textproduct: Western and Central Wyoming

KEY MESSAGES

- Shower and thunderstorm chances (15 to 40 percent) today are greatest across Johnson and Natrona Counties, as well as for the Wind River and Absaroka Mountains and Yellowstone.

- Warm today, with gusty south to southeast winds through late this evening across northern Wyoming.

- Slightly warmer Thursday, with less rain chances. Most areas remain dry, with chances confined near mountains.

- A weather system approaches the area Friday night and Saturday, bringing better chances for rain. The greatest chances are across western Wyoming.

UPDATE

Issued at 1232 PM MDT Wed May 27 2026

Have updated precipitation chances given the latest hi-res models. The overall look to today remains the same, with 15 to 40 percent rain shower/thunderstorm chances over Johnson and Natrona Counties, as well as over the northern Wind River Mountains and across the Absaroka Range into Yellowstone. An isolated (15 percent chance or less) shower or storm can't be ruled out elsewhere, but those mentioned locations are the most likely areas. Like has been the trend the last few days, any activity wanes after sunset and should be completely done by 10pm. Gusty outflow winds are the main hazard, with gusts 30 to 45 mph the most likely high end range.

DISCUSSION

Issued at 1254 AM MDT Wed May 27 2026

I am thinking of another childhood memory as I was composing the forecast tonight. One of the traditions of being home sick from school in the pre-internet age was watching daytime TV. And one of the most popular shows was (and still is), the Price Is Right. Our weather pattern this morning remains me of one of the games on that venerable game show, Squeeze Play. It relates to the current weather pattern as we are trapped between the cut off upper level low rotating near the Sierra Nevadas and a strong ridge to the east.

For today, it is showing off with our precipitable water values. They are projected to be above normal as much as 150 percent in some locations east of the Divide. Meanwhile, areas west of the Divide are below normal. This would imply the greater chance of convection shifts here today. But, there are a couple more factors. Instability is less, as heights have risen by around 50 decameters. There is also only half as much projected CAPE as yesterday (350 J/Kg today versus 700 J/Kg yesterday), so coverage may be less. The last thing we look at is the mean flow, and that is largely south- southeast with the squeeze play between the low and the ridge. This leads me to think that the best chance of convection would be close to areas where this flow is upslope. This means locations like along and east of the Absarokas and the Bighorns, for places like Park, Johnson and Natrona counties as well as portions of the Wind River Basin and Yellowstone National Park. But given the more limited instability, coverage looks less, generally less than 1 out of 4 or less. The squeeze play will have one more impact, the wind. There is a decent pressure gradient in the eastern portions of the area. The NBM ensemble is showing a greater than 2 in 3 chance of wind gusts past 30 mph in the Bighorn Basin and Johnson County. The strongest wind would be in Johnson County, where there is 1 in 2 chance of gusts around 40 mph this afternoon as we reach peak mixing. Temperatures should be similar to yesterday, about 5 to 10 degrees above normal but no extremely hot conditions. Most convection looks diurnal today, with most showers and storms ending after sunset.

At this time, convection looks to reach a nadir on Thursday, as drier air surges further eastward across the state, with the 0.50 inch precipitable water line enveloping most of western and central Wyoming. Any convection this day would likely remain close to the mountains with high level heat source and upslope flow, mainly of the south to southeastern variety again. The vast majority of locations, especially in the lower elevations, should remain rain free. Wind should also be lighter except for Johnson County, where a gusty wind will continue. High temperatures should run near to a couple of degrees warmer than Wednesday.

Chances of showers should begin to rise somewhat on Friday as the cut off low begins to get kicked eastward by the next trough approaching the West Coast. The atmosphere will be very dry to start though, so this could end up being a later show. Placement is also uncertain as a lot depends on how quickly deeper moisture can be advected into the area. The current forecast looks like a reasonable compromise, although most of the day should be rain free.

There is now decent agreement in the low opening up a bit and lifting northward Friday night and moving into western Wyoming on Saturday. This looks like the wettest day as a result. The exact path of the low will be critical though. If it tracks further west, many areas east of the Divide may have a southwesterly downsloping flow which would keep showers and thunderstorms to a minimum. The current forecast has this shown fairly well, with the highest PoPs in the northwest then tapering them down the further south and east you go.

Then more uncertainty creeps into the forecast for Sunday and early next week. Some models and ensemble members show the low cutting off again and lingering near the area into early next week, keeping the forecast cooler and unsettled. Others lift it out and bring a southwest flow which would bring warmer weather and mainly chances of diurnal convection. It is a coin flip which one will win out at this time though.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 345 PM MDT Wed May 27 2026

VFR conditions expected throughout the entirety of the period with breezy winds and mid level clouds to start the period overnight. Lingering showers near COD/CPR have started diminishing and out of the VCTS radius at this point in time but keeping PROB 30 groups going. Winds diminish after 02-03Z with radiational cooling expected to increase once again by 18-20Z Thursday afternoon with peak heating and mixing to the surface. Storm activity possible once again near COD/CPR similar to today, carrying PROB30 groups after 20Z, although not expected on station and only close to the VCTS radius (<10% confidence).

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.