Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
388 FXUS65 KTWC 201530 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 830 AM 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. && .UPDATE...Mostly cloudy skies this morning with morning temperatures 3 to 6 degrees warmer than yesterday. 30-50% chance for isolated to scattered showers and thunderstorms starting early this afternoon. Showers and storms will be focused Sells eastward where there is substantial moisture (PWATs around 1.2 to 1.4 inches) and instability (900-1100 J/kg of DCAPE). Storms will be moving generally to the southwest at a quicker speed indicating the main concern with storms today will be gusty outflow winds with brief, locally moderate to heavy rainfall. The secondary, but equally if not more important, weather concern for the day is extreme heat. Starting at 10 AM MST, an Extreme Heat Warning is in effect for much of the lower elevations in southern Arizona. Temperatures today will be around 103 to 109 degrees with Major HeatRisk. 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. && .PREV DISCUSSION... /issued 210 AM MST Wed Aug 20 2025/ .DISCUSSION...Four Corners High will continue to influence the region with heat and chances for thunderstorms. Today, upper level easterly winds will push the above normal moisture westward towards Sells. Models show storms initiating from Benson west toward Sells in the early afternoon. This area has the highest amount of CAPE compared to the rest of the region and better instability due to surface heating. Therefore, storms and rain showers will start to form in the early afternoon and move westward throughout the day. These storms are capable of producing strong gusty winds of 30-40 mph and brief locally heavy rainfall. By tomorrow, the upper level winds will shift slightly and shoving the moisture around the region. Thus, giving variability of storm coverage and intensity. 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. Major HeatRisk will be experienced for low valley areas, such as Safford, Tucson, and out west. Extreme Heat Warning is in effect this morning through Friday evening for those locations. 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 more. 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 21/12Z. FEW-SCT clouds AOA 10-15K ft AGL with SCT layer at 20k ft AGL this morning. By 20/18Z, SCT-BKN AOA 10-15k ft AGL with scattered -SHRA/-TSRA through 21/06Z. Light and terrain driven SFC winds this morning and again after 21/06Z. In the afternoon, easterly winds at 8-12 kts with gusts up to 20kts. 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 Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson