textproduct: Western and Central Wyoming

KEY MESSAGES

- Another active weather day is in store today with most locations having a 30% to 50% chance of showers and thunderstorms. Showers or thunderstorms will be capable of 45 to 60 mph winds, heavy rainfall, and frequent lightning.

- Shower and thunderstorms chances exist each afternoon Tuesday through the upcoming weekend. High temperatures each day this week are forecast to be in the 70s and 80s with lows in the 40s and 50s.

DISCUSSION

Issued at 241 AM MDT Mon Aug 24 2026

2:30 AM upper level water vapor imagery shows largely zonal flow with an embedded shortwave disturbance over Wyoming, thanks to an upper high centered over New Mexico. This disturbance has been the focus for showers and a few thunderstorms across southern Wyoming late Sunday night/early Monday morning. As this shortwave progresses eastward through sunrise, coverage is expected to diminish with only a few isolated showers across Sweetwater County. Temperatures today, and most of this week, are forecast to have highs in the 70s and 80s and lows in the 40s and 50s.

An active day is in store as another shortwave rounds the stagnant upper high to our south. This shortwave looks to shift into western Wyoming around noon/1PM Monday, allowing convection to take advantage of peak heating (BL CAPE ranging from 500 to 1000 J/kg). Most locations have a 20% to 50% chance of a shower or thunderstorm this afternoon and evening due to abundant available moisture in the mid levels of the atmosphere. Model forecast soundings are showing a classic inverted-V profile and indicating DCAPE values around 1100 J/kg. Additionally, dew point depressions range from 45 to 55 degrees. These parameters suggest that thunderstorms will be capable of 45 to 60 mph gusty outflows and this correlates well with the SPC Day 1 Marginal Risk across much of Wyoming. Thunderstorms will also be capable of frequent lightning and the potential for small hail cannot be ruled out with steep mid level lapse rates. Showers and thunderstorms are forecast roughly from Noon through at least 1AM Tuesday, with the severe thunderstorm potential occurring between 1PM and 9PM.

Given today's shortwave will be working with monsoonal moisture and PWATs around the 90th percentile of climatology, any shower or thunderstorm will be capable of heavy rain and localized flooding. It is important to note that storms will be moving today with cloud layer shear in the 30 to 40kt range. The localized flooding issues arise if multiple storms traverse over the same area. The current forecasted QPF for today and tonight is a broad brushed 0.01 - 0.1 inches due to the overall scattered, but widespread coverage, nature of storms today. It is very difficult, if not impossible, to pin point the exact locations of showers and thunderstorms that could traverse over the same area and/or produce heavier rainfall rates.

On Tuesday, the aforementioned upper high will build northwards into the Great Basin with a ridge axis over Idaho. As this builds, another shortwave, although weaker than today, is forecast to traverse across Wyoming and bring additional shower and thunderstorm chances. Flow will be more west to west-northwesterly with the building ridge to our west, so monsoonal moisture is forecast to be greatest across west, northwest, and northern Wyoming. Given the weaker support aloft with overall height rises, showers and thunderstorms on Tuesday afternoon are forecast to be largely orographically and diurnally driven along and north of the Continental Divide.

The upper ridge slowly shifts east across Wyoming on Wednesday and Thursday with shortwave disturbances both afternoons. Wednesday currently looks to have less coverage and be largely terrain driven compared to Thursday. This is most likely due to height rises aloft suppressing more numerous convective activity. As the forecast currently stands, a more potent shortwave will be present as the ridge shifts east out of Wyoming on Thursday. This means that Thursday could be an active weather day for the area. Wyoming is currently forecast to be in southwest flow behind the ridge Friday through at least Sunday with embedded shortwaves each day. This ultimately means that another weekend with afternoon showers and thunderstorms is looking possible.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 513 AM MDT Mon Aug 24 2026

Showers and thunderstorms are forecast to develop across the state after 18Z/19Z. All terminals have at least a 30 percent chance of showers and thunderstorms at some point between the 19Z Monday and 06Z Tuesday. There is a reasonable amount of uncertainty with regards to direct impacts and timing of convection, so maintained PROB30s at this time. After the afternoon and early Monday evening thunderstorm chances end, lingering rain showers are possible at KJAC and KRKS and in the area of KCPR, KRIW, KLND, and KBPI. These chances are reflected in additional PROB30 or VCSH groups. Any showers or thunderstorms that are at or nearby a terminal will be capable of 35 to 45 kt winds, frequent lightning, heavy rainfall, and occasional mountain obscurations. Brief periods of MVFR to even IFR flight conditions cannot be ruled out if a shower or thunderstorm directly impacts a terminal. Otherwise, expect mid to high level clouds throughout the TAF period. Outside of any showers or thunderstorms, winds will generally remain around 12kts or less. Occasional gusts around 20 kts are possible at KCPR and KRKS Monday afternoon.

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

RIW WATCHES/WARNINGS/ADVISORIES

None.