233 FXUS65 KRIW 202154 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 354 PM MDT Sun Jul 20 2025 .KEY MESSAGES... - Red Flag Warnings are now in effect for portions of southern and central Wyoming from 12 PM to 8 PM Sunday due to low relative humidity and gusty westerly wind. - Elevated to critical fire weather conditions will return across the area Monday, with central portions having the best chances for critical chances. - Virga showers/dry thunderstorms will be confined to Sweetwater County and Yellowstone this afternoon, with widespread chances returning Monday. Chances for afternoon and evening showers and thunderstorms will be in place Tuesday through Friday. && .DISCUSSION... Issued at 146 AM MDT Sun Jul 20 2025 Drier and warmer conditions return today, with elevated to critical fire weather conditions in place for most areas. Will upgrade the Fire Weather Watch to Red Flag Warnings and add zones 277, 282, 283 and 288. Critical RH values, as low as 9 percent, will be widespread across much of the CWA today. West-southwest winds, with gusts of 25 to 30 mph, will develop late this morning and also be widespread in the afternoon. Higher gusts up to 35 mph will occur over the western mountains, especially across Yellowstone and the Absarokas. Big Horn, Washakie and northern Johnson County will have the weakest winds around 20 to 25 mph. Isolated virga showers/dry thunderstorms are still progged over portions of Sweetwater County this afternoon, as well as far northern portions of Yellowstone NP. This convection will end by sunset. Wind gusts of 50 to 60 mph will once again be possible from these passing showers. A closed low will develop over the PACNW from a broad trough over southern Canada during the day Monday. Heights will increase over the Cowboy State as a result, as winds aloft turn more southwesterly. This will lead to a ridge axis to build over the region, extending from a strong high over the Gulf Coast. Hot and dry conditions, with elevated to critical fire weather conditions occurring once again. Critical fire weather conditions look to be confined to central portions. Virga showers and dry thunderstorms will be more widespread Monday afternoon, as upper level divergence increases ahead of the digging upper low, in addition to the proximity of the sfc low and frontal boundary over southern MT and eastern ID. Wind gusts of 50 to 60 mph will continue to be the main threat. The best instability, 200-500 J/kg, will be over northern portions, small hail could be a possibility with the storms in this area. Drier conditions are expected Tuesday, as the aforementioned closed low fills and lifts over MT/southern Canada during the day Tuesday. Convection will be more isolated as a result. Fire weather conditions will remain elevated to near-critical. Another upper low will move over the region Wednesday, with areas east of the Divide looking to have the best chances for precipitation. A ridge will begin to reestablish itself over the region Thursday, as a closed low sits off the northern CA coast. This will allow for Pacific and monsoonal moisture to stream northward and subtle embedded shortwaves to kick off afternoon convection. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 352 PM MDT Sun Jul 20 2025 Very isolated showers and thunderstorms will diminish by 00Z (Monday). There remains low confidence in impacts at KCOD and KRKS during this time. Otherwise, VFR flight conditions are expected to prevail this TAF period with gusty winds diminishing around 01-02Z. Expect winds to remain less than 10kts overnight. Southwesterly winds begin gusting between 17Z-20Z at most terminals with most gusts generally between 20-25kts. KCOD is the exception with winds remaining light. There is a 30% chance in shower and thunderstorm development at KCOD after 20Z Monday. Any showers or thunderstorms could be capable of gusty and erratic winds. This 30% chance is reflected in a PROB30.. All other terminals have a 10%-20% chance for a shower or thunderstorm Monday afternoon so there is no mention in TAF at this time. 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 1230 PM MDT Sun Jul 20 2025 Red flag conditions continue for the afternoon and evening due to low relative humidity values and gusty west winds. Fair to poor recovery overnight for RH as winds diminish as well after sunset. Critical conditions are expected once again Monday afternoon and evening, and thus continuing the RFW then as well for all similar zones except 282 and 287 where RH values will be slightly higher and winds a bit less due to increased moisture further north with a more widespread storm chance off the Absarokas. All other zones not in the RFW will continue to be elevated to near critical. Elevated to near critical fire weather conditions continue for the remainder of the work week with limited isolated storm chances each afternoon and evening. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for WYZ282-287. Red Flag Warning until 8 PM MDT Monday for WYZ277>280-283-288- 289. && $$ DISCUSSION...LaVoie AVIATION...Gerhardt FIRE WEATHER...LaVoie