844 FXUS65 KRIW 261828 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1228 PM MDT Sat Jul 26 2025 .KEY MESSAGES... - Elevated to critical fire weather today, with isolated afternoon showers and thunderstorms. - Hot and dry weather continues through Monday. - A transition to a cooler and wetter pattern begins Tuesday and continues through at least Thursday. && .UPDATE... Issued at 1226 PM MDT Sat Jul 26 2025 Red Flag Warnings continue through 8pm MDT today due to a combination of low RHs and gusty winds. No major changes to the forecast today regarding these weather elements. Have updated the low precipitation chances with latest model guidance. Still expecting mostly virga, with an occasional light shower. Could see a little lightning over northern Wyoming if a stronger cell forms. Main hazard with any convection today continues to be gusty outflow winds. The latest HRRR runs would suggest 30 to 40 mph gusts are most likely, but with the dry air in place, there is potential for stronger gusts. For fire weather tomorrow, winds do not look quite as strong during the afternoon. The one place where 25+ mph wind gusts may occur would be over eastern Sweetwater County (eastern fire zone 279). Given the limited extent and lack of confidence in wind, will hold off on extending any fire highlights for tomorrow. Overnight shift can take one more look at winds for tomorrow. At the very least, widespread elevated fire weather conditions will be in place Sunday, with afternoon RHs in the single digits across much of the area, with breezy winds 15 to 25 mph. && .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 produce 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 thunderstorm, 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 /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1119 AM MDT Sat Jul 26 2025 High clouds continue to overspread the region, also bringing smoke from fires to the south. This wave will bring a few virga showers to the far western WY this afternoon, with the best chances at KCOD/KWRL between 21Z and 00Z. Added a brief VCSH for KJAC, as confidence is high there will be some shower activity nearby, but airport impacts would be lower. Any showers statewide would produce briefly gusty winds, but cigs and vis remain well above MVFR criteria. Any showers will be dissipating or moving northeast by 00Z, with clearing skies and light winds overnight. Hazy conditions return for the day tomorrow. && .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 until 8 PM MDT this evening for WYZ277-279- 280-289. && $$ UPDATE...Wittmann DISCUSSION...Hattings AVIATION...Straub FIRE WEATHER...Hattings