FXUS65 KTWC 222028 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 128 PM MST Sat Aug 22 2026 .SYNOPSIS... Isolated to scattered afternoon and early evening thunderstorms expected this weekend, with daily but gradually reduced chances through 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... Water vapor imagery shows a ridge of high pressure over the intermountain west. The ridge axis is just to our east. PWATS are 1.25 inches by Ajo with lower values down to 0.80 inches in Douglas. Plus, the upper level flow is southerly to slightly southeasterly. This sets up the favorite area for any thunderstorms west and south of Tucson today because of the better PWATS values and lots of sunshine to get higher CAPE values. 12Z HREF has 50-70% chances for thunderstorm wind gusts greater than 35 mph over central Pima County (between Three Points and Ajo). This will bring a risk for blowing dust, depending on how dry the soils tops have been in the last 24 hours. Any storm has the ability to produce brief locally heavy rainfall, posing a 5% risk for flash flooding. Thunderstorm activity will wane down after sunset. Going forward, high pressure will stay around the region for the long haul, prolonging our heat. The ridge axis will slowly move west over the region by Tuesday which will elevate temperatures and crank up the HeatRisk across the region to widespread Major and Extreme. Cochise and Santa Cruz Counties risk will increase to Major by Tuesday and Wednesday. Extreme Heat Warning has been extended for most of Pima, Pinal, and the valleys of Graham and Greenlee through the rest of the new week. Some areas of the warned area will see a brief moment of "cooling" (by a 1-3 degrees) on Sunday and Monday while other areas, such as built up population areas, will continue to experience Major HeatRisk; especially with the compounding heat over the last days and above normal overnight lows. Any thunderstorms and increase thick clouds can reduce or delay those hot temperatures. Daily slight chances for thunderstorms will continue through Monday, mainly favoring west and south of Tucson. Chances will reduce each day as the ridge axis moves over the region. Tuesday through Thursday will be more of the down days during period. Long range models indicate an increase trend of thunderstorms by the end of the week due to the favorable upper level flow and pattern. In the extended, CPC outlooks for the 8-14 days has a 60-80% likely above normal temperatures and near normal precipitation for Southeast Arizona. && .AVIATION...valid through 24/00Z. FEW-SCT clouds 9-13k ft AGL through forecast period with locally BKN between 22/21Z and 23/10Z. Expect isolated to scattered SHRA/TSRA this afternoon, mainly west of a KFHU-KSAD line, diminishing by 23/06Z. SHRA/TSRA chances return after 23/21Z mainly south and west of KTUS. Gusts in excess of 40 kts are expected with the stronger storms. Otherwise surface winds light and terrain driven. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Isolated to scattered thunderstorms expected this weekend with daily but gradually reduced chances as next week progresses. Temperatures will remain above normal through the coming week. Dryer conditions will return in the middle of the week with minimum relative humidity values mainly 10-18 percent in the valleys and 20-30 percent. Winds will generally remain less than 15 mph and terrain driven through the week. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Saturday for AZZ501-502- 504>506-509. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson