to progress east over the area after 18Z. While this will mark an overall decrease in available moisture for western mountain snow, precipitation chances will increase everywhere else as synoptic lift ramps up. This will fall predominantly as rain through the afternoon as temperatures remain warm, especially east of the Divide. Wind will also be a factor today as the surface pressure gradient increases in magnitude ahead of the front; southwesterly gusts of 40 to 50 mph will be widespread through the afternoon.

By midnight tonight the low should be centered over the middle of Wyoming. This will mark the beginning of the next phase of this event as moisture is wrapped cyclonically back into the area from the north. Precipitation will accordingly be most focused east of the Divide Friday as an upsloping component is established. Still, enough moisture will return to western Wyoming for another round of moderate snowfall there, and we'll keep the winter highlights going through Friday afternoon. With colder temperatures behind the front, snow will fall east of the Divide even at lower elevations tonight. The Bighorns will be most favored for heavy snow given this setup, especially the northern half of the range. While accumulations across lower elevations will mostly remain on the lighter side (an inch or less), there will be some favored locations that may soon need winter highlights issued. The most likely spot will be northern Johnson County as upslope flow is maximized there Friday morning. This could bring a quick few inches before noon (40 to 60 percent chance of at least 3 inches), and with a strong northerly wind may lead to travel impacts along the I-90 corridor. While confidence is lower, other areas that could see 2 to 3 inches of snow tonight through Friday will be the eastern Bighorn Basin and the Casper area.

Precipitation will wane Friday evening as the low pulls away from the area. Clearing skies should lead to a colder Saturday morning. However, temperatures will warm up quickly as ridging builds back in over the region. This will lead to a warm and dry weekend with temperatures peaking into the 50s and 60s across the valleys and basins. Looking ahead, ensemble guidance favors the warm and dry trend to continue before chances increase for the arrival of the next system midweek.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 412 PM MDT Thu Apr 2 2026

Impactful aviation weather is forecast over the next 24 hours, with widespread MVFR to IFR conditions due to periods of snow, along with breezy winds gusting 20 to 30 kt. Plan on widespread mountain obscurations. Hit-or-miss showers will continue this afternoon and evening, moving roughly from southwest to northeast across the region. Snow levels decrease this evening, so rain showers will be become snow showers by sunset. The core of the incoming weather system remains on track to bring several hours of more persistent snow to western Wyoming valleys this evening, between 03/0100Z and 03/0500Z, including at sites such as KJAC.

After 03/0500Z, snow (moderate to heavy at times) will develop over northern Wyoming basins, including for locations like KGEY, KBYG, and KWRL. Winds will shift from westerly to northerly for locations east of the Continental Divide as snow moves in, with gusts 30 to 40 kt accompanying the cold front. This snow will continue well into the morning hours, tapering off for most around 03/1800Z. However, light precipitation lingers longer for locations in central Wyoming, such as KCPR, as persistent light upslope flow remains until around sunset Friday.

RIW WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning until 6 PM MDT Friday for WYZ001-008-009- 012-014-015-024.

Winter Weather Advisory until 6 PM MDT Friday for WYZ002-013- 023.

Winter Weather Advisory from 11 PM this evening to noon MDT Friday for WYZ004-006.

Winter Storm Warning from 1 AM to 6 PM MDT Friday for WYZ010.

Winter Weather Advisory from 6 AM to 6 PM MDT Friday for WYZ011-020-022.