textproduct: Western and Central Wyoming

KEY MESSAGES

- Isolated evening showers across mainly northwest Wyoming will be capable of producing 35 to 50 mph outflow wind gusts until sunset Friday.

- A weather system approaches Wyoming early Saturday and spreads light rain showers across western Wyoming. These showers, along with isolated thunderstorms, become more widespread over the region Saturday afternoon and evening.

- The weather system brings cooler temperatures to the state for the weekend, with daytime highs Saturday and Sunday about 5 to 15 degrees cooler compared to Friday. However, gusty 25 to 40 mph winds bring elevated to near critical fire weather conditions both afternoons.

- The cooler temperatures may allow for some high elevation snow in the mountains of west and northwest Wyoming. Monday morning low temperatures in the western valleys and basins could fall into the upper 20s.

- A warm up, mostly dry conditions, and breezy winds are forecast Monday through the end of the next week, so elevated to near critical fire weather conditions are looking more favorable.

UPDATE

Issued at 1202 PM MDT Fri Jun 26 2026

Today's forecast largely remains on track for this afternoon and evening as southwest flow strengthens across Wyoming. 18Z/noon observations indicate that the drier and warmer air has reached southwest Wyoming, with dewpoint readings in the 20s and 30s and temperatures around 80 degrees Fahrenheit. This translates to relative humidity values already in the low 20s and teen percent range. Low level moisture is hanging around a bit longer across central and northern Wyoming, with dewpoints in the upper 40s and 50s. These higher dewpoints are likely due to Thursday's beneficial rain. As southwest flow strengthens and expands across the state this afternoon, the air across central and northern Wyoming will dry out and warm up. Winds will also increase across the entire state ahead of an approaching late evening cold front. Widespread wind gusts of 30 to 40 mph are forecast between 2PM and 7PM. These gusty winds will further aid in drying out the atmosphere, so elevated to near critical fire weather conditions are anticipated this afternoon, especially across southern Wyoming.

In addition to the fire weather concerns, the isolated virga, showers, and thunderstorm potential mentioned in the morning discussion remains. The greatest chances (15% to 40%) exist along and east of the Continental Divide, excluding the Wind River Basin. Given the dry low level air, afternoon LCL's are expected to be in the 11,000 to 13,000 ft AGL range across the Bighorn Basin and Johnson and Natrona Counties. With LCL's this high and dewpoint depressions in the 40 to 50 degree range, any virga, shower or thunderstorm, will be capable of 45 to 55 mph gusts as it collapses. Chances are much less (<10%) across southern Wyoming this afternoon, but should anything be able to develop gusts of 55 to 60 mph would be possible. The best time frame for any virga, showers, or thunderstorms is 1PM to 8PM. As for Saturday, showers are still forecast across western Wyoming and drier elsewhere. Fire headlines were considered for Natrona County for Saturday afternoon but conditions still look borderline, so no headlines were issued at this time.

DISCUSSION

Issued at 138 AM MDT Fri Jun 26 2026

I returned from a vacation about a week ago, and have worked straight through since then. It seems like I am cursed when it comes to thunderstorms. Since I went back to work on Friday night, we have had at least a Marginal risk in portions of our County Warning Area (June 21st was the only day there wasn't one). If I didn't have to see another thunderstorm this summer, I would be delighted (not going to happen, but I can wish). And, what a surprise, we have another one today, although just a small part of the area.

And this is courtesy of another shortwave that will be rotating into the area as an upper level low moves onshore in the Pacific Northwest. Coverage should be less than previous days though. Most activity should be across the northern half of the area. The season will be southwest flow that will move in ahead of the low. This will do a few things. One, it will bring the warmest day we have had in a while to these parts, with many locations east of the Divide. But in regards to the weather, it should limit develop of convection to the northern half of the state. Southwest flow should allow much drier air to move into the southern half of the state, dropping dewpoints into the 20s and 30s. This should be enough dry air to shut off convection during the day. The chance of showers and storms looks to be roughly north of a line from Jackson to Riverton to Casper, where more humid air will linger today. But even here, the atmosphere is about 25 percent drier than yesterday so coverage will be at most 1 out of 3 for any spot except for the northwestern mountains. Instability parameters are not as impressive either, with only the northern portions of Johnson, Natrona and Park Counties having CAPE of more than 500 J/kg. This is also the location of limited indices of minus 2 or lower. Shear also increases as you go further north, hence the better chance of stronger storms. The main threat today looks to be strong wind gusts as soundings are showing more inverted-V signatures and most locations will have at least a 40 degree dewpoint depression in the afternoon. The third concern is fire weather. The 700 millibar winds are around 30 knots and these will mix to the ground for many areas. Elevated fire weather has a greater than 4 out of 5 chance in southern Wyoming, but no highlights since fuels are not critical. The one zone that is critical that may get close is Washakie County, but it looks to remain just high enough.

Chances for showers will increase across the west on Friday night as the flow moves closer. It may take a while to moisten the atmosphere though, so most PoPs were held off until after midnight, and any steadier showers would likely hold off until after sunrise on Saturday. Most guidance keeps the low west of Wyoming as it turns northward and into Montana. That will lead to a northwest to southeast gradient of precipitation chances across the area, with the highest obviously in the northwest. It will be quite a contrast, with western Wyoming having more cloud cover along with cool temperatures and numerous showers. Meanwhile, continued downsloping southwest flow will bring another windy and warm day to many areas east of the Divide. There will likely be a few showers and thunderstorms around, but the chance is only around 1 out of 5 for most and many areas will see nothing. And with low humidity remaining, another day of elevated fire weather. I did give a brief thought of a Fire Weather Watch for Natrona County, but again with the conditions borderline, we held off for now. And, what a surprise, wait for it, we have another Marginal Risk, but only for the far northern portion of our area again. The main threat again will be strong wind with the rather large dewpoint depressions.

Cooler air will begin to move into the area on Sunday. It will be the same general pattern with cooler weather in the west and warmer weather in the east with the continued downsloping flow. There will be further showers in the west. However, recent model runs have shifted the deeper moisture to the west, so amounts have backed off. It will still be a cool and damp day. And we have to talk about chance of snow. With the deeper moisture further to the west, amounts look smaller. However, many locations in the northern mountains still look to have a greater than 1 in 2 chance of an inch of snow this weekend into the first part of Monday. The only place with a higher than 1 in 2 chance of 3 inches are the very highest peaks of the Wind River Range. Not nearly enough for highlights, but people heading to the high country should be aware of wet and cold weather this weekend. Only isolated showers and storms are again expected east of the Divide.

Things look generally drier next week. We will be stuck between a strong ridge across the eastern United States and a mean trough across the West Coast. This should keep southwest flow across the area with gradually warming temperatures. There will be a few chances of showers and storms with shortwaves moving through, but exact timing of them remains in flux.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 440 PM MDT Fri Jun 26 2026

Gusty winds decrease through about 08Z tonight, though elevated winds around 10 knots persist at many sites overnight. Winds increase for Saturday afternoon, with widespread gusts 25 to 40 knots. Shower chances occur Saturday morning for western locations (KBPI/KPNA/KJAC). Showers and thunderstorms are then possible for all locations during Saturday afternoon; have left PROB30 groups for now given uncertainty at this time range, but best chances look to occur across northwest Wyoming, including KCOD and KJAC.

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

FIRE WEATHER

Issued at 138 AM MDT Fri Jun 26 2026

A combination of a gusty wind, humidity falling into the upper teens and dry fuels will bring elevated fire weather to much of central and southern Wyoming. A few dry thunderstorms are also possible. Elevated fire weather continues east of the Divide as well as southern Wyoming with a continuation of low humidity and a gusty southwest wind continues.

RIW WATCHES/WARNINGS/ADVISORIES

None.