textproduct: Western and Central Wyoming

KEY MESSAGES

- Isolated rain showers and thunderstorms continue through this evening across northern and southern portions of the area. Small hail, gusty wind, and brief heavy rain remain threats until storms dissipate by midnight.

- Shower and thunderstorm chances (20% to 40%) exist Friday afternoon across northwest and northern Wyoming as well as Johnson and Natrona County. Otherwise, expect warmer temperatures, lower humidity, and gusty winds on Friday with elevated fire weather conditions possible.

- 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.

- Wind will be breezy each afternoon for the next week, which will lead to elevated fire weather conditions. Possible critical conditions by the middle of next week.

UPDATE

Issued at 1005 AM MDT Thu Jun 25 2026

The forecast for today remains on track with showers and thunderstorms moving from west to east across Wyoming along a cold front. As of 10AM MDT, radar is showing a line of thunderstorms from the western Absarokas to western Sublette County. These thunderstorms will push east through the late morning and early afternoon, moving across the Green River Basin between 10AM and 12PM, the Bighorn and Wind River Basins between 12PM and 3PM and the I-25 corridor in Natrona and Johnson Counties between 2PM and 5PM. Confidence has increased in thunderstorms becoming strong to severe due to more cloud breaks across the area. Hi-Res guidance is indicating 1000 to 1500 J/kg of BLCAPE, 30 to 45kts of 0 to 6km shear, and unstable mid- level lapse rates around 7.5 C/km. This suggests that any thunderstorms will be able to produce heavy rainfall, small hail, gusty 30 mph to 45 mph winds, and frequent lightning with the line. Instances of 60 mph wind gusts are possible in thunderstorms that become severe.

Conditions are a bit different across southern and southwestern Wyoming, where there has been abundant morning sunshine. Across the aforementioned areas, very unstable lapse rates around 8.5 C/km, DCAPE values around 1,000 J/kg, and nearly 1,500 J/kg of BLCAPE are forecast this afternoon. Dew points have remained rather high this morning with Rock Springs Airport reporting morning dew points in the low 50s. This will help keep afternoon dew point depressions around 40 degrees fahrenheit. Thus, thunderstorms across southern and southwestern Wyoming will be capable of gusty 40 to 50 mph winds, hail up to 1 inch, and frequent lightning. All thunderstorm chances largely come to an end by sunset as daytime heating subsides.

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 /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 432 PM MDT Thu Jun 25 2026

The shortwave that produced a line of strong to severe convection has pushed east with improved conditions across most of the forecast area late Thursday afternoon. One plume of moisture remains across far southern Wyoming in the vicinity of KRKS Thursday evening, with another plume across northwest Wyoming near KCOD. Isolated showers and thunderstorms within these areas fade between 04Z-06Z/Friday. All terminals to be VFR through the period with the possible exception of MVFR low clouds at KCPR for a 4-hour period late tonight. However, southwest surface wind begins to increase at KCPR around sunrise leading to erosion of any low clouds that do form. Gusty southwest wind 15-30kts then increases at KCPR mid-morning followed by the other terminals between 16Z-20Z/Friday. There is still enough mid-level moisture to allow for late Friday afternoon thunderstorms at KJAC, KCOD, and KCPR, with a lesser chance at KRIW and KLND.

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.