Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
326 FXUS65 KTWC 202052 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 152 PM MST Wed Aug 20 2025 .SYNOPSIS...Isolated to scattered thunderstorms this week across Southeast Arizona, with day to day variability in intensity and chances. The big story for Southeast Arizona will be the extreme heat returning the second half of the week. An Extreme Heat Warning is in effect this morning through Friday evening. && .DISCUSSION...Mostly cloudy skies this afternoon with a field of cumulus clouds forming across the whole area. Isolated storms and showers have begun forming areas south and east of Tucson and will expand to be Sells eastward as the afternoon progresses. This is where there is substantial moisture and instability. The 18Z upper air sounding launched at TUS shows there is 1.52 inches of PWAT and ~1200 J/kg of DCAPE and ~1000 J/kg of MU CAPE. Storms will be moving generally to the west- southwest at a quicker speed indicating the main concern with storms today will be gusty outflow winds with a secondary concern for brief, locally moderate to heavy rainfall. Another, but equally if not more important, weather concern for the day is extreme heat. An Extreme Heat Warning is in effect for much of the lower elevations in southern Arizona now through Friday evening. Temperatures today will be around 103 to 109 degrees with Major Heat Risk increasing tomorrow to localized Extreme Heat Risk. Remember to stay hydrated and spend time indoors with A/C. If you need to spend time outside, wear light weight, light colored clothing and take frequent breaks. Take time to learn the signs of heat exhaustion and heat stroke, keeping in mind that heat stroke is an emergency. High pressure will keep temperatures above normal for the rest of the week, including both overnight lows and daytime highs. Very little reprieve for next three days. There is a wrinkle to the heat: any storm that produces a shower or a gust of wind will will tamp down the heat briefly or longer. It all depends when the storm rolls through and what remains in the heating hours of the day. Be prepared for temperatures to bounce back up when sun pokes through the clouds after a rain shower or thick low cloud layer. By the weekend, the Four Corners High will shift and morph into a ridge up through the Great Basin. This will reduce chances for precipitation, but there will be residual moisture to provide chances through the weekend. Temperatures will come down to near normal by start of the new week. Troughing will start to develop out west to shift flow into a favorable position early next week. A southeasterly to southerly flow will be taping into tropical moisture (or deep monsoon moisture), providing widespread chances for wetting rain for the middle to second half of the week. Something to look forward to after this not-so-great monsoon. && .AVIATION...Valid through 22/00Z. FEW to SCT clouds AOA 7k to 10k ft AGL across much of southeastern Arizona. Isolated storms have begun developing near KOLS and KDUG and will expand to become isolated to scattered from KAVQ southward until 21/02Z. AOA 21/01Z storms and showers will develop near KSAD moving to the southwest towards KAVQ dissipating by 21/07Z. Winds with storms will be gusty and erratic with gusts up to 40 kts possible with any thunderstorm today. Otherwise, SFC winds will be from the southeast at 5 to 10 kts becoming light and variable overnight. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect daily chances for thunderstorms and wetting rain showers into next week. Min RHs will generally be 15-20 percent in the lower elevations and 20-30 in the mountains. Winds will generally be less than 15 mph with typical afternoon gusts up to 20 mph into next week. Temperatures will be above normal this week, with an Extreme Heat Warning in the lower elevations of Southeast Arizona today through Friday. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Friday for AZZ501>507-509. && $$ Malarkey/ Strongman Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson