textproduct: Western and Central Wyoming

KEY MESSAGES

- Scattered rain showers and isolated thunderstorms linger this evening, with rain chances increasing tonight overspreading the area from southwest to northeast.

- An approaching weather system will bring a good chance of showers to much of the area from later tonight into the weekend, with most rain across northern and western Wyoming.

- Accumulating snow is likely this weekend in the mountains, especially above 9500 feet.

- Temperatures will be much cooler this weekend rebounding next week.

UPDATE

Issued at 1230 PM MDT Fri May 29 2026

Seeing moisture on IR stream up from the southeast across areas east of the Divide. These mid to upper level clouds seem to be thin enough not to hinder forecasted high temperatures this afternoon in the Wind River/Bighorn Basins. Otherwise, the main upper level low continues to spin in a still pattern over Nevada that should start to progress northeastward finally in the next 6 to 12 hours. This will start to bring in the more widespread precipitation after midnight and much of Saturday and into Sunday. QPF amounts have diminished some, especially east of the Divide but most should still see at least the .1" wetting rain. The highest amounts continue to ping for Yellowstone and far northern parts of the Bighorn Basin. HREF models indicate the low becoming more progressive with each model run, and thus, should push out sooner Sunday late morning to early afternoon with only lingering light showers in its wake before weekend's end. Otherwise, cooler temperatures to more seasonable for this time of year still on track over the weekend and into early next week.

DISCUSSION

Issued at 230 AM MDT Fri May 29 2026

Meteorology is one of the physical and mathematical sciences. And the weather is basically governed by complex mathematical equations (some I would like to forget, I still have nightmares about dynamics class 28 years after I finally passed it). One of the most common is the sine wave, most often used with Rossby Waves. The weather often runs like a wave pattern with crests and troughs of different parameters. And we are currently in a crest and trough of one right now. On Thursday, we had the crest in temperatures, with a trough in coverage of precipitation. Starting today and especially going into this weekend, this is going to begin flipping.

The main reason is the cut off low that has been spinning across California and Nevada for the past few days. It will finally get a nudge and will begin heading northeastward toward Wyoming today. Moisture will begin to head back into the area, although it will take a while to deepen. There will be a few more showers and storms around today. However, most guidance shows it will be later show with some sticking around into the evening. With the flow turning southeast, the most impacted areas will be similar to yesterday, the favored upslope areas like around the east sloes of the Absarokas and the Bighorns as well as Natrona and Johnson County where moisture will build the fastest. Even here, the chance of a shower or storm is probably no more than 1 out of 3. It will be another very warm day, but with increasing cloud cover probably a few degrees cooler than yesterday. And there will again be a bit of a gusty breeze, especially in southwest Wyoming, where, combined with still low humidity, may bring elevated fire weather this afternoon.

Precipitation will really increase later tonight and into Saturday as the upper level low finally moves into Wyoming. Most guidance shows the same general pattern as yesterday, with a northwest to southeast gradient of QPF with the highest amounts in the west and north. Areas further to the east will likely having more of a southwest downsloping flow that will keep the precipitation more showery. Every location will have a chance of rain though. As for how much, we will take a look at the NBA ensembles for this. At this point, it is fairly similar to yesterday, with a greater than 1 in 2 chance of a quarter of an inch of QPF or more mainly north and west of a Evanston to Riverton to Kaycee line. The highest amounts still look to be in northwestern Wyoming and near the Bighorns though, with a greater than 1 in 2 chance of an inch of QPF or more. The Weather Prediction Center continues to have a marginal risk of excessive rainfall across northern Wyoming on both Saturday and Sunday. It has been fairly dry, so there is room in the soil. But it is something to keep in mind. Saturday continues to look like the wettest day. However, the low will likely slow down somewhat and stall over Montana. This will keep unsettled weather over parts of the area, with northern Wyoming the most impacted. How far south it can stay this way is in question, since there are differences in guidance as to when the low will lift out of the area.

Needless to say, it will be much cooler with the cloud cover and showers. This is especially so on the western side of the low where flow will be northerly. A place like Jackson may stay below 55 all weekend. And this brings us to another part of the system, the chance of snow. Yes any visitors to the Cowboy State, it can snow here any month of the year. Now, it will not accumulate in the lower elevations, and travel should not be impacted much as it has been very warm and the high sun angle would melt snow on roads. However, we do have a decent chance of some accumulating snow in the mountains. Some models drop the 700 millibar temperatures as low as minus 1, which would lower snow levels to 8000 feet. We still think this is too low, it would likely be closer to 9000 feet. Ares above 9500 feet in the western mountains have a greater than 1 in 2 chance of an inch or snow, and this includes Togwotee Pass. Some of the higher elevations of the Tetons and Wind Rivers could see 6 inches or more of snow this weekend. So if you are recreating in the mountains, prepare for a cold and wet weekend. You will also likely see some snow if you are driving over Togwotee Pass.

Early next week is in questions as well. Some guidance lingers the low close enough for some showers to linger into Monday, other favor flow turning more to the west-southwest for a warmer and drier pattern. For most of the next week, the consensus seems to be for warm but not hot weather and a couple of chances of mainly diurnal showers and thunderstorm as shortwaves moving through the largely zonal flow.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 517 PM MDT Fri May 29 2026

VFR flight conditions are forecast through at least 04Z at all terminals with increasing cloud cover ahead of an approaching weather system. Rain showers will approach from the south and first impact KRKS by 08Z, but could (30 percent chance) begin as early as 04Z. Rain showers spread to almost all other terminals between 07Z and 13Z with associated MVFR to IFR flight conditions. KCPR has the lowest chances (10-20 percent) of rain showers directly impacting the terminal this TAF period. Thunderstorm potential will generally increase after sunrise/12Z Saturday and continue to increase through the morning. Periods of moderate to heavy rain are possible.

After sunrise Saturday morning, low clouds and some fog are forecast with MVFR to IFR flight conditions. This is expected to persist after the overnight rain showers have diminished. Showers and thunderstorms are forecast almost the entire TAF period at KJAC and KCOD. All other terminals will likely see periodic showers and thunderstorms throughout the day Saturday. Otherwise, most terminals will see wind shifts throughout the TAF period with winds generally 10kts to 15kts. Wind gusts of 20kts to 30kts are expected to be most common at KCPR after 14Z and at KRKS, KPNA, and KBPI after 19Z.

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.