textproduct: Western and Central Wyoming

KEY MESSAGES

- Elevated to near critical fire weather conditions are expected today for much of the area given low humidity, gusty winds, and warmer than normal temperatures.

- Strong wind ahead of a cold front will lead to a more widespread fire weather threat on Wednesday. A Fire Weather Watch is now in effect for locations east of the Continental Divide.

- Rain and mountain snow is expected across western Wyoming on Wednesday. A Winter Weather Advisory is now in effect for the western mountains Wednesday through Thursday night.

- Cooler temperatures and precipitation chances extend to the rest of the area Thursday and Friday.

DISCUSSION

Issued at 427 AM MDT Tue Apr 21 2026

Temperatures will reach their peak of this warm stretch today as the ridge continues its progression over the region. 700mb temperatures of 8 to 10 C will allow for highs to rise into the 70s west of the Divide and 80s east. Along with this, yet another day of elevated to critical fire weather conditions is expected. The difference today will be an uptick of moisture arriving from the southwest, as well an increasing upper level jet. This should be just enough support for isolated convection across western Wyoming, moving from south to north this afternoon and evening. Given the still dry surface conditions (T/Td spread of 40 to 50 degrees), strong outflow wind gusts appear likely with this activity, though it should be pretty isolated.

The upper low will approach Wyoming tonight, with the accompanying cold front moving west to east across the area beginning Wednesday morning. Ahead of the front, southwesterly wind will ramp up as a strong surface low develops to our northeast. This will be supported further by an encroaching 100 knot upper jet. With a still dry boundary layer, this will lead to at least a few hours of widespread critical fire weather conditions beginning late Wednesday morning. The question will be how long these conditions will last before the front passes and humidity increases. Regardless, wind of 40 to 55 mph will certainly support quick fire spread with any new starts, and a Fire Weather Watch is now in place for locations that have critical fuels. There is also a 50 to 60 percent chance of a couple of hours of wind gusts reaching high wind criteria (at least 58 mph) just ahead of the front, especially across the Wind Corridor from Rock Springs to Casper.

Meanwhile, rain and mountain snow will start across western Wyoming by late Wednesday morning. Initial westerly midlevel flow and a steady stream of moisture up the Snake River Plain will support decent snow rates across the mountains, most notably the Tetons which could see a quick 6 to 12 inches through Wednesday night. Accounting for additional snow expected on Thursday, a Winter Weather Advisory is now in effect for the Tetons and the rest of the western mountains. Snow levels will drop to the western valley floors Wednesday evening, though accumulations are mostly expected to be under 2 inches.

Rain and mountain snow will spread east of the Divide Wednesday night through Thursday. Unfortunately for those of us wanting a drought busting precipitation event, the main low with this system is still expected to pass to our north, displacing the best moisture into Montana. Northern Wyoming will accordingly be most favored on Thursday, as well as the far western mountains that will benefit from favorable orographic flow. However, there will be a second chance, at least for those east of the Continental Divide: while this first midlevel low will move away on Thursday, another one will follow quickly Thursday evening. This will bring additional precipitation chances through Friday. The caveat with this is a familiar one; moisture content is looking fairly low, and forecast accumulations are generally only a tenth or two east of the Divide, with little to none across southwestern Wyoming. With snow levels dropping to the basin floors Thursday night, some of this may fall as snow east of the Divide.

Further out, ensemble cluster guidance continues to support lower 500 mb heights through the weekend. This would favor cooler temperatures and additional chances for precipitation, perhaps even into next week.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 503 AM MDT Tue Apr 21 2026

VFR flight conditions are forecast through at least 12Z Wednesday. Winds remain 10 kts or less through 15Z at KCPR and 18Z to 21Z at all other terminals. After these times, winds increase with frequent gusts between 20kts and 25kts. KRKS will see the strongest winds with gusts up to 30kts possible. Gusty winds largely subside between 00Z and 02Z, except at KRKS where gusts persist into the overnight hours. At KRIW and KLND there is a 20 to 30 percent chance that gusty winds could persist through 12Z Wednesday. Otherwise, expect mid to high level clouds throughout the TAF period.

There exists a 15 percent chance of a shower or thunderstorm across western Wyoming (near KJAC, COD, KPNA, and KBPI) between 23Z Tuesday and 05Z Wednesday. Any showers or thunderstorms that develop will be isolated in nature and because confidence is low in direct impacts, there is no mention in TAF at this time. However, a nearby shower or thunderstorm could produce gusty 30 to 40 mph outflows.

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 427 AM MDT Tue Apr 21 2026

Warm, dry, and breezy conditions will continue to support near- critical fire weather conditions today for much of the area. Wind will again be the question mark on if and where conditions can reach critical criteria. Wind will not be a question mark on Wednesday. Strong southwesterly gusts of 40 to 55 mph will be widespread as a cold front approaches from the west. This will support critical fire weather conditions before humidity values increase behind the front. Cooler and wetter conditions are then expected Thursday into the weekend, though breezy conditions will persist across the area.

RIW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from noon Wednesday to 11 PM MDT Thursday for WYZ001-012-024.

Fire Weather Watch from Wednesday morning through Wednesday evening for WYZ275-276-280>283-285-287-289-300.