Forecast Discussion
862 FXUS65 KTWC 292120 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 220 PM MST Sat Aug 29 2026 .SYNOPSIS...Expect daily thunderstorms through at least Monday with storms capable of strong to severe wind gusts and heavy rainfall. After Monday storm chances begin to decrease. High temperatures will remain above normal Sunday through much of next week. && .DISCUSSION...The upper air pattern across Arizona continues to transition into a Monsoon Type IV pattern with the upper high to our east and an upper level trof to the NW. This pattern brings an increased threat of severe storms, flash flooding, and nocturnal storms this weekend into Monday. Storms have been forming over the higher terrain early this afternoon with further development over the next 3 to 6 hours. Main threat from storms today will be strong gusty outflow winds, some which may be briefly severe, blowing dust and heavy rain. The strong outflow winds may produce areas of blowing dust across Pima and Pinal counties where a blowing dust advisory is in effect from 4 pm to 8 pm. With potential rainfall rates with some of the stronger cores being 1-2"/hr, flash flooding is a threat, especially across Pinal, Pima and Santa Cruz county where a flash flood watch is in effect. Not everyone will see heavy rain or rain at all in the flash flood watch area. Tonight, across central Sonora MX near Hermosillo, a decaying MCS may send a strong outflow north towards the area and kick off some elevated storms across the central part of the forecast, or mainly across Santa Cruz, eastern Pima and western Cochise counties. Sunday: after lingering morning convection ends, storms will be developing over the higher terrain early afternoon and work their way into the lower elevations. Another chance of localized severe storms and flash flooding. Can`t rule out storms continuing late Sunday night into early Monday morning. Monday: Likely a later start to convection with less areal coverage of storms. Tuesday and Wednesday: Low-grade monsoon days as the monsoon calendar turns to September and possible tropical influences during the month. Speaking of the tropics, NHC is monitoring an area of disturbed weather, associated with a tropical wave, well south of SW Mexico. This may become the next named eastern Pacific tropical storm with some model guidance indicating that the potential track will be further east than where current Tropical storm Karina is at, and closer to Baja by the end of next week. Confidence low this far out but something to keep an eye on. Temperature wise, today is the last day of the almost two-week long Extreme Heat Warning. Highs will thus be cooler during the next 7 days but still running, except for Monday and Tuesday, above normal for the most part. && .AVIATION...Valid through 31/00Z. SCT -SHRA/-TSRA thru 30/06z, bcmg ISOLD btwn 30/06z and 30/12z. Chance of storms returning to the area aft 30/20z. Outflow SFC winds nr TSRA 35-45 kts otrw SFC winds mostly less than 10 kts and terrain driven. Clouds thru much of valid pd, SCT-BKN 8k-12k ft AGL. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect scattered afternoon and evening showers and thunderstorms through Monday (30 to 70 percent daily thunderstorm chances). Storms will be capable of strong to severe wind gusts and heavy rainfall. After Monday storm chances and coverage decrease with activity mainly from Tucson south and eastward. Temperatures will remain above normal today with a cooling trend this weekend into early next week. Minimum relative humidity values mainly 15 to 30 percent in the valleys and 20 to 40 percent in the mountains today. Minimum RH values increase to 20 to 50 percent starting Sunday into next week. 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 this evening for AZZ501>509. Flood Watch through late Sunday night for AZZ502>507-513>515. Blowing Dust Advisory until 8 PM MST this evening for AZZ501- 502-504-505. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson
NWS TWC Office Area Forecast Discussion