


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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972 FXUS65 KRIW 070455 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1055 PM MDT Sun Jul 6 2025 .KEY MESSAGES... - Warmer temperatures Monday through Wednesday with an increasing chance for elevated fire weather conditions due to gusty southwest wind and low relative humidity. - Very hot conditions with widespread 90s and some locations getting close to the triple digit mark Tuesday and Wednesday. The lowest elevations of the Bighorn and Wind River Basins have a 30-50 percent chance of 100 degree highs Wednesday. - A 20-40 percent chance of thunderstorms returns Thursday afternoon and evening, especially along and east of the Continental Divide. && .UPDATE... Issued at 1216 PM MDT Sun Jul 6 2025 No major updates to the forecast with the afternoon update. Hi-res models continue to depict virga or weak storms forming across Sweetwater, Natrona, and Johnson Counties for the latter half of the afternoon through the evening. Any of these could produce a 50 to 55 mph outflow gust; these gusts would be more likely in Sweetwater County, (generally along and south of I-80) where drier air is in place. Showers/storms linger longest around Johnson County, and should be done around midnight. Some models do keep reflectivity in a little longer. && .DISCUSSION... Issued at 120 AM MDT Sun Jul 6 2025 Isolated showers have gradually ended over eastern portions of the CWA this morning. Mostly clear skies are in place elsewhere away from this activity. There is a low chance (20%) for low clouds to develop around Casper between 10Z-14Z. One of the aspects against this will be sfc winds turning to the west-southwest after sunrise. The passage of Saturday`s shortwave will mark the end of the latest active weather pattern, as drier air moves into the region. Flat ridging will be in place today, with the front from Saturday night washing out through the day and keeping daytime temperatures similar to Saturday. Conditions will be mostly dry across the area today, with Casper being an exception once again. A shower and/or thunderstorm looks possible between 22Z-01Z over southern Natrona County, including the Casper area and Casper Mountain. Wind gusts up to 55 mph and small hail would be the likely threats. Isolated virga showers will also be possible over southern portions of Sweetwater County, with wind gusts up to 55 mph also possible. Otherwise, the focus will shift to fire weather for the first half of this week, as an upper level ridge builds over the region from a strengthening high center over the Four Corners. Winds look to remain light through Wednesday with mostly dry conditions. A weak, shallow back door cold front will push through Natrona County and the Wind River and Bighorn Basins after sunset Monday evening, turning winds easterly in its wake. The front will stall and wash out by sunrise Tuesday morning. The warming trend will continue Tuesday, with 90 degree temperatures returning for areas east of the Divide as well as across portions of Sweetwater County. Several locations east of the Divide could reach 100 degrees Wednesday, including Greybull, Worland, Thermopolis, Casper and Riverton. The GFS extended MOS guidance is forecasting 100 degrees at Riverton and Greybull. The next chance for precipitation looks to occur Thursday, as a trough digs southward from Canada over MT. The previously discussed remnant low will speed up and reach the Cowboy State Thursday morning and eventually get absorbed by the incoming trough. This could result in isolated showers early Thursday morning. This trough would lower temperatures a bit and cause the high to retreat further south. Moisture return looks to be confined over northern portions at this time, with Johnson County having the best chances for precipitation. Additionally, strong northwest winds could hit northern Johnson County, including Buffalo, in the wake of the cold front associated with the trough. No strong wind signatures are evident yet, but gusts of 50 to 60 mph could occur as this would be common with these kinds of fronts. There could also be a significant reduction in temperatures Friday morning as a result of this front. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1055 PM MDT Sun Jul 6 2025 Terminals to be VFR through 06Z/Tuesday as drier air aloft punches farther east across the forecast area. Several outflow boundaries and weak instability have allowed for lingering convection late Sunday evening, which should end by 08Z/Monday. KCPR would be the most likely terminal to see outflow or a brief sprinkle. Convection that reignites Monday afternoon and early evening will be confined to areas around and east of a KBYG-KCPR line. Also, weak convection occurs south of KRKS where showers and storms move east-northeast off the Uinta Mountains. Otherwise, shower and thunderstorm chances are less than 10 percent. Afternoon westerly wind 10-15kts will be common at terminals west of the Continental Divide until 02Z/Tuesday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Wittmann DISCUSSION...LaVoie AVIATION...CNJ