941 FXUS65 KRIW 260855 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 255 AM MDT Sat Jul 26 2025 .KEY MESSAGES... - Elevated to critical fire weather is likely today along isolated afternoon showers and thunderstorms. - Hot and dry weather will continue through Monday. - A transition to a cooler and wetter pattern begins Tuesday and continues through at least Thursday. && .DISCUSSION... Issued at 252 AM MDT Sat Jul 26 2025 Climatologically, we are in the hottest time of the year. And the next few days are no exception. Ridging will control the weather over the Cowboy state and bring hot temperatures to much of the area. Not record breaking heat, but highs in the 90s will be fairly widespread in the lower elevations East of the Divide with 80s in the lower elevations to the west. However, temperatures are not the main concern of the forecast, fire weather is. All in all, today looks to be main day of concern. A weak shortwave will move across the state today, helping to enhance mixing any with 700 millibar winds anywhere from 20 to 30 knots expected to mix to the surface, critical fire weather looks likely. This will be mainly in the southwestern Wind Corridor from Rock Springs through Casper where the chance of 3 hours of wind gusts past 25 mph is greater than 3 out of 5. So, we upgraded the Fire Weather Watches to warnings. We also gave thought to adding Zone 283, which could see gusty wind this afternoon. The chance here is only 1 out of 3 though, so we decided not to. Elsewhere, elevated fire weather is likely given that humidity will be very low, with most areas under 15 percent and many areas under 10 percent. There is another concern though. The shortwave could touch of some isolated showers and thunderstorms this afternoon. Given the lack of moisture, these would all be high based and the chance at any point is less than 1 out of 5. These are also impossible to pinpoint. So, we left continuity alone. Many of these would not have any rain, only virga/ However, given the high bases of the convection and very large dew point depressions, (over 60 degrees in many locations), any thunderstorms, shower or even enhanced cumulus cloud could produce strong wind gusts if it collapses. The next question is, what about fire weather for tomorrow. It looks more borderline. For one, there will be no shortwave to mix the atmosphere and 700 millibar winds are 5 to 10 knots lighter. This is especially the case in Natrona and Fremont Counties. For now, we kept the warning for today but we may end up extending it out through Sunday. This would be mainly for Sweetwater County though. We will let the day shift or Saturday`s night shift take another look at it before issuing. And with no shortwave, the chance of convection will be near zero for most locations. The only place would be the northern mountains but even here the chance is less than 1 out of 6. Monday at this point looks like another hot and dry day, with the same chance of isolated storms across the far north. Wind looks lighter on this day though, so the chance of critical fire weather looks low (less than a 1 out of 4 chance) despite humidity remaining low. This changes on Tuesday though. A cold front will slide toward the area from the north. At the same time, a surge on monsoonal moisture moves in from the south and east. The result will be a much more moist atmosphere. Precipitable waters will jump from 30 percent below normal to 150 percent above normal for areas East of the Divide on Tuesday and most areas on Wednesday. And the result will be more cloud cover, cooler temperatures, and an increased chance of showers and thunderstorms through at least Thursday. At this point, Wednesday looks to be the day of the most widespread showers and storms. Pinpointing areas of the heaviest precipitation, especially with convection, is very difficult this far out though. However, confidence is high (around a 4 in 5 chance) that will will transition into a wetter pattern starting on Tuesday. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1020 PM MDT Fri Jul 25 2025 Clouds will begin to increase from the southwest through 12Z, with SCT-OVC FL150-250 being in place across areas west of the Divide after sunrise and spread to the northeast through the rest of the morning. Virga showers and dry thunderstorms will become possible from these clouds between 18Z and 00Z. Confidence remains too low to include in any terminal forecast, except KCOD, for now. However, most of the convective activity will be moving over areas close to KBPI/KPNA, KLND/KRIW, KWRL and KCOD. Gusty winds will increase again around 18Z, with gusts reaching around 25 kts. Most of these showers will not be reaching the ground, but may produce some locally stronger gusts as they pass. The convective activity is expected to end and/or wane around sunset. 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 252 AM MDT Sat Jul 26 2025 A combination of humidity falling into the single digits and a gusty afternoon breeze will bring critical fire weather to southern Lincoln, Sweetwater, southeastern Fremont and Natrona Counties this afternoon. Elevated fire weather is likely for other locations. Elevated to possible critical fire weather continues on Sunday with some easing of conditions on Monday and especially the middle of next week. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from noon today to 8 PM MDT this evening for WYZ277-279-280-289. && $$ DISCUSSION...Hattings AVIATION...LaVoie FIRE WEATHER...Hattings