Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
645 FXUS65 KTWC 161644 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 944 AM MST Sun Aug 16 2026 .UPDATE... No change in thinking with this update from the previous discussion. 12Z high-resolution modeling shows just very isolated thunderstorm activity this afternoon - early evening, mainly tied to eastern terrain including the White Mountains and Chiricahuas. Can`t rule out isolated build-ups over terrain into southwest Cochise and Santa Cruz as well. && .SYNOPSIS... The combination of drier-air and a more stable atmosphere aloft will limit thunderstorm activity across Southeast Arizona to areas mainly along and near the Arizona and New Mexico state line, especially along over the higher terrain. Hot conditions will return this week with an Extreme Heat Warning in effect for portions of Southeast Arizona Monday though Friday. Otherwise, a more active thunderstorm pattern will return the second half of the upcoming week. && .DISCUSSION... The upper pattern this morning is defined by a ridge of high pressure centered over far ERN Texas, a distinct inverted trough centered near the Big Bend of SW Texas and a developing high center developing over Sonora Mexico. The inverted trough looks impressive on WV imagery this morning with a movement taking it toward SRN New Mexico today. As this shift happens, it will promote the upper-high over Sonora Mexico to strengthen with a weak col in the upper-flow developing along the Arizona/New Mexico border. The latest GOES precipitable water imagery indicated a dry-ish airmass across Southeast Arizona, with PWATs 0.90-1.10 inches across Cochise/Graham and Greenlee, 1.10-1.30 inches across SE Pinal/ERN Pima and Santa Cruz and 1.30-1.75 inches across central and western Pima. The best larger scale lift will occur along the AZ/NM border today near this upper-level col. Even though the airmass is currently dry, there is a pocket of higher PWATs 1.25-1.50 inches over northern Chihuahua Mexico and south-central New Mexico that will advect into far SE AZ late late this afternoon and into the evening. With this, I would expect more isolated coverage of showers and thunderstorms, especially over the higher terrain along the AZ/NM border. With the drier mid- levels, I would expect these storms to only be able to produce brief moderate-heavy rain but more capable of producing gusty outflows to 40-45 mph. In fact, the 16/00Z HREF shows a 30-50 percent neighborhood probability of storm outflows 35+ kts in the aforementioned area. Otherwise, The inverted trough stalls out across the bootheel of NM Monday but does force the upper-high center in Sonora Mexico to lift NW into the northern Baja. As this happens, a more favorable area of deformation aloft develops across the eastern half of the forecast area. The airmass is still rather dry-ish on Monday, but it should be enough to increase the coverage of storms from isolated to widely scattered while expanding west into ERN Pima and Santa Cruz. Heavy rainfall still is not a major threat with these storms, but the impact of gusty winds increases Monday. This is supported by the 16/00Z HREF neighborhood probability of storm outflows of 35+ to 50-70 percent from Tucson northeast into Graham county. The big weather story this week will be the return of the heat with major HeatRisk returning to the majority of Southeast Arizona. A Extreme Heat Warning is in effect Monday through Friday of the upcoming week for portions of Southeast Arizona. The upper-high center will strengthen as it slowly drifts north during the week, eventually making its way to near Las Vegas by 21/00Z Thursday afternoon. This position will open Southeast Arizona up to a more favorable easterly flow for thunderstorm activity late this week into next weekend. The Monsoon season rolls-on despite the heat. && .AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/... Valid through 17/12Z. FEW-SCT 12-15k through 16/20Z this afternoon, then FEW-SCT 8-12k ft AGL SCT-BKN 12-15k ft AGL into the early evening. Isolated -SHRA/-TSRA mainly over the higher terrain along the Arizona and New Mexico state line between 16/22Z and 17/02Z. Gusty and erratic winds possible near TSRA with gusts to 35-40 kts. Otherwise SFC winds light and terrain driven through 16/20Z, then west to northwest 7-12 kts with occasional gusts to 20 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... The combination of drier-air and a more stable atmosphere aloft will limit thunderstorm activity across Southeast Arizona to areas mainly along and near the Arizona and New Mexico state line, especially over the higher terrain. Hot conditions will return this week with an Extreme Heat Warning in effect for portions of Southeast Arizona Monday though Friday. A more active monsoon pattern looks to return around the middle of the upcoming week. Minimum relative humidity will generally be 15-30 percent. Outside of thunderstorms, winds will be terrain driven around 10 mph with occasional afternoon gusts to 20 mph. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning from 10 AM Monday to 8 PM MST Friday for AZZ501-502-504>506-509. && $$ UPDATE...Edwards Visit us on Facebook, X, YouTube, and at weather.gov/Tucson