Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
046 FXUS65 KTWC 202025 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 125 PM 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 mainly west and north 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...As of late this morning cloud buildups were forming on the higher Terran areas mainly east of Tucson indicating daytime heating was picking up. However, the drier airmass nudging in from the east has been preventing towering cumulus from rapidly becoming stout as they were yesterday afternoon and evening. Lingering surface moisture combined with heating will still be sufficient enough for a few areas of pulse thunderstorms to develop this afternoon and evening, but with lack of shear they will struggle to survive. The main concerns with the strongest storms will be gusty outflow winds to around 35-45 mph, locally heavy rainfall, and small hail. Otherwise, shower and storm chances (10-30%) continue through next week with day to day variability. We continue to monitor the heat situation closely given moisture trends and daily chances for storms. The lingering moisture has helped keep afternoon high temperatures in the low 100s across the Tucson Metro, but has also kept overnight low temperatures elevated in the upper 70s and low 80s. Daytime highs and overnight lows continue to support Moderate to Major HeatRisk levels prompting the extension of the Extreme Heat Warning through Saturday evening. Sunday and Monday daytime high temperatures cool areawide by a few degrees but nighttime low temperatures may still remain elevated. Tuesday through Thursday of next week will need to be monitored closely for an additional period of above normal temperatures and the need for heat headlines, but I am not convinced we can rid of surface moisture enough to suppress storm chances altogether. && .AVIATION...Valid through 22/00Z. SCT-BKN 7-11k ft AGL BKN-OVC 12-15k ft AGL with isolated to widely scattered -SHRA/-TSRA through 21/03Z and again after 21/19Z. 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 widely scattered showers and storms will return to Southeast Arizona this afternoon. The primary concern with the strongest storms this afternoon will be gusty and erratic outflow winds, locally heavy rainfall, and small hail. Otherwise, storm chances continue through the weekend with day to day variability. Hot daytime high temperatures and elevated overnight low temperatures will persist with an Extreme Heat Warning now in effect for portions of southeast Arizona through Saturday. Outside of thunderstorms, winds will be mainly light and terrain driven. 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 Saturday for AZZ501-502-504>506-509. && $$ DVS