textproduct: Western and Central Wyoming

KEY MESSAGES

- Rather warm today. There will be some mainly afternoon showers and thunderstorms around, but much less numerous that yesterday.

- A weather system will bring cooler and damp weather to northwestern Wyoming with showers and some high elevation snow.

- Remaining warmer elsewhere this weekend with a gusty wind. Elevated fire weather is possible from Friday through Sunday for many locations in southern and central Wyoming.

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, this is my seventh night. And this is sixth of the seven days when 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 then 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 few points 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 dew point 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. 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 dew point 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 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 /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 942 PM MDT Thu Jun 25 2026

Precipitation will have ended across the forecast area by the start of the TAF period, briefly. An area of showers and storms will quickly develop over the Salt River/Wyoming Ranges around 07Z and dissipate as it moves into the Wind River Basin by 10Z. Confidence remains too low to include in the KBPI/KPNA forecasts. All terminals to be VFR through the period with the possible exception of MVFR low clouds at KCPR between 09Z and 13Z. However, southwest surface wind begins to increase at KCPR around sunrise leading to erosion of any low clouds that do form. Isolated showers will remain possible across areas east of the Divide between 12Z and 18Z. Gusty southwest wind 15-30kt 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, KWRL and KCPR, with a lesser chance at KRIW and KLND. This activity will push northeastward out of the area after 00Z, with mainly dry conditions through the end of the forecast period.

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