textproduct: Western and Central Wyoming

KEY MESSAGES

- There is a 15 to 30 percent chance for a shower or thunderstorm through about 8pm today for far northern Wyoming, including the Absaroka Mountains, far northern Bighorn Basin, and northern Johnson County. A strong storm is possible around northern Johnson County, which could bring strong winds up to 60 mph and small hail.

- Elevated to near-cricital fire weather conditions occur today and through this weekend, with widespread gusty winds (20 to 40 mph) and low humidity (less than 15 percent).

- Hot Saturday, with highs in the 80s west of the Divide, and mid-to- upper 90s east of the Divide. Cooler air moves in for Sunday, dropping highs around 10 degrees and bringing slight (15 to 40 percent) rain chances, mainly for northern Wyoming.

UPDATE

Issued at 956 AM MDT Thu Jun 4 2026

No major changes to the forest with this update. Current water vapor shows the shortwave moving through northern Wyoming at this time, with a decent number of clouds. This feature tracks eastwards through this evening. The main result of this is the chance for showers and thunderstorms, some of which could be strong to severe. The better threat for strong storms exists north and east of the area, but northern Johnson County could see a strong storm between 3pm and 7pm; the main hazards are winds up to 60 mph and small hail.

DISCUSSION

Issued at 243 AM MDT Thu Jun 4 2026

KRIW radar noting very light echoes this morning moving across northern WY from the the Northwest Parks into the Bighorn Range. Most of these are very high based, and dry air near the sfc is keeping most precip from actually reaching the ground. These showers are due to a passing shortwave across western WY north into Montana. The shortwave will be mostly through the area by noon, but showers and thunderstorms may linger across the northern Bighorns and northern Johnson County into early afternoon. With daytime heating and instability, some development of strong thunderstorms could build quickly in these areas before sweeping quickly to the northeast by mid-afternoon. Main threat with these storms would be gusty downburst winds due to very dry sfc conditions.

Farther to the south away from the shower activity, the pressure gradient around this system is tighter, which will result in some gusty southwest winds this afternoon. Forecast gusts range from 30 to 40 mph from KRKS across the Green Mountains into Natrona County. This along with dry air already in place across the state will lead to near-critical fire weather concerns this afternoon. With most areas still in spring greenup, fuels are less receptive, so Red Flag Warnings will not be posted, but any fires that do spark will still have erratic behavior. Any burning is not advised today.

Once this system moves off this evening, the pattern buckles across the northern Rockies as a large trough drops down the west coast. This puts most of Wyoming in favorable ridging, deflecting systems away and allowing temperatures to soar. With H7 temps still forecast to reach 16 to 18C, sfc temps will jump well into the 80s west of the divide and into the 90s east of the Divide. Models have been trending upwards the past few days, with the latest forecast getting closer to daily record highs, and a couple areas within striking distance of 100 degrees.

Longer term forecast notes the west coast trough shifting farther east, knocking temperatures back down closer to normal. This will also shift better moisture into western WY, bringing a better chance for daily thunderstorms along the higher elevations of NW WY.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1130 AM MDT Thu Jun 4 2026

As a weather disturbance moves through southern Montana today, clouds are increasing across northern WY, with isolated showers and thunderstorms this afternoon and early evening from a line just south of KCOD to around KBYG. Some storms just east of KBYG could be stronger and produce very gusty outflow winds and large hail. VFR conditions are generally expected still as the system moves through, though KCOD has a 10% chance of MVFR conditions from about 04/22Z to 05/03Z. KCPR has has a 5-10% chance of MVFR early Friday morning as the cool front pushes low level moisture southward along the Bighorns into Natrona County. Gusty north winds with a cool front have already pushed into the Bighorn Basin shifting winds at KCOD and KWRL. Gusty north winds are expected to push into KCPR around 05/02Z, with a 10-15% chance of showers there around 05/06Z. The north winds will also push into KRIW around 05/04Z. Otherwise, dry west gusty winds with occur this afternoon at all other TAF sites, with gusts reaching 25-30 kts at KRKS. Some low- to mid-level clouds are expected east of the divide overnight, but should burn off quickly Friday morning. Skies clear out quickly west of the divide by 05/06Z.

High pressure builds back in Friday for mostly clear skies and gusty southwest winds, with VFR conditions expected from Friday mid-morning through the end of the day.

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.