textproduct: Western and Central Wyoming

KEY MESSAGES

- Warm today with highs ranging from the 80s to low 90s. Afternoon virga, showers, and thunderstorm chances (20% to 30%) along and east of the Continental Divide. Gusty 45 to 55 mph outflows are possible even in virga.

- A weather system will bring cooler (highs in the upper 50s and 60s) and damp weather to western and northwestern Wyoming with showers and some high elevation snow.

- Remaining warmer elsewhere this weekend with gusty 35 mph to 40 mph winds. Elevated fire weather is possible from 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 /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 419 AM MDT Fri Jun 26 2026

Most terminals should be VFR through most the TAF period. Isolated showers will be around through 18Z but not enough confidence to pinpoint at this time. Increasing southwest flow will bring a gusty wind with gusts to 15 to 30 knots likely at most TAF sites with the earliest and strongest gusts likely in vicinity of KCPR then at all terminals by 19Z. Lingering moisture may bring an isolated shower or thunderstorm, mainly to the northern terminals, mainly in vicinity of KCOD, KCPR, KJAC and KWRL after 18Z and ending by 00Z. A shower or thunderstorm can't be ruled out at KRIW and KLND, but with the chance less than 20 percent we left it out of the forecast for now. Increasing moisture will bring lowering ceilings at KBPI, KPNA and KJAC after 06Z Saturday but most precipitation should hold off until after 12Z Saturday except in vicinity of KJAC.

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.