textproduct: Western and Central Wyoming

KEY MESSAGES

- A few showers are expected across the western mountains this afternoon and evening. Otherwise, above average temperatures continue for most locations through Thursday.

- Precipitation chances increase Thursday as a system begins to move into the area. This will bring rain and mountain snowfall to the area through Friday, mostly along and west of the Continental Divide.

- Strong wind gusts of 40 to 55 mph are expected on Friday along the Wind Corridor from Sweetwater County through Johnson County. This will lead to near-critical fire weather conditions Friday afternoon.

- Much cooler temperatures are expected this weekend behind the incoming system.

UPDATE

Issued at 315 PM MDT Wed Oct 21 2026

A few showers have popped up over the western Wyoming mountains this afternoon as moisture and upper level lift increase with the incoming system. Mountain snow accumulation continues to decrease with the latest guidance. This is due to both decreasing liquid precipitation and the fact that the system is relatively warm; snow levels will mostly remain above 8,500 ft. East of the Divide, the more notable concern with this system will be fire weather as winds come up on Friday ahead of the cold front. While humidity is expected to remain above 20 percent, sustained winds of 25 to 35 mph with gusts nearing 50 mph will lead to near critical fire weather conditions.

DISCUSSION

Issued at 130 AM MDT Wed Oct 21 2026

IR currently depicts mid level clouds pushing in across western and northern parts of the CWA from the southwest, extending from Baja Californian moisture extending through the Four Corner Region. WV imagery shows the main finger of the PFJ extending across southern Canada and a strong upper level low off the central Californian coastline. This low will begin its eastern extent Wednesday night into Thursday as it becomes a more open and progressive wave that will strengthen the southwest and divergent flow into the CWA out of northern Utah. This is where the stronger PVA anomalies will occur extending moisture content into southern portions of the state by Thursday morning.

The aforementioned PFJ will start to dip across the Pacific northwest aligned with the main low as it becomes more open late Thursday with an increasing jet max pushing 120-130kts. This deepens the northern portions of this system with increased divergence aloft. This increases the pressure gradient across much of the CWA about 5 to 7 mb across the state, strongest across the south. Southwest winds push 40 to 55 mph Thursday afternoon during peak heating and mixing to the surface, strongest across the wind corridor from Sweetwater through eastern Fremont to Natrona Counties. Occasional gusts over 60 to 65 mph possible (40-50%) for the higher terrain areas of South Pass and outer drive of Casper Mountain. There is low confidence on high wind criteria being met for this period of time, but winds remain elevated overnight into Friday morning with wind shifts occur due to a passing cold front extending through the CWA into the afternoon hours Friday.

Precipitation wise, expect shower activity to increase out of northern Utah into southern portions of the CWA Thursday morning pushing north throughout the day. Much of the QPF will fall west of the Divide with some higher terrain mountain snow expected by late Thursday afternoon and especially overnight as temperatures fall. This will be reinforced with FROPA on Friday, lowering freezing levels to 8-9kft as the system shifts east of the Divide, and thus, impacting the Bighorns with mountain snow. Mountain passes, to include Teton, Togwotee, and South Pass, extending to Granite/Powder River, will see the impacts and hazards late Friday and into Saturday morning as the trough shifts northeast by day's end Saturday. Probabilities for snowfall totals look to be of higher confidence across western mountains, to include the Winds, of 6 inches or more around 60-70%. The Bighorns are of lower confidence around 30-40% for later Friday and into the overnight hours. With snowfall totals of not great confidence, and being Friday for impacts, it has been decided to include surrounding offices to not issue any headlines at this time. Model guidance has been up and down the past couple of days with this round bumping totals up once again and will need higher confidence to do so moving forward.

Beyond that, expect more seasonable to just below average temperatures post FROPA Friday and into the weekend to fell more Fall-like for this time of year moving towards the later half of October. Another low extending out of the Gulf of Alaska looks to push down along the L/W pattern into the Pacific northwest late Sunday that will near the CWA early next week. This will not only reinforce this cooler air but continue the active pattern that has a better track for stronger snow totals. Too soon to judge the impacts at this point in time, but this looks to have a better track for higher mountain snow along and west of the Divide. Stay tuned for forecast updates and any headline issuance later Wednesday or Wednesday night as confidence grows for impacts on Friday into Saturday.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 504 PM MDT Wed Oct 21 2026

There is up to a 20% chance of a rain shower at or around KJAC, KRKS, and KCPR through 08Z, at the latest. Given these low chances, there is no mention in TAF at this time. Breezy winds at KRKS and KCOD are expected to diminish by 04Z. At KRIW and KLND, breezy south winds are forecast for a few hours after sunset before diminishing. Elevated winds are forecast at most terminals by 00Z Friday, with gusts of 20 to 25kts expected at KCPR, KRIW, and KLND. There is also a 15% to 30% chance of MVFR clouds or fog at KJAC, KCPR, KRIW, KPNA, KBPI, and KLND early Thursday. The higher chances exist at KCPR, KJAC, KPNA, and KBPI, so maintained the FEW or SCT cloud groups at 025 or 035 at this time.

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.