Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
333 FXUS65 KTWC 200834 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 134 AM MST Thu Aug 20 2026 .SYNOPSIS...Isolated to scattered afternoon and early evening showers and thunderstorms will persist across Southeast Arizona into the weekend. The primary concern with storms will be gusty outflow winds, with a secondary concern for heavy rainfall generally to the southwest and west of Tucson where deeper atmospheric moisture will reside. Otherwise, afternoon high temperatures will remain 5 to 8 degrees above normal through the weekend, with moderate to major HeatRisk. && .DISCUSSION...The upper pattern this morning is defined by large amplitude ridge of high pressure over the Southwest with the high centered over northern Arizona. The latest GOES precipitable water imagery indicated PWATs in the eastern half of our CWA between 1.00 and 1.25 inches, with deeper moisture to the west between 1.25 and 1.75 inches. Drier air between 0.65 and 0.90 inches in Chihuahua Mexico is begining to nudge into the extreme SE corner of the state with the mid-level ELY/SELY flow. We will continue to see that deep plume of moisture that was available for storms Wednesday wane and track north and a drier easterly flow sets up. The upper high center today will re- orient itself by elongating into central New Mexico. This will focus an area of deformation/lift aloft across east-central and northwest Arizona today instead of across our neck of the woods. So, given the lower moisture and the lack of larger scale lift, we will have to rely on the instability generated by strong insolation for storm development resulting in generally weaker pulse-type storms. The moisture across Southeast Arizona returns to near normal for this time of year Friday into the weekend. As the upper ridge becomes more neutrally oriented along the Rockies from NRN New Mexico into central Colorado, we will see weak divergence in the upper flow to the south and west of Tucson. Therefore, I would expect a more typical primary concern for strong gusty outflow winds across the majority of Southeast Arizona, with a secondary concern for heavy rainfall SW/W of Tucson in the deeper moisture. The Monsoon season rolls-on. && .AVIATION... Valid through 21/00Z. SCT-BKN 12-15k ft AGL through 20/20Z, then SCT-BKN 7-11k ft AGL BKN-OVC 12-15k ft AGL with isolated to scattered -SHRA/-TSRA through 21/03Z. Gusty and erratic outflow winds possible near TSRA with gusts to 40 kts. Winds outside of thunderstorms mainly light and terrain driven, with a WLY/NWLY component during the afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated to scattered afternoon and early evening showers and thunderstorms will persist across Southeast Arizona into the weekend. The primary concern with storms will be gusty outflow winds, with a secondary concern for heavy rainfall generally to the southwest and west of Tucson where deeper atmospheric moisture will reside. Otherwise, afternoon high temperatures will remain 5 to 8 degrees above normal through the weekend with moderate to major HeatRisk. An Extreme Heat Warning is in effect today and Friday for portions of the Southeast Arizona. Winds mainly light and terrain driven. Strong, gusty and erratic winds will accompany thunderstorms. Minimum relative humidities 15-25 percent in lower elevations with 25-35 percent in the higher terrain. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Friday for AZZ501-502- 504>506-509. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson