textproduct: Western and Central Wyoming

KEY MESSAGES

- Isolated to scattered shower and thunderstorms are forecast from 1PM through 9PM for many of the same locations as Tuesday, although overall coverage will be less. Showers and thunderstorms will be capable of gusty 45 to 60 mph outflows and frequent lightning.

- Shower and thunderstorm chances exist through early next week, with Friday and Saturday looking the most active, mainly across west and northwest Wyoming.

- Slightly above normal temperatures through Friday, with highs in the 70s and 80s. A few locations east of the Continental Divide could see highs in the 90s. A cool down to below normal temperatures is expected for Saturday and Sunday.

DISCUSSION

Issued at 213 AM MDT Wed Aug 26 2026

2AM satellite water vapor imagery shows two features that will influence the weather across Wyoming over the next 5 days. The first feature is an upper high centered over New Mexico and it's associated ridge axis positioned roughly along the western Wyoming border. Today, the ridge axis is forecast to remain in it's current location (far western Wyoming) with an embedded shortwave disturbance rounding it this afternoon. There will be enough moisture aloft for isolated to scattered showers and thunderstorms as the disturbance passes through. The location and initiation of showers and thunderstorms will be very similar to what occurred Tuesday afternoon and evening. That is convective initiation across the higher elevations of central and southwest Wyoming. Showers and thunderstorms are forecast to then shift east into the Green River, Bighorn, and Wind River Basins and into Sweetwater, Natrona, and Johnson Counties. However, chances of any of the aforementioned locations seeing a shower or thunderstorms are anywhere from 15 to 30 percent. Although coverage is expected to be less today due to weaker forcing aloft, gusty 45 to 60 mph outflows will be possible in any shower or thunderstorm. This is due to DCAPE values upwards of 1500 J/kg, a classic inverted-V sounding, and 40 to 45 degree dew point depressions. Shower and thunderstorm chances exist between 1PM and 9PM. A few lingering showers are possible across northwest Wyoming through midnight as the ridge begins to shift east. With the ridge largely overhead and 12 to 14C 700mb temperatures, expect widespread highs in the 80s, with a few locations reaching 90.

As mentioned previously, there is another feature present on satellite water vapor imagery and that is a trough currently off the Pacific Northwest Coast. By late tonight, this trough will begin to move onshore the Pacific Northwest and slowly help shift the upper ridge across Wyoming. The ridge will shift east across Wyoming through late Thursday. Flow on the upstream side of the ridge will become more southwesterly across the state as the eastern shift occurs. A shortwave disturbance, and an associated surface front, is forecast to move across Wyoming Thursday afternoon and evening. Deep available moisture will also begin to increase with this disturbance and front with PWATs in the 0.75" to 0.90" range (95th percentile of climatology) across west and northwest Wyoming. With all this in mind, showers and thunderstorms are forecast across the aforementioned areas Thursday afternoon and evening. Gusty 50 to 60 mph winds and frequent lightning will once again be the primary threats with any convection. Localized heavy rainfall is possible with the higher PWATs, however, storms are expected to be moving with 25 kt+ cloud layer winds. Thus, the flooding threat is rather low at this time. Thursday's high temperatures across western Wyoming are forecast to be right around 80 degrees and in the mid 80s to low 90s elsewhere across the state.

Ensemble guidance is in consensus that the ridge will be over the central CONUS and the upper trough be positioned over the Pacific Northwest on Friday. This ultimately places Wyoming in deep southwest flow with increasing Pacific moisture. Ensemble guidance is signaling that, by Friday afternoon, PWATs will exceed the 97th percentile of climatology. Southwest flow will only strengthen as the aforementioned trough slowly shifts east into the Intermountain West on Saturday. Additionally, embedded shortwaves are expected to traverse the state Friday and Saturday afternoon. This means that an active Friday and Saturday are forecast, especially across western Wyoming due to being in better proximity to the abundant moisture. As the forecast currently stands, a front will begin trekking across the state late Friday through midday Saturday. This front will be the focus of widespread showers and thunderstorms during this timeframe across west and northwest Wyoming. There is currently a 45 to 50 percent chance of at least 0.5" of rain from Friday night through Saturday night across northwest Wyoming. It is important to note that these details are bound to fluctuate as we get closer to Friday and more HI-Res model guidance becomes available. Regardless, this will need to be monitored over the coming days for moderate to heavy rainfall and any localized flooding. Temperatures on Friday are forecast to be comparable to Thursday across the area. Behind the front on Saturday, high temperatures are forecast to be 7 to 15 degrees cooler than Friday.

There is consensus that the Pacific Northwest trough and low will push east into the Northern Rockies on Sunday and provide support for another front to trek across the state. However, there are differences among deterministic model guidances on the exact trajectory of the low and the amount of associated moisture. Nevertheless, shower and thunderstorm chances exist with the frontal passage across the state. An active pattern looks to continue through the first half of next week, as shortwaves traverse across the state each afternoon.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 530 AM MDT Wed Aug 26 2026

VFR flight conditions are forecast through 12Z Thursday. Showers and thunderstorms will develop across the higher terrain of western and central Wyoming after 19Z and move east through the afternoon. Convection will be widely scattered today, so confidence in direct impacts at terminals is rather low. That being said, KCOD, KRIW, KRKS, KLND, KPNA, and KBPI have a 30 percent chance of seeing a shower or thunderstorm between 20Z and 03Z, respectively. Showers and thunderstorms at and around KJAC and KCPR are expected to remain over the nearby mountains, with less than a 15 percent chance of direct impacts. The primary hazards with any showers or thunderstorms will be gusty 35 to 40kt winds and frequent lightning. Outside of any thunderstorm activity, winds remain 10 kts or less at most terminals. Breezy afternoon winds with gusts around 20kts are forecast at KCPR and KRKS.

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.