textproduct: Western and Central Wyoming

KEY MESSAGES

- Virga showers, moving to the southeast, will end through the evening. A brief gust up to 40 mph will remain possible from these passing showers.

- The next weather system moves across the state Monday and Tuesday, bringing a better opportunity for rain and snow. Confidence remains low in rainfall and snowfall amounts.

- Freeze Watches now in effect for lower elevations east of the Continental Divide Tuesday night into Wednesday morning.

UPDATE

Issued at 144 PM MDT Sun May 3 2026

Isolated storms have been developing along the eastern slopes of the Bighorn Mountains and sliding southeast through Johnson County this morning and into this afternoon. This will continue through the afternoon hours, with more isolated storms and scattered showers developing across northern portions of the area this afternoon. Widespread scattered virga showers will develop across the area this afternoon as well, with gusty downdraft wind associated with them. Gusts could be as high as 50 mph due to large temperature/dewpoint spreads this afternoon. The dry conditions, combined with gusty downdrafts, will lead to continued elevated fire weather conditions today. Moisture moves in tomorrow, which will lead to an improvement in fire weather conditions. Forecast remains on track for a cold front to push through Monday into Monday night, with scattered rain showers and thunderstorms focused from central to southern portions of the area. Model guidance keeps decreasing QPF amounts little by little, but where storms set up will still receive around 0.5" and up to 1" of rain. Of note for Tuesday afternoon is the potential for some stronger storms across southwest WY. Freeze Watches have been issued for Tuesday night into Wednesday morning for lower elevations east of the Continental Divide, with widespread low temperatures of 20-30 F.

DISCUSSION

Issued at 211 AM MDT Sun May 3 2026

The more progressive pattern continues across the northern Rockies during the next week. Today will start with some high clouds and warm temperatures reaching the 60s and 70s. The approach of the next weather system will bring enough instability today for some shower activity along the higher reaches of the Absarokas and Bighorns. While moisture has started to increase across northern WY in the past 24 hours, there still isn't a whole lot to produce much accumulation with showers today.

The main system itself will begin to impact Wyoming Monday morning, as a front sweeps in from the north. The first push should reach the northern WY/MT border right around sunrise Monday, and reaches around the Continental Divide by 18Z, before spreading southwest late in the afternoon. The front will bring along valley rain and mountain snow behind it, spreading southward through the day. Most areas should receive a good wetting rain, but some shadowing across the Bighorn Basin may keep amounts there to a minimum. With the front stretched along the southern WY border during the evening, best opportunity for rainfall would be focused from the Winds east along the Greens and Casper Mountain. Rain decreases late Monday night into Tuesday, but a brief secondary north wind push will keep very light rain/snow going for all except for the Bighorn Basin and the NW Parks during the day Tuesday. Current accumulation numbers have remained steady for a couple tenths for the southern 2/3 of the state, with the highest band near a half inch for the Winds east to Casper Mountain. Models have nudged amounts downward slightly since yesterday, and with the last couple events the models have overestimated final totals, so current totals may be a bit high.

Once this system sweeps southeast early Wednesday, upper level pattern remains from the northwest, so while temperatures will return to the 60s and 70s, weak embedded impulses may bring light heating-of-the-day showers to the northern mountains through the rest of the week.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 351 PM MDT Sun May 3 2026

Gusty afternoon winds decrease this evening. A cold front then moves in from the north starting around 12z. The main impacts will be to sites east of the Divide, with a gusty north wind shift and increasing clouds. KCOD could see a period of MVFR clouds after frontal passage. Precipitation chances also increase after the front, and increase further with daytime heating late Monday morning and through Monday afternoon. Have kept mostly PROB30 groups for now given the expected scattered nature of the showers and storms, though could see prevailing groups for a few hours as timings become more clear with future updates and better hi-res data. Main threat with any showers/storms Monday is gusty outflow winds.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

Freeze Watch from late Tuesday night through Wednesday morning for WYZ003>006-010-011-017-018-020.