textproduct: Western and Central Wyoming

KEY MESSAGES

- South-southeast flow continues to bring clouds over most of western and central WY today under very warm and breezy conditions. Afternoon high temps will reach the low 80s to low 90s in the lower elevations (about 15-15 degrees above normal). Isolated showers and thunderstorms are possible again this afternoon from Casper Mountain northward to the Bighorn Mountains, as well as from Dubois northward into the Absarokas and YNP.

- Similar conditions are expected again on Friday, though southwest WY will see increasing clouds and cooler temperatures late in the afternoon and evening due to a storm system approaching from the southwest.

- A weather system approaches Friday night into Saturday morning with a good chance for showers and isolated thunderstorms across all of western and central WY. The heaviest precipitation looks to fall in western Wyoming and over the mountains, but exact amounts are still uncertain. Temperatures will cool to the upper 50s across southwest WY and 70s across north-central WY on Saturday, with below normal temperatures remaining through Monday.

- Elevations above 9000 feet may see accumulating snow over the weekend, with the highest amounts in the Tetons, central to northern Wind Rivers, and southern Absarokas. YNP could see around an inch of precipitation over the weekend as well.

DISCUSSION

Issued at 1238 AM MDT Thu May 28 2026

We continue to have the two main players in our weather this morning. In the right (east) we have a ridge over the Plains States. And in the left (west) corner we have a bowling ball, AKA a closed low that has been cut off for a few days over California and Nevada, just meandering a bit from time to time. The trend for daily convection has been downward. The with heights continuing to build, it will likely reach a minimum today. Much drier air will continue to move eastward, with below a half an inch or precipitable water covering most of western and central Wyoming by later this afternoon. Any thunderstorms would be limited to far northern and northeastern areas. There could be a couple near the Absarokas and Big Horns where some weak upslope or high level heat source may bring something but even here the chance is less than 1 out of 5. The main story today will be the warm temperatures, with some of the warmer areas, like the Bighorn Basin, having some areas that eclipse the 90 degree mark this afternoon. There will also still be a bit of a breeze today, but somewhat lighter than yesterday. Areas in northern Johnson County still have around a 1 in 2 chance of gusts over 35 mph at times this afternoon though. Any convection should end fairly quickly this evening, with dry weather after midnight.

Things should finally start moving on Friday as the ridge weakens and shifts a bit east and the low begins to move. Flow will turn more to the southeast through the day and increase moisture into the area. It will take a while for the atmosphere to moisten though. As a result, most of the day should be warm and dry with any convection holding off until mid to late afternoon. Temperatures should run fairly similar to today's highs.

It is looking more and more likely that at least portions of the area will see a decent amount of precipitation over the weekend. Where it falls depends upon where the low eventually tracks and both the ensembles and deterministic models continue to have different solutions. A further west track, like some ensemble members as well as the GFS have, would keep the heavier precipitation over western Wyoming. Areas further east would have a downsloping flow and therefore less precipitation. If the low is further east, decent precipitation would be spread more throughout the area. The Weather Prediction Center does have northern portions of the area in a marginal risk of excessive rainfall as well for both Saturday and possibly Sunday as the low may slow down and linger close to the area, but again there are solutions on both sides of this equation. As for precipitation amounts, we will turn to the realm of the ensembles to try to answer this question. The National Blend of Models gives a greater than 1 in 2 chance of a quarter of an inch of QPF through Monday morning roughly north and west of a Rock Springs to Riverton and Buffalo line. Much northwestern Wyoming, including Yellowstone Park, the Absarokas and Tetons have a greater than 1 in 2 chance of an inch o QPF or more. Still some uncertainty for exact placement, but the chance is definitely there.

And then we have to take a look at the possibility of the "S" word, snow. Yes, there could be some snow with this system. It will not occur in the valleys. However, we are getting into the time of year when mountain recreation increases substantially we have to look at it. The GFS gives 700 millibar temperatures falling as low as minus 1, which would put snow levels around 8000 feet. This may be a bit low, it likely closer to 8500 or 9000 feet. However, there could be some accumulation. The National Blend of Models gives a greater than 1 in 2 chance of 3 inches of snow above 10000 feet through Monday morning. Some of highest peaks in the Wind River Range and Tetons could see 6 inches or more of snow from this. It doesn't look to impact travel to substantially since roads are very warm right now. However, if you are traveling over mountain passes, don't be surprised if you see some snow this weekend, especially over the higher ones like Togwotee Pass which is close to 10000 feet in elevation.

Following this, drier weather looks to return to the area and flow becomes more zonal with flat ridging bring drier weather and temperatures returning to much of the area for the start of next week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1030 AM MDT Thu May 28 2026

VFR conditions expected throughout the entirety of the period at all TAF sites. Increasing winds shortly after the start of the period through the afternoon hours during peak heating and mixing to the surface. Isolated storm chances near CPR/COD once again with PROB30 groups between 20-23Z but confidence low (<10%) on station. Winds diminish after around 02Z towards sunset with radiational cooling expected to pick up once again by the end of the period towards 17-18Z. Storm activity only expected near CPR for Friday afternoon into the next TAF cycle.

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

RIW WATCHES/WARNINGS/ADVISORIES

None.