Forecast Discussion
932 FXUS65 KTWC 242004 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 104 PM MST Mon Aug 24 2026 .SYNOPSIS...A low grade monsoon pattern for most of this week with only limited (15 percent or less) storm chances each day for most locales. Storm chances return to more typical levels by this weekend. High temperatures will remain well above normal through the week with an Extreme Heat Warning in effect for much of southeast Arizona. && .DISCUSSION...We can`t rule out a few daily afternoon showers and storms, but we are in a low grade monsoon pattern with the bigger story shifting back to extreme heat as the mid/upper level high strengthens and nudges into southeast Arizona. High pressure aloft is not as conducive to rising motion within the atmosphere which is needed for storms. This afternoon we still have clouds out over central portions of Pima County which will likely inhibit solar insolation from reaching its full potential. Meanwhile, we still do have adequate moisture around with surface dewpoints in the upper 50s to low 60s from the Tucson Metro south and westward. With modest moisture and instability (~1000 J/kg), there is a small chance (10-15%) for a few showers and storms mainly south of Tucson focused mainly over the high terrain later this afternoon. Tomorrow looks similar to today with the upper high stretching, becoming elongated from southwest to northeast and dragging the center of the mid level high toward southwest NM/southeast AZ. The best chance (10-15%) for a few showers and storms remains along the outer periphery of the high or focused mainly along the international border from Nogales west. Wednesday into Thursday, the mid/upper high will pretty much be stacked overhead which will act to suppress shower and storm activity, but there could be (10-30%) a few storms again on the outer periphery of the high pressure where there is less subsidence. Friday into Saturday the high shifts east toward New Mexico. Whenever a mid/upper high shifts we tend to see stretching of the upper levels in the atmosphere helping air be more conducive to rising motion. Thus, chances for showers and storms increase again areawide on Friday (10-30%) into the weekend (30-50%). That being said, this is all primarily dependent on the actual evolution of the mid/upper level high pressure. For now, we have an Extreme Heat Warning in place through 8 PM Saturday with high temperatures expected to peak midweek 6 to 10 degrees above normal. && .AVIATION...Valid through 26/00Z. VFR at all TAF locales with -SHRA/-TSRA between Three Points and Ajo. This activity is moving north. Expecting aftn/early evening Isolated shower/storm activity near and south of KOLS with dry conditions elsewhere. Cloud decks FEW to perhaps SCT between 10-13k ft AGL. SFC winds this afternoon and early evening from the W/NW around 4-9kts with gusts up to 16 kts. Terrain driven overnight. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated thunderstorms (15 percent or less chance) for most locales through Thursday, though slightly higher chances along the immediate Int`l border and White Mountain region. Thereafter, storm chances increase by Friday afternoon and evening to more typical levels around 20 to 50 percent. Temperatures will remain well above normal through most of the week with a cooling trend by the end of the forecast period on Sunday. Drier conditions return Tuesday with minimum relative humidity values mainly 10-18 percent in the valleys and 20-30 percent in the mountains. Minimum RH values increase to 20-30 percent this weekend in valleys and 30- 50 percent in the mountains. Winds will generally remain less than 15 mph and terrain driven through the week. && .TWC WATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning until 8 PM MST Saturday for AZZ501-502- 504>506-509. Extreme Heat Warning from 10 AM Tuesday to 8 PM MST Saturday for AZZ503-507-508. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson
NWS OUN Office Area Forecast Discussion