textproduct: Western and Central Wyoming

KEY MESSAGES

- Low humidity (10 to 20 percent) and breezy winds (gusts of 30 to 40 mph) will contribute to near-critical to critical fire weather conditions through sunset. A Red Flag Warning remains in effect for portions of the Bighorn Basin.

- Wind and low humidity will lead to continued fire weather concerns through the week. Confidence is increasing for a late week system to bring cooler and wetter conditions to the area.

UPDATE

Issued at 123 PM MDT Mon Sep 7 2026

With this morning's rain now finished, the focus returns to fire weather. As noted below, the greatest concern this afternoon is across the Bighorn Basin, though most areas east of the Divide will be near-critical given the gusty winds and low humidity. A very similar story is expected tomorrow though wind will not be quite as robust. Regardless, additional Red Flag Warnings may be needed Tuesday, potentially expanded through much of the upcoming week.

DISCUSSION

Issued at 235 AM MDT Mon Sep 7 2026

Showers continue to subside over the northern half of the forecast area early this morning, with isolated thunderstorms over far western portions. This precipitation will end across the area by 15Z this morning as winds begin to increase. A dry slot will be in place over the Cowboy State by this time, with the main sfc low in the vicinity of MT/ND and the associated occluded low over western MT. West-southwest winds, with gusts of 25 to 35 mph will be in place from Kemmerer to Casper by this time. Higher winds of 30 to 45 mph will occur over portions of YNP and the east slopes of the Absaroka, Bighorn and Wind River Mountains. Winds will continue to increase across the forecast area, with gusts of 25 to 40 mph occurring for most areas by 18Z. Fire weather will once again be a concern as a result, with near- critical RH values returning. This will be especially true east of the Divide, where critical RHs will be in place in the Bighorn Basin. A Red Flag Warning is in effect for Big Horn, Washakie and Hot Springs counties this afternoon as a result. A cold front will move eastward through the afternoon, exiting the CWA into southeast WY between 06Z and 09Z Tuesday. Winds will subside through the evening, becoming light for much of the area after midnight. Freezing temperatures will be possible in the western valleys and portions of the Upper Green River Basin Tuesday morning in the wake of the cold front.

More seasonal temperatures and dry conditions will remain in place Tuesday, with freezing temperatures possible again in the western valleys and Upper Green River Basin Tuesday night/Wednesday morning. Needless to say, sub-freezing temperatures will be in place in the higher elevations the next two nights. Fire weather will be the main concern through the rest of the week. West-southwest winds, with gusts of 25 to 35 mph, will occur each afternoon with slightly stronger gusts possible Thursday and Friday. Critical RHs will be widespread east of the Divide Tuesday, spreading across southern portions Wednesday. An extended period of Red Flag Warnings looks likely.

Models continue to trend toward a strong cold front impacting the Cowboy State next weekend. The GFS continues to be the most aggressive, digging a Canadian low southward to northern portions of the Great Basin and spreading widespread precipitation over the state ahead of it. The ECMWF is slower and not as progressive, keeping the system over the Northern Rockies and moving over the region Sunday into Monday next week. Although the timing remains influx, this continues to trend toward the first taste of autumn to the region.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 349 PM MDT Mon Sep 7 2026

VFR conditions through the period. The strongest winds from this afternoon decrease between 00z and 04z. Clouds also decrease for the overnight hours. A mostly clear sky is expected through Tuesday, with increasing clouds over northern Wyoming. Winds 20 to 30 knots occur at most sites Tuesday afternoon.

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 235 AM MDT Mon Sep 7 2026

Rain showers will end across the area by 0900 this morning, with conditions remaining dry through the rest of the day. Winds will increase across the area during this time with gusts up to 30 mph already occurring from Kemmerer to Casper. Higher gusts of 35 to 45 mph are expected in the mountains and northwestern portions by 0900 as well. Winds will continue to increase across the area through the rest of the morning, with gusts of 30 to 40 mph occurring for most locations by 1200. Critical RHs will be confined to zones 275/282 this afternoon, but other areas east of the Divide will have RHs ranging between 16 and 20%. A cold front will push into northern portions of the Bighorn Basin between 1300 and 1500, progressing to the south and east through the afternoon reaching Greybull/Basin by 1800. The front will pass through the rest of the Bighorn Basin by 2100 as winds decrease across the area.

Red Flag conditions are likely through the rest of the week, with multi-day Red Flag Warnings expected.

RIW WATCHES/WARNINGS/ADVISORIES

Red Flag Warning until 7 PM MDT this evening for WYZ275-282.