textproduct: Western and Central Wyoming

KEY MESSAGES

- Isolated showers and/or virga and a few rumbles of thunder are possible (20% to 40%) this afternoon across much of the area, especially over higher terrain and northwestern Yellowstone. Gusty outflows 35 of 50 mph are possible with showers/virga.

- Temperatures warm into the 70s and 80s each afternoon this week, with highs approaching 90s by Saturday. Isolated afternoon shower and thunderstorm chances on Thursday across northern Wyoming.

- Widespread elevated fire weather conditions are expected each day due to low relative humidity values around 10 to 15 percent.

UPDATE

Issued at 1144 AM MDT Mon Jun 1 2026

The weak disturbance, embedded within southwest flow aloft, will continue to traverse over the state this afternoon. For most, the only indication of the passing disturbance will be scattered clouds given unsaturated low levels and breezy winds. However, there is generally a 20% to 40% chance of virga and/or a light rain shower and a few rumbles of thunder through 8PM across the area. HiRes model guidance is hinting in a few "bands" of virga and/or light rain showers that are likely co-located with vorticity maxima and where orographic lift is enhanced. These "bands" are forecast to be over northwestern Yellowstone National Park, the northern Salt River and Wyoming Ranges to the southern Absarokas, and from the Unita Mountains to Casper area. The greatest chances (up to 40%) of light rain making it to the ground is across northwest Yellowstone due to proximity to the upper low and increased moisture. Dewpoint depressions this afternoon are forecast to be 35 to 50 degrees Fahrenheit, so gusty 35 to 50 mph winds are possible with any virga or light showers. A few rumbles of thunder are possible as well with lifted index values between -1 and -3C.

Elevated fire weather conditions are expected each afternoon this week given the warm temperatures, low relative humidity values around 10 to 15 percent, and breezy winds.

DISCUSSION

Issued at 211 AM MDT Mon Jun 1 2026

The first lobe of the trough spinning across the NW US has shifted northward into Montana, taking along with it the showers from yesterday. Another shortwave rotates through during the day today, getting pulled northward into yesterday's wave. This wave is already noted on local radars as high based showers/virga moving into far SW WY this morning. Moisture will be notably lower closer to the surface across the region, with the only areas where humidity remains above 25% would be the highest elevations of the NW mountain ranges. This combined with today's wave being weaker than yesterday's will limit actual accumulation chances to 20% or less, again focused exclusively on the higher elevations.

Tuesday bears some more watching as short-range models have been hinting at some thunderstorm activity with another weak wave shifting through the state. The wave isn't all that notable, but a more defined moisture boundary across central WY may become the focus for thunderstorms for greater Natrona and Johnson Counties during the afternoon. With temperatures jumping into the low to mid 80s, the strength of any capping inversion would be the main factor on where thunderstorms would initially fire before shifting into eastern WY. Right now the placement of these features is not conducive at the same time for convection for central WY, but any adjustments on timing may need an increase of PoPs during the afternoon.

Wednesday sees weak ridging shift into western WY, settling convection down for the day, and bringing temps back into the 70s and 80s. Another wave sweeping by across Montana brings another chance for showers and thunderstorms across the northern half of the state, before ridging return for late week into the weekend.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1110 AM MDT Mon Jun 1 2026

VFR conditions prevail through the period. Some very light showers, or more likely virga showers, will be around this afternoon, mainly over and around mountains. These showers could produce brief outflow gusts up to about 40 knots. Any gusty winds this afternoon decrease this evening following diurnal trends.

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

None.