textproduct: Western and Central Wyoming

KEY MESSAGES

- Mostly clear skies and tranquil weather conditions continue through tonight. Lows will be 5-10 degrees warmer than last night.

- There is a 10% to 15% chance of virga and/or light rain and a few rumbles of thunder Monday afternoon and evening across northern Wyoming. Across the Bighorn Basin, gusty outflows of 45 to 55 mph will be the primary threat, even with no rain.

- A combination of very warm temperatures, very low humidity (less than 15 percent), and gusty winds will bring elevated to near critical fire weather Monday afternoon through much of the work week.

- Well above normal temperatures in the 80s, and potentially in the low 90s, are expected much of this week. Record high temperatures are possible each day Monday through Thursday.

UPDATE

Issued at 1148 AM MDT Sun May 10 2026

A tranquil afternoon continues this afternoon with only a few cirrus clouds passing over. This pleasant weather is all thanks to subsidence from high pressure across the area. Today's high temperatures (widespread 70s) are forecast to be the "coolest" highs through at least Thursday. There is still high confidence in widespread highs in the 80s beginning Monday with increasing wind. The elevated to near critical fire weather conditions remain each afternoon through Thursday.

The forecast largely remains on track for Monday afternoon and evening as a weak shortwave traverses over the region. It looks as if there will be some accompanying mid-level moisture across northern Wyoming with the passing shortwave. Because of this, light rain chances (10% to 15%), and some thunder, have been added to the forecast beginning around 3PM MDT Monday across northwest Wyoming. As the shortwave progresses eastward, these chances also shift east across the Bighorn Basin and into Johnson County. Confidence in anything actually making it to the ground is relatively low, with virga being the most likely scenario because of the dry low levels. For the Bighorn Basin, gusty 45 mph to 55 mph, and potentially closer to 60 mph, downdrafts and outflows are possible even in the absence of any liquid making it to the ground. This is largely due to dew point depressions in the 45 mph to 55 mph range. Outside of these low rain/virga chances, Monday will still be a windy day as the shortwave passes over.

DISCUSSION

Issued at 144 AM MDT Sun May 10 2026

Many meteorologists are shift workers, and are often more tired than many people. And what do you drink when you need energy? For most people, that is coffee (myself excluded, I never developed a taste for coffee and usually only drink water on shift). And one of the things people put in coffee reminds me of weather this weekend. And that is half and half.

The active half was yesterday, with showers and thunderstorms, and even a brief landspout tornado. Temperatures were also below normal as well. The shortwave that caused this has now moved away from the area, and ridging will build across the area today, bring a very nice spring day to end the weekend. Temperatures should average 5 to 10 degrees above normal, comfortably warm for most. There should be plenty of sunshine as well with only some passing high clouds and some cumulus near the mountain ranges. In addition, wind should remain light to moderate, although some locally breezy conditions are possible. If you can, get out and enjoy it.

We then turn to something we have seen much of this calendar year, even dating back to last fall. This relates to a song I heard this evening while listening to 80s music. The song was "The Heat Is On" by the late, great Glenn Frey (cue sax solo). Of course, I am referring to another period of likely record high temperatures. The 700 millibar temperatures will be on the rise, from an average of 7 celsius today to 10 to 12 celsius on Monday to as high as 15 celsius on Wednesday. As a result, temperatures will average 15 to as much as 20 degrees above normal through the period. Assisting in the warming on Monday will be a weak shortwave moving through the flow. There is little moisture with it, with only only a less than 1 in 5 chance of a mountain shower or thunderstorm Monday afternoon. The main impact will be mix the atmosphere and mix some 30 to 40 knot 700 millibar winds to the surface, aiding in downsloping and further raising temperatures. Many locations will be into the 80s, some locations well into the 80s. Chances of reaching 90 are small this day though, less than 1 out of 4 any only in warmest spots like Basin and Worland. The main concern on this day will be elevated to near critical fire weather, as humidity will fall into the teens for most locations, even the single digits. No fire weather highlights will be issued at this time since fuels aren't critical, but burning is not advised on this day.

The ridge axis then builds over the area on Tuesday. With less mixing and wind, temperatures should cool somewhat East of the Divide, but still remain well above normal. The heat will likely peak on Wednesday, as the wind increases somewhat and 700 millibar temperatures peak. This will likely be when high temperatures will peak. At this time, there is a greater than 2 out of 3 chance of a high temperatures over 90 across the warmer locations like from Thermopolis to Greybull in the Bighorn Basin. This would be around 2 and a half weeks before the average first 90 degree high, but not the earliest at most locations here. Chances are lower elsewhere East of the Divide, generally 1 in 4 to 1 out of 3. However, it would tie or set the earliest appearance of 90 degree temperatures in locations like Riverton, Casper and Lander. At the same time, some moisture returning to the west ahead of an upper level low approaching the west coast may bring a few showers and storms to the west, but most locations will not see one.

There will likely be one more day of warm weather on Thursday before cooler air returns as the Pacific low approaches. Confidence is very low on what will happen with this system as some deterministic and ensemble members bring a secondary piece of energy over Wyoming Friday with a decent amount of QPF, while others keep the precipitation largely over Montana. At this point, there continues to be a lot of uncertainty, stay tuned.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 539 PM MDT Sun May 10 2026

VFR conditions are forecast over the next 24 hours. Light breezes generally under 15 kt are expected for the evening and overnight hours, with mostly clear skies and no precipitation.

On Monday afternoon strong mid-level winds will mix down to the surface, with widespread gusts of 30 to 40 kt for much of the region. Scattered high cirrus clouds thicken, but low clouds are not expected for most locations. There are hints of a few showers attempting to move into the vicinity of KCOD late afternoon, but current forecast remains at a low probability (<20%).

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

FIRE WEATHER

Issued at 144 AM MDT Sun May 10 2026

It will be much warmer today with humidity falling into the teens, but wind should remain light to moderate. On Monday, a weak weather system will approach and bring gusty to strong wind. With humidity falling below 15 percent and temperatures well above normal, elevated to near critical fire weather is likely for many areas Monday afternoon.

RIW WATCHES/WARNINGS/ADVISORIES

None.