textproduct: Western and Central Wyoming

KEY MESSAGES

- Periods of moderate snow, and occasional instances of thunder, are expected across the western mountains, Yellowstone National Park, and the Bighorn Mountains today. Snow or a rain/snow mix is expected for the western Valleys. Winter travel conditions are anticipated across mountain passes.

- Elevated fire weather conditions exist early this afternoon across portions of central Wyoming. Precipitation chances (60 to 90 percent) increase late this afternoon and overnight across low elevations east of the Divide.

- A cooler, and overall more active weather pattern is favored Friday through early next week.

DISCUSSION

Issued at 254 AM MDT Thu Apr 23 2026

The upper level low that brought precipitation to western Wyoming and widespread wind on Wednesday is now (09Z/3AM) positioned over northeastern Montana. A shortwave rounding this low will traverse the state and provide support for periods of moderate snow across the western mountains, Yellowstone National Park, and the Bighorn Mountains through roughly 11 AM this morning. In addition to the snow, widespread wind can be expected. For lower elevations wind gusts this morning will generally be in the 20 to 35 mph range with the shortwave passage. Higher elevations and wind prone locations have a 60 to 75 percent chance of at least 40 mph winds this morning.

The next "round" of snow, wind, and colder temperatures will arrive shortly after the aforementioned shortwave moves through. Another upper level low, currently over the Canadian province of Alberta, will shift south and "absorb" the current Montana low early this afternoon. As it does so, a shortwave and associated cold front will move south into Wyoming. The cold front is currently forecast to move north to south across the state between 3PM and 9PM today. As it drops south, another round of moderate snow is expected for the western mountains, Yellowstone National Park, and the Bighorn Mountains. The Bighorn Mountains have been added to the Winter Weather Advisory today for snow amounts of 5 to 12 inches through 11PM tonight. There is generally a 60 to 90 percent chance of at least 6 more inches of snow across the western mountains and southwest portions of Yellowstone National Park today, so the Winter Weather Advisory remains in effect. Winter travel conditions can be expected with snow and wind for all western mountains passes and Powder River Pass. There will be some instability (around 200 J/kg, unstable mid level lapse rates, and increased frontogenesis) with the front this afternoon/evening, so some instances of snow banding and thundersnow is possible.

This cold front also brings some precipitation potential and more wind to most low elevations of central and western Wyoming. First, the pressure gradient will continue to tighten early this afternoon bring widespread 25 to 35 mph winds, with wind prone locations seeing occasional gusts of 50 mph. For the Wind River Basin and Natrona County specifically, the boundary layer remains relatively unsaturated ahead of the front. The wind and dry air (relative humidity around 20 percent) across these areas, will create elevated fire weather conditions early this afternoon. Relative humidity is forecast to be between 25 and 30 percent elsewhere. Additionally, ahead of the front, isolated showers and/or virga and thunderstorms are possible (30 percent) across central Wyoming. There will be moisture accompanying the cold front so there exists a 60 to 90 percent chance of precipitation for all areas east of the Divide and across western Wyoming. For areas east of the Divide, expect precipitation to start first as rain. Because of the Canadian origin of the system, a cold push of air is expected behind the front which will allow for rain to change over to snow late tonight and continue as snow overnight. Most low elevations east of the Divide have a 40 to 80 percent chance of seeing 1 inch of snow by Friday morning. Areas such as northern Natrona County and Johnson County have a 60 to 70 percent chance of seeing 2 inches of snow by Friday morning. The front ultimately stalls along the northern Sweetwater County border, so southern Wyoming can expect to remain dry.

The front will remain stalled roughly along the northern Sweetwater County border on Friday. In the upper levels, the low stalls over the southern Canadian Provence of Saskatchewan with zonal flow, and embedded passing shortwaves over Wyoming. With 700mb temperatures of minus 2 Celsius to minus 10 Celsius, a cool day with light snow or a rain/snow mix can be expected north of the front. South of front across southern Wyoming, a relatively warm, dry, and windy day is forecast on Friday. Southern Wyoming will be windy due to passing shortwaves aloft and a tight gradient at the surface. Should the front stall farther to the south, southern Wyoming could see some precipitation but the current chances of this occurring are 15 percent.

The front lifts north on Saturday as the upper level low's trough expands to the west and puts Wyoming in more west to southwest flow aloft. Expect Saturday to be the drier and warmer day of the weekend as a brief push of drier air moves in. However, this drier air will not last for long. Ensemble guidance is in consensus that by later Saturday a shortwave trough embedded in the southwesterly flow will approach southern Wyoming and usher Pacific Moisture into the Intermountain West. By Sunday, there are indications that an associated 700mb low will traverse the across the Wind Corridor region of the state. This is currently not looking to be a major precipitation event by any means. There are still plenty of uncertainties with regards to the exact location, timing, precipitation amounts, and temperatures with this system. However, if this trend continues, many areas could see precipitation on Sunday. Ensemble guidance has a reasonable about of agreement that more zonal flow will set up over the state with weak embedded disturbances Monday through Wednesday. This indicates that there are more precipitation chances on the horizon for Wyoming next week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 500 AM MDT Thu Apr 23 2026

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

MVFR conditions at JAC/BPI/PNA to start the period with light snow on and off at these locations. Winds have diminished outside of a low gust up to 18kts at RKS. Otherwise, winds increase after 13-16Z, highest at RKS up to 35kts expected with other locations up to around 25kts. Best chances for snow showers this afternoon after 20-21Z for all but RKS being further north the main shortwave. Improving conditions after 04-06Z as winds diminish there after into Friday morning. IFR conditions not expected but something to keep an eye on during period of snowfall this afternoon and early evening. Mountain obscuration expected for the Winds/Tetons/Gros Ventres with improvement overnight as the snow pushes east and conditions improve.

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

VFR conditions to start the period with light winds. Winds increase after 16-17Z with the next FROPA as rain shower activity increases behind it around 20-21Z. Turnover to snow possible after 02-03Z with the colder temperatures behind the cold front but winds will diminish after this point to around 10-12kts or less. MVFR conditions expected with shower activity but improving conditions for most after 06Z with lingering snow likely at CPR with possible IFR conditions due to the stronger wind intact further east as per usual for the wind corridor. VFR and lighter winds expected into the next TAF cycle for later Friday morning and afternoon. Mountain obscuration expected widespread through much of Thursday and especially overnight and to include the Bighorns.

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

RIW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 11 PM MDT this evening for WYZ001-002-008-009-012-024.