textproduct: Western and Central Wyoming

KEY MESSAGES

- Another round of thunderstorms today, some could again be strong with heavy rain, hail and strong wind. These storms should end around sunset.

- Drier and warmer on Friday with elevated fire weather likely across much of the area in the afternoon.

- A weather system will bring a cooler weekend, especially on Sunday. Some accumulating snow is possible in the northwestern mountains from Saturday night through Sunday night.

DISCUSSION

Issued at 241 AM MDT Thu Jun 25 2026

There was interesting occurrence around Riverton last night. A severe thunderstorms developed off the Wind River Range and moved north. Just to show how tight the gradient can be on precipitation. At our office, we were missed for the most part and only had a trace of rain. Meanwhile, just 7 miles away, on the east side of Riverton, one of our retired forecasters reported 1.40 inches of rain in around 40 minutes and penny sized hail. There was a fair amount of street flooding in town as well. We still have showers and a few thunderstorms around as I write this around 1 am, but the trend is down as we lose instability. There will still be some around through the night though.

We will likely see more showers and storms today. There is some uncertainty though. For one, especially across eastern portions of the area, we will likely have a decent amount of cloud cover around to start the day. This could limit instability somewhat. However, there will some factors for it. Another shortwave will be crossing the area. There will also still be some directional and speed shear, although less than yesterday, generally between 30 and 40 knots versus the 50 to 60 we had on Wednesday. Some models still have a decent amount a CAPE through, up to 1500 J/Kg on the GFS for instance. As for stronger storms, the Storm Prediction Center has removed the slight risk. We now have a Marginal risk which runs largely south and east of a Worland to Thermopolis to Riverton to Rock Springs line. The main threat today would be strong wind, but there is enough shear and steep enough lapse rates for some marginally severe hail as well. And, heavy rain will be a threat again as the atmosphere remains rather moist. Precipitable water values are around 20 percent less than on Wednesday. However, this is still around 150 percent of normal. There are two other differences. One, there will be more 700 millibar flow, so storms should be faster moving, limiting the flooding threat more. And, unlike today, this looks like and earlier show, with almost all storms over by sunset as the shortwave exits the area stage east.

Shortwave ridging should build over the area on Friday and bring a quieter day. Not a quiet day by any means, but quieter. Precipitable water fall to near of even below normal levels across much of the area. The current forecast is more than likely the wettest it will be, most locations, especially East of the Divide, will likely have a dry day. Southwest flow will increase ahead an incoming upper level, and downsloping flow should bring a warm to hot day to most of the area. Some of the lower elevations East of the Divide will likely see highs in the 90s on this day. With relative humidity falling into the into the teens across southern Wyoming, elevated fire weather looks likely in the afternoon.

The aforementioned upper level low will begin to approach the area on Saturday. Most guidance has come into agreement in keeping the low largely west of Wyoming, and this should keep most of the precipitation across western Wyoming. Again, the current forecast East if the Divide is probably the wettest it will be, as downsloping flow will keep most of the day dry. The main concern will be across western Wyoming, where the best precipitation will be. And especially so from Saturday night into Sunday night. Much cooler air will move in here, dropping 700 millibar temperatures down to around minus 1 to minus 2, lowering snow levels to around 7500 to 8000 feet. Amounts don't look heavy, put there is a greater than 1 in 2 chance of an inch of snow above 9000 feet. So, if you are heading to the high country this weekend be prepared for some wet and cold conditions.

Conditions should gradually dry out starting Monday as the upper level low continues to lift northward. This will be followed by southwest flow dominating early next week, bringing warm but not hot temperatures. A couple of shortwaves may bring a few showers or thunderstorms, but timing of the waves remains uncertain at this time.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 434 AM MDT Thu Jun 25 2026

Areas of showers in the morning should exit to the east by around 14Z this morning. A few lingering showers may exist further west until another shortwave moves through the area and brings the next chance of convection. This wave will enter western Wyoming around 16Z Thursday and exit to the east by 02Z Friday. With uncertainty continuing with pinpointing convection, we have kept the previous forecast with only a few minor changes with prevailing showers and storms near KRIW and KLND where confidence is highest and PROB30 groups in other TAF sites where timing remains somewhat uncertain. App precipitation should end by sunset tonight.

Lingering moisture from last nights convention may will bring occasional IFR ceilings in vicinity of KLND with lower ceilings near KCPR with morning rain showers until around 14Z. Other terminals may be brief MVFR conditions as the showers and thunderstorms move through, otherwise mainly dry conditions continue through the TAF period. TAF sites west of the Divide will see wind gusts to 20 to 25 knots today before diminishing around sunset.

RIW WATCHES/WARNINGS/ADVISORIES

None.