538 FXUS65 KRIW 060852 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 252 AM MDT Sat Jun 6 2026 .KEY MESSAGES... - Warmest day of the year today, with most areas soaring into the upper 80s to upper 90s. YNP will reach the low to mid 70s. - Very dry and very windy conditions across most of the state today will lead to elevated to critical fire weather concerns. Most lower elevations will see humidity fall to 8 to 10% and wind gusts well above 30 mph through the afternoon. - The next in a series of weather systems moves into western WY tonight, bringing showers tonight to the western mountains, before moving east into central WY on Sunday. && .DISCUSSION... Issued at 206 AM MDT Sat Jun 6 2026 The long-awaited buckling of the midlevel flow has begun to strengthen across the western US, and will bring the warmest day of 2026 to most of the state. H7 temperatures are already running 12-14C, and will be peaking this afternoon between 16 and 18C, which translates to the sfc as highs in the upper 80s to the upper 90s. Isolated readings at 100 degrees may be noted along the lowest elevations of the Bighorn Basin for a few hours this afternoon. Temperatures aloft will be cooler for NW WY, which is closer to the incoming trough, which will keep temps more modest in the 70s this afternoon. The southwest flow around the approaching trough will be very dry, and with dry air already at the sfc, will mix well down to the sfc this afternoon. Wind gusts will reach 35 to 50 mph through the afternoon, picking up around noon and continuing into the early evening. Humidity levels will also crash down this afternoon, staying below 10 percent through the afternoon. This leads to critical fire weather concerns all day. Tonight, the advancing trough moves off the PacNW coast into the Northern Rockies, pushing the heat ridge eastward and opening up most of the state for increased moisture. There is a hint in some of the convective models that today's heating may be enough to tap the leading edge of the trough to spark a few showers even into central WY this afternoon, but this will be battling against the subsidence with the ridge, so this area may be limited to some increased CU. The better chances for showers first builds into the NW Parks this evening and overnight as the first lobe of the trough passes through. The next band then sets up somewhere in central WY during Sunday afternoon, influenced by an instability axis aloft. As the trough moves east, an enhanced area of shear builds into northern WY, which will also be influenced by terrain shear off the Bighorn Range. Strongly sheared environment and instability could lead to thunderstorms quickly strengthening across Johnson County during the afternoon, with a quickly increasing threat for hail and very strong winds. SPC has this areas in a slight risk on Sunday, and will need to monitor for final timing. Into early next week, the main trough shifts east, putting the axis along the Rockies for the first half of the week. Right now, this puts the northern half of the state in a more showery pattern through most of the upcoming week. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1029 PM MDT Fri Jun 5 2026 VFR conditions will be in place through the TAF period. Clouds will increase from the west-southwest, with SCT-BKN FL150-250 skies in place over western portions by 12Z. these clouds will then spread east of the Divide, becoming FEW-SCT by 18Z. Any convection Saturday afternoon will be very isolated, with KJAC and KCOD having the best chances. With that said, chances remain too low to include in a PROB30 group at this time. There is a chance for showers/thunderstorms to pass over KJAC at times between 00Z and 06Z, but again confidence remains too low to include in the forecast at this time. Wind gusts of 20 to 30kt will return between 17Z and 19Z for all terminals, decreasing again around 01Z/02Z with light winds (11kt or less) returning through the end of the forecast period. 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... Red Flag Warning from 11 AM this morning to 8 PM MDT this evening for WYZ280. && $$ DISCUSSION...Straub AVIATION...McDonald/LaVoie