textproduct: Western and Central Wyoming

KEY MESSAGES

- A windy day is expected today with widespread 30 to 55 mph southwesterly wind gusts. Wind prone locations could see wind gusts above 60 mph (50-80%).

- A Red Flag Warning is in effect for all areas east of the Divide today. Should a fire start, rapid fire spread and erratic fire behavior is expected due to the strong winds.

- Western mountain snow and western valley rain and snow is forecast to begin late this morning and continue through late Thursday. Winter travel conditions are expected across all western mountain passes due to snow and wind.

- A cooler, more active weather pattern is favored Friday through the upcoming weekend.

DISCUSSION

Issued at 323 AM MDT Wed Apr 22 2026

Satellite water vapor imagery at 09Z/3AM shows an upper level low circulating over northern California/Nevada with southwesterly flow over Wyoming. An associated surface low is located over northeast Idaho with a cold front over western Utah. This system will be our "weather maker" as it ejects into Montana today, bringing critical fire weather conditions, widespread wind, and precipitation chances.

The pressure and temperature gradient will tighten through the day today as the cold front approaches from the west. Additionally, an 80kt to 100kt upper level jet will be present across the Wind Corridor as the low shifts into Montana. This will result in widespread strong and gusty southwest winds a majority of the day. Southwest winds will quickly ramp up between 9AM and 10AM this morning as deep mixing begins. Widespread wind gusts of 30 to 50 mph can be expected (90%+ chance) across most low elevations. Wind prone locations could see occasional gusts of 60 mph or greater, especially in the hour or two ahead of the frontal passage. There are some indications of a mountain wave breaking over the eastern slopes of the Wind River Mountains in the morning to early afternoon hours. Should this occur, wind gusts of 50 to 70 mph are possible across the eastern slopes of the Wind River Mountains and potentially making it around Lander and Fort Washakie. The cold front is forecast to traverse the state between 2PM and 6PM today, with wind gusts remaining in the 30 to 40 mph range for a few hours behind the front due to the temperature gradient.

The strong and gusty winds mentioned above in combination with dry air ahead of the cold front will create critical fire weather conditions for all areas east of the Divide. Minimum relative humidity values are forecast to be in the 10 to 13 percent range this afternoon. A Red Flag Warning is now in effect from 9AM to 8PM today. Behind the cold front, relative humidities are forecast to increase to a 15 to 25 percent range through sunset. The expected strong winds behind the front will keep conditions favorable for erratic fire behavior despite minimum relative humidities likely being above Red Flag Criteria (15 percent or less) from 5PM to 8PM.

The final component of this weather system will be the precipitation chances along and behind the cold front. Because of the Pacific origin of the system, there will enough available moisture to bring accumulating mountain snow and low elevation rain and snow to the west. Through late Thursday night, there is an 80 to 95 percent chance of at least 8 inches of snow for elevations above 7,500 feet across the western mountains. Chances of 12 inches or more are in the 40 to 70 percent range and confined to the Tetons. Gusty winds of 30 to 50 mph will also be common. Given the slightly lower confidence in widespread 12 inches or more of snow and the higher sun angle, opted to maintain the Winter Weather Advisory. The Absaroka Mountains have been added to the Winter Weather Advisory with an 80 to 90 percent chance of snow accumulations of 6 inches or more and gusty 50 to 70 mph winds. Winter travel conditions are expected with the snow and gusty winds across all western mountain passes. There will also be enough instability (up to 500 J/kg of CAPE) to support some instances of thundersnow. As for Jackson Valley and Star Valley, precipitation will remain as rain most of the daylight hours today before changing over to snow after sunset when snow levels drop below 6,000 feet.

Precipitation will largely be focused across the west today through at least mid-day Thursday due to the low passing north of Wyoming. On Thursday afternoon, a shortwave is forecast to drop down from Canada and provide support for another front to traverse the state. This front is forecast to bring cooler temperatures and precipitation. Precipitation will finally push east of the Divide late Thursday through most of Friday, first as rain across low elevations. Rain will quickly change over to snow overnight Thursday into Friday with 700 mb temperatures behind the front being in the minus 6 Celsius to minus 10 Celsius range. However, snow amounts are forecast to be minimal by Friday night with less than a 40 percent chance of 2 inches of snow for the basins.

By Saturday, the above normal temperatures that we have been experiencing will be a thing of the past. Lower 500mb heights are forecast across Wyoming Saturday as the previously mentioned upper level low sits itself over southern Canada. By late Saturday, ensemble guidance is in consensus that an associated longwave trough will develop over the western CONUS with embedded passing shortwaves. There are also indications that upper level troughing and embedded shortwaves, will keep an almost constant fetch of moisture into the Northern Rockies. If this comes to fruition, a more active period of more widespread precipitation is favored late Saturday into early next week.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 430 AM MDT Wed Apr 22 2026

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

VFR conditions to start the period as winds increase starting after around 15Z. Highest winds during peak heating of the afternoon ahead of FROPA, up to 30kts at JAC, 35kts at BPI/PNA, and up to 40kts at RKS. These winds will slowly diminish some but remain elevated after sunset around 03Z, highest at RKS but down to around 10-15kts at all other locations after 10-11Z. Shower activity increases around 18-19Z at all but RKS due to the shortwave more north not affecting further south. Thunderstorm chances with enough instability during the afternoon with PROB30 groups diminishing after 04Z outside of JAC even through the overnight hours. The next round will be into the next TAF cycle for Thursday afternoon. MVFR conditions may exist with storm/shower activity on station with mountain obscuration evident for much of the afternoon/evening timeframe.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

VFR conditions with no precipitation expected until the next TAF cycle for Thursday afternoon. The main threat will be wind increasing after 16Z ahead of FROPA. Highest wind speeds at CPR/RIW up to 40kts, 35kts at COD/LND/WRL. These winds will diminish some after 03Z about 10-15kts less than the peak heating of the afternoon. Mountain obscuration likely for the Winds/ Absarokas with the winter weather west of the Divide but increasing in coverage going into the next TAF cycle for Thursday afternoon and beyond.

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 323 AM MDT Wed Apr 22 2026

Warm, dry, and windy weather will cause critical fire weather conditions east of the Divide today ahead of an approaching cold front. East of the Divide and ahead of the cold front, relative humidity values are forecast to be in the 10 to 15 percent range with widespread southwesterly gusts of 35 to 55 mph. Occasional gusts of 60 mph or greater are possible, especially for wind prone locations. The cold front is forecast to trek across the area between 2PM and 6PM today, with relative humidity to be in the 15 to 25 percent range behind the front. Winds will remain gusty through sunset. Elevated fire weather conditions are expected across southern Wyoming today as well. Should a fire start, especially ahead of the cold front, erratic fire behavior and rapid fire spread is expected.

RIW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from noon today to 11 PM MDT Thursday for WYZ001-002-012-024.

Red Flag Warning from 9 AM this morning to 8 PM MDT this evening for WYZ275-276-280>283-285-287-289-300.