Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
458 FXUS65 KTWC 212037 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 137 PM MST Fri Aug 21 2026 .SYNOPSIS... Isolated to scattered afternoon and early evening thunderstorms expected through Saturday, with daily but reduced chances Sunday into next week. Strong, gusty winds and locally heavy rainfall will be possible with any thunderstorm. High temperatures will remain above normal through the coming week. && .DISCUSSION... A north-south elongated upper level high sits over the Four Corners and desert southwest today. The orientation of this high has marginally dried out the atmosphere, as the moisture source region is more northeasterly than southeasterly. Even so, adequate moisture remains today for a round of scattered thunderstorms across areas of southeastern Arizona. Precipitable water values aren`t eye popping (below an inch in Graham- Greenlee- Cochise counties and 1-1.25 inch further west) and inverted-V soundings point to a mainly wind threat, however an isolated flash flooding threat can`t be ruled out. Otherwise, gusty winds of 40-50 mph will be possible with any stronger thunderstorm, with a very isolated shot at a severe and damaging wind gust. A similar setup is forecast Saturday afternoon and early evening where isolated to scattered thunderstorms should form again. The upper level ridge will nudge east by the late weekend, which will take temperatures down a few degrees on Sunday. The current Extreme Heat Warning goes through Saturday which still looks valid, then temperatures will "cool" by 2-5 degrees Sunday and Monday. Guidance is fairly consistent in bringing the upper level ridge back over the desert southwest by the middle of next week however, and another heat headline may be needed from at least Tuesday onwards. Thunderstorm chances are about 15-30 percent on Saturday, then a bit lower Sunday into next week. Chances will depend on day to day mechanisms and the position of the upper high, but any day can still carry the threat of severe wind and flash flooding as adequate moisture remains in place. && .AVIATION...Valid through 23/00Z. Scattered -TSRA mainly through KE77-KTUS-KOLS with isolated -TSRA near KSAD-KDUG, diminishing by 22/03Z. Gusts of 35-45 kts possible with any storm. Otherwise surface winds light and terrain driven. Additional thunderstorm development expected again Saturday afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Isolated to scattered thunderstorms expected Saturday afternoon with daily but reduced chances going into next week. Temperatures will remain above normal through the coming week. Minimum relative humidity values mainly 15-30 percent each day with light and terrain driven wind. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Saturday for AZZ501-502- 504>506-509. && $$ DISCUSSION...Edwards AVIATION...Edwards FIRE WEATHER...Edwards Visit us on Facebook, X, YouTube, and at weather.gov/Tucson