Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
068 FXUS65 KTWC 312004 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 104 PM MST Thu Jul 31 2025 .SYNOPSIS...Scattered thunderstorms are expected this afternoon and evening across much of southeastern Arizona. Periods of heavy rain, isolated strong wind gusts, and blowing dust will be hazards with any thunderstorm today. An isolated flash flood threat accompanies today`s thunderstorm activity. Thunderstorm chances begin to decrease Friday as dry air moves in through the weekend. Extreme heat is expected Friday through the weekend as high temperatures become 7 to near 10 degrees above normal. Temperatures remain above normal through next week. && .KEY MESSAGES... -Scattered thunderstorms are expected this afternoon and evening across much of southeastern Arizona. Chances begin to decrease Friday as dry air moves in through the weekend. -Periods of heavy rain, isolated strong wind gusts, and blowing dust will be hazards with any thunderstorm today. An isolated flash flood threat accompanies today`s thunderstorm activity. -Extreme heat is expected Friday through the weekend as high temperatures become 7 to near 10 degrees above normal. Temperatures remain above normal through next week. && .DISCUSSION...There are currently isolated thunderstorms in areas south and east of Tucson in the mountains. There have been a few lightning strikes so far, with some gusty winds in the 20-30 mph so far. The storms have been struggling to get tall updrafts thanks the the very dry layer aloft shown very well in the 18Z sounding. Overall, the main threats continue to be strong gusty outflow winds, possible blowing dust, and locally heavy rainfall. The threat for isolated areas of flash flooding continues as the storm motion is light at 5-10 kts, making the storms nearly stationary and rain on the same area in a short period of time. The push of moisture from the Gulf of California and Sonora, Mexico continues with current surface dew points in Western Pima County is in the low to mid 60s and satellite estimated PWs in the 1.3 to 1.4 inch range. This moisture may be able to work its way eastward through the NE flow aloft and/or outflows from thunderstorms this afternoon. The 18Z sounding showed 1.27 inches of PW, which is a tad more than yesterday, so storm activity in Tucson is certainly possible this afternoon and evening. In terms of wind, the HREF model is showing wind gusts of 30-40 mph with thunderstorms, however that may be a tad underdone as the RAP model is showing 1400-2000 J/kg of DCAPE allowing for dropping thunderstorm cores to evaporate, cool, then accelerate the overall collapse. This is shown by the 18Z sounding where there is roughly 1800 J/kg of DCAPE in Tucson. After today, a drying and warming trend begins Friday into the weekend, thanks to the high pressure system will build to our west. Temperatures will be 7 to 10 degrees above normal during this time, with an Extreme Heat Warning in effect those days. Major HeatRisk is expected for much of the valley locations, so much of the population and those without adequate hydration and air conditioning should prepare. Be sure to know where cooling centers are, move outdoor plans to the morning or evening, and keeping hydrated Friday into the weekend. Forecast models are still in disagreement with how much moisture can make it into the area early next week as the high pressure shifts back to the east. This will determine how hot the area will get mid to late next week. Some heat headlines may be needed during this timeframe, so stay tuned. && .AVIATION...Valid through 02/00Z. Isolated to scattered thunderstorms thru 01/05Z. Brief periods of heavy rainfall and gusty erratic winds possible with any thunderstorm. Winds generally below 12 kts away from thunderstorm activity, with occasional afternoon gusts to 20 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Minimum relative humidities mainly above 20 percent today across southeastern Arizona. Scattered thunderstorms are expected this afternoon and evening. Overall winds are expected to remain under 15 mph with occasional afternoon gustiness, however strong erratic winds are possible with any thunderstorm. A drying trend is expected through the weekend with high temperatures bumping up. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning from 10 AM Friday to 8 PM MST Sunday for AZZ501>507-509-515. && $$ Tetrault Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson