Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
790 FXUS65 KTWC 242020 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 120 PM MST Fri Jul 24 2026 .SYNOPSIS... Isolated thunderstorms through this evening will bring a slight chance of a severe wind gust threat. High temperatures will be 8 to 12 degrees above normal through Saturday, with an Extreme Heat Warning in effect through early Saturday evening. Increasing coverage of thunderstorms is expected Saturday going forward into next week. && .DISCUSSION... The upper level ridge sits just to the east centered over southern New Mexico today, a location that has a limiting influence on thunderstorm coverage for southeastern Arizona. While the synoptic setup isn`t ideal for monsoon activity, there remains adequate lower level moisture characterized by 55-60 degree surface dew points and intense surface heating, increasing MLCAPE values to 500-1000 J/kg. To add another ingredient to the mix, wind speeds in the mid-levels are notable for this setup and will produce around 20-25 kts of effective shear. The combination of these factors will provide a severe wind threat with any thunderstorm that sustains itself today, though the coverage is again less certain and likely more isolated given the nearby ridge. 12Z ensemble guidance highlights the somewhat more likely risk of a severe wind gust in areas south and west of Tucson, mainly from a Tucson-Nogales line west to Sells. But any location will have a small but non- zero risk. The upper ridge will lift north slightly and become more centered over the Four Corners on Saturday, putting southeastern Arizona in a more favorable location for more widespread thunderstorm activity. Moisture will be on the rise with precipitable water values increasing to 1.2-1.6 inches and mid- level flow will remain around 15-20 kts, providing an instability/shear parameter space for a severe wind gust threat. Thunderstorms should initially form over the Sky Islands and White Mountains during the first half of the afternoon, increasing in coverage and moving into the lower desert locations in the late afternoon and the evening from central Pima eastward. Westward expansion will depend on outflow collisions but adequate low level moisture and mid-level support exist that convection should move into western Pima in the late evening, though likely with less severity with the loss of daytime heating. Blowing dust and flooding will also be threats with any thunderstorm, though the flash flooding threat will be on the lower side as storm movement should preclude widespread problematic rainfall totals. Above normal high temperatures remain a hazard today and Saturday with highs 8 to 12 degrees above normal. Additionally, morning lows will be quite warm, especially from Tucson west where Saturday morning lows will remain above 82 degrees. An Extreme Heat Warning remains in effect until Saturday evening. The upper level high remains in a similar location Sunday through at least the first half of next week, providing daily chances for thunderstorm activity. Temperatures by Monday should fall back to around normal, though an increase is possible by the end of the work week as the upper high center moves more over Arizona. && .AVIATION...Valid through 25/00Z. FEW-SCT clouds with 8k-12k ft ceilings this afternoon and evening with isolated TSRA, especially north of KSAD and near, south, and west of KTUS-KOLS. Any thunderstorm may produce strong and erratic wind gusts, with a slight chance of a severe wind gust. Otherwise surface winds northwest 5-10 kts, becoming light and terrain driven after 25/03Z. Thunderstorm chances return and become more widespread across southeastern Arizona Saturday afternoon and evening. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Strong high pressure aloft will bring high temperatures up to 8 to 12 degrees above normal through Saturday. Isolated thunderstorm activity will linger this evening, then more widespread chances are expected Saturday afternoon and evening. Thunderstorms should form over the Sky Islands and White Mountains in the first half of the afternoon, spreading into desert locations westward through central Pima county in the late afternoon and early evening, moving into western Pima in the late evening. Any thunderstorm will bring a threat of severe, erratic wind gusts as well as brief heavy rainfall and an isolated threat of flash flooding. Deeper moisture will move into the region this weekend and continue daily thunderstorm chances into much of next week. Minimum relative humidity values will increase from 15-20 percent in desert location and 30-40 percent in the mountains on Saturday to above 20-40 percent Sunday through mid-week next week. Winds this weekend will mainly be light and under 12 mph outside of thunderstorms. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Saturday for AZZ501>509. && $$ DISCUSSION...Edwards AVIATION...Edwards FIRE WEATHER...Edwards Visit us on Facebook, X, YouTube, and at weather.gov/Tucson