Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
545 FXUS65 KTWC 150835 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 135 AM MST Sat Aug 15 2026 .SYNOPSIS...Expect a slight chance of afternoon thunderstorms today as the combination of drier-air and a more stable atmosphere aloft will limit thunderstorm activity across all of Southeast Arizona. Hot conditions will return late this weekend with an Extreme Heat Watch in effect for portions of Southeast Arizona Monday though Wednesday of next week. A more active thunderstorm pattern returns the second half of next week. && .DISCUSSION...The upper pattern this morning is defined by a strong ridge of high pressure centered over Louisiana and a broadening trough of low pressure along the West Coast. The latest GOES precipitable water imagery indicated a much drier airmass has positioned itself into Southeast Arizona, with PWATs around an inch across Cochise county and around 1.25 inches across the Tucson Metro and the lower deserts of Pima and Pinal counties. Lower-level moisture still hanging-on a bit more than expected primarily due to the recently saturated soils, with surface dewpoints generally in the low to mid 60s. The exception to the rule is across Graham and Greenlee counties with dewpoints in the lower 50s. Although the will be a lack of larger scale lift across the area, there may be enough moisture for a slight chance of afternoon showers and thunderstorms. There wont be much threat for widespread heavy rain today, but with the drier mid-levels across the area, some of the storms to do develop will be capable of producing localized gusty and erratic winds to 40 mph. The upper pattern over the next few days will become more stable as the 500mb upper-high center slowly moves overhead by Sunday and the 300mb high develops over the northern Baja. Weak inverted trough near extreme NE Mexico will rotate toward our neck of the woods this weekend, impacting the far SE portions of AZ Sunday afternoon into Monday afternoon. Not too much moisture around to work with, but we may see more thunderstorms activity starting Sunday across Cochise county and along the International Border. The more impactful weather element in this forecast package will involve the heat next week. With high pressure aloft, we will see thicknesses increase enough to put portions of Southeast Arizona in the major HeatRisk category with isolated pockets of extreme. An Extreme Heat Watch in currently in effect from late Monday morning through Wednesday evening. Although models are still bullish with keeping the high center nearby, models move the high center slightly north which will open Southeast Arizona up to a more favorable easterly flow for thunderstorm activity. Not only will this pattern result in a tad more lower-level moisture to advect into the area from the east but the possibility of more cloud cover may moderate surface heating by a degree or two the second half of next week. For this reason, we have decided to hold off on extending the Extreme Heat Watch into next Thursday and Friday. && .AVIATION... Valid through 16/12Z. FEW-SCT clouds 12-15k ft AGL BKN around 20k ft AGL through 15/20Z becoming SCT-BKN 8-12k ft AGL BKN around 12-15k ft AGL. A slight chance of -SHRA/-TSRA centered mostly over higher terrain through around 16/02Z. Gusty and erratic winds possible near TSRA with gusts approaching 35 kts. Otherwise, SFC winds light and terrain driven through midday, then NWLY at 7-12 kts with ocnl gusts to around 20 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A slight chance of storms this weekend focused mainly south and east of Tucson and over the higher terrain. A more active monsoon pattern looks to return around the middle of next week. Minimum relative humidity will be 20-35 percent today lowering to around 15-30 percent thereafter. Temperatures will warm-up to above normal by Sunday and persist well into next week. Outside of thunderstorms, winds will be terrain driven around 10 mph with occasional afternoon gusts to 20 mph. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Watch from Monday morning through Wednesday evening for AZZ501-502-504>506-509. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson