Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
225 FXUS65 KTWC 232042 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 142 PM MST Thu Jul 23 2026 .SYNOPSIS... Just isolated thunderstorm activity tonight and Friday as the combination of drier air and a ridge of high pressure aloft move into the region from the east. High temperatures will increase to 5 to 10 degrees above normal with the arrival of this high pressure ridge. An Extreme Heat Warning is in effect Friday and Saturday. The upper level pattern will then become more favorable for thunderstorm activity Saturday into next week. && .DISCUSSION... In the upper levels, a ridge is centered over Texas and the southern plains today while Tropical Storm Bertha begins to cross the Texas Gulf Coast and Hurricane Fausto approaches Hawaii in the Pacific. Though mean southeasterly flow continues into southern Arizona via the ridge to the east, the placement of this ridge has warmed temperatures aloft, suppressing thunderstorm chances today to just isolated coverage (10-15 percent) across southeastern Arizona. Satellite derived precipitable water values this afternoon range from around 1 inch in the far southeast to over 1.5 inches in southwest Arizona, adequate for at least a few thunderstorms to form with brief heavy rainfall and a 30-40 mph wind gust threat. As the ridge center nudges west on Friday so will the thunderstorm chances with just slight chances (10-20 percent) expanding west into central- western Pima. The discussed westward shift of the upper ridge will also bring a heating trend to southeastern Arizona. High temperatures will become 5-10 degrees above normal Friday and Saturday, ranging from 105-112 in the Tucson Metro, Western Deserts, and Upper Gila River Valley. In lower elevation areas of Santa Cruz and Cochise counties highs range from 100-105. Can`t rule out highs coming in a bit hotter than currently forecast with the strength of the ridge moving overhead. NBM probabilities give a 33% chance for the Tucson airport to hit 110 degrees on Saturday. Additionally notable will be the overnight lows with forecast lows from Tucson west ranging from 82 to 88 degrees Saturday morning. The lack of relief from the heat plus the afternoon highs combine to produce Major HeatRisk with the Extreme Heat Warning in effect Friday and Saturday. The ridge center is expected to lift north after shifting west and become centered closer to the Four Corners region on Saturday, putting southeastern Arizona under a more favorable pattern for thunderstorm activity. After a period of modest drying through Friday, moisture return should arrive in earnest through Saturday, partially driven by potential northerly driven outflows from northern Mexico thunderstorm activity and the crossing remnants of Tropical Storm Bertha. The combination of this incoming moisture with Saturday`s hot temperatures and some modest mid-level flow will provide an environment for strong to severe thunderstorms capable of severe wind gusts, blowing dust, and heavy rainfall rates. In collaboration with SPC, a Day 3 Marginal Risk for severe thunderstorms has been introduced on Saturday for much of southeastern Arizona. The upper ridge will remain in a similar spot for the coming days into next week, bringing daily chances for thunderstorms across the region with day to day variability. This will also bring temperatures down closer to normal by Monday. Looking down the line, ensembles bring the upper ridge center into Arizona and amplify the ridge by the end of next week, which would increase temperatures and reduce thunderstorm chances, depending on where this ridge center sets up. && .AVIATION...Valid through 24/00Z. Isolated thunderstorms through 24/03Z with FEW-SCT ceilings 8k-11k ft. Surface winds light and under 10 kts though any thunderstorm may produce a wind gust up to 35 kts. Light and terrain driven winds through Friday with additional slight chances for thunderstorms Friday afternoon and evening. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... A ridge of high pressure building aloft will raise temperatures through Saturday with high temperatures becoming 5 to 10 degrees above normal Friday and Saturday. This trend will also reduce thunderstorm chances on Friday to just isolated coverage in the afternoon and evening. Minimum relative humidity values Friday and Saturday fall to 15-20 percent in desert locations while winds overall will be light and under 12 mph. Deeper moisture is expected to return through the weekend with increasing thunderstorm chances late Saturday afternoon through the evening. Any thunderstorm may come with the threat of strong gusty winds and heavy rain. Daily chances for thunderstorms return in the following days into next week. Minimum relative humidity values should rise as well Sunday through the first half of next week. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning from 10 AM Friday to 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