


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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495 FXUS65 KRIW 091041 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 441 AM MDT Wed Jul 9 2025 .KEY MESSAGES... - Very hot conditions with widespread 90s and some locations getting close to the triple digit mark today. The lowest elevations of the Bighorn and Wind River Basins have a 40-70 percent chance of reaching 100 degrees. - Elevated fire weather conditions continue today as well. Humidity will be very low, but wind gusts will be limited through the afternoon. - Isolated virga showers will again be possible. Wind gusts of 55 to 60 mph will be the main threat from any shower that forms. - Another round of showers is possible for southern and western WY tonight. Some of these could reach areas east of the Divide Thursday morning. Overall chances of any accumulation remain low. && .DISCUSSION... Issued at 157 AM MDT Wed Jul 9 2025 The anticipated hottest day of the week has finally arrived. The ridge that has been in place since Monday will continue its eastward shift eastward this morning over the Cowboy State. 700mb temperatures will be slightly higher today, ranging between 16C to 19C. 90 degree temperatures will be widespread once again, with portions of the Bighorn Basin approaching 100 degrees. Winds continue to look marginal for any fire weather highlights, however gusts over 25 mph will occur at times (between 21Z and 00Z) over areas with critical fuels. The atmosphere should be capped for most areas, however isolated virga showers will be possible again in the afternoon into the evening. Sweetwater County continues to look the most likely location at this time, due a lead shortwave that will move over the county from northern UT. Chances for these showers will begin to increase after 21Z and move out of the area through 06Z Thursday. Wind gusts of 55 to 60 mph will again be possible, due to the inverted-V sounding profiles in place. A remnant low will approach the area through the overnight hours Wednesday night, as it moves over southern ID. The aforementioned lead shortwave will be ahead of this system. Increasing chances for showers and isolated thunderstorms will become possible over western portions after 06Z. Lightning chances are low, due to a lack of moisture that is reflected in CAPE values of 100-200 J/kg. These chances for precip quickly spread east of the Divide by 09Z, heading to the east-northeast. Precipitation chances associated with this wave will exit Johnson County after 15Z, with additional showers possible over Johnson and Natrona counties through the afternoon. Little to no rain is expected from this activity today and Thursday, due to a lack of moisture. Temperatures will be about 10 degrees cooler across the CWA Thursday as a result of the passage of this remnant low lowering heights and suppressing the Four Corners high to the south (the high will retrograde over the Desert Southwest at the same time). Fire weather conditions will remain elevated as well, but critical RH values will be isolated and confined to Sweetwater County. As expected, the timing from the trough dropping south from Canada has slowed down and now looks to reach the MT/WY border Friday morning. Any precipitation looks to be confined to northern portions through the day Friday. Highs in the 70s east of the Divide is still in the forecast, while areas west of the Divide stay in the low to middle 80s. Dry conditions then return for the weekend, with seasonal temperatures on Saturday and highs in the 90s return for areas east of the Divide on Sunday. Showers and thunderstorms could be possible over far northern portions Monday afternoon, as another trough drops south from Canada/British Columbia. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 428 AM MDT Wed Jul 9 2025 Mainly VFR conditions throughout the period for all TAF sites. Winds and upper level clouds will increase for all locations after 18Z to 20Z with daytime heating and mixing to the surface. Most locations will gust up to 18 knots with KRKS the highest, peaking close to 25 knots. Any shower activity will be limited and not expected on station, but KRKS will have the only real shot from a stray one and random stronger gust of wind in the late afternoon/evening. The chance is less than 1 out of 6 though so we will not include in the TAFs at this time. Winds will diminish after 01Z-02Z with nighttime cooling once again. However, a couple models are indicating a stronger wind gusting up to 30 plus knots at KLND after 03Z that are of higher reliability. An approaching area of low pressure will bring the chance of showers (about 1 in 4 to 1 in 3) to KRKS, KBPI and KPNA after 05Z tonight. A few showers may spread East of the Divide after 08Z but less confidence here. With the chance of thunder, we have gone with a PROB30 group for KRKS, KBPI and KPNA. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .FIRE WEATHER... Issued at 157 AM MDT Wed Jul 9 2025 Widespread elevated fire weather conditions continue as temperatures remain hot critical RHs spread with values of 6 to 15 occurring across the area. Gusty winds will increase this afternoon, with frequent gusts reaching 20 mph, with higher gusts in the higher elevations. Red Flag Warnings continue to look marginal due to gusty winds above 25 mph being isolated over critical zones. Gusts of 25 to 35 mph will occur over zones 140 and 286 through the afternoon. Isolated virga showers will remain possible this afternoon, with zone 279 having the best chances. Gusts of 55 to 60 mph could occur with the showers. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...LaVoie AVIATION...Hattings FIRE WEATHER...LaVoie