textproduct: Western and Central Wyoming

KEY MESSAGES

- Above average temperatures continue today and Thursday ahead of the next storm system.

- Increasing rain chances Thursday morning and throughout the day with mountain snow likely for western mountains later in the afternoon and overnight into Friday, spreading to eastern mountains Friday evening.

- Wind ramps up starting Thursday, strongest Friday east of the Divide and across the wind corridor with gusts ranging from 40 to 55 mph (80-90% confidence). This will also lead to elevated fire weather concerns east of the Divide.

- A cold front pushes through Friday morning, bringing cooler temperatures to near seasonable heading into the weekend as well, reinforcing snow chances lowering to 8-9kft to impact mountain passes for Friday evening and Saturday morning.

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 /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1125 AM MDT Wed Oct 21 2026

VFR flight conditions are largely forecast through 18Z Thursday. There is a 10% to 20% chance of a rain shower at or around KJAC, KRKS, and KCPR between 23Z Wednesday and 08Z Thursday, at the latest. Given the low confidence in occurrence and impacts, there is no mention in TAF at this time. There is also a 10% to 25% 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 added a FEW or SCT cloud group at 025 or 035 at this time. Breezy winds are forecast at KRKS and KCOD this afternoon, KRIW and KLND after sunset, and at KCPR after sunset Thursday morning. Winds remain relatively light at all other terminals.

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.