Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
849 FXUS65 KTWC 121702 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 1002 AM MST Sat Sep 12 2026 .SYNOPSIS...A more typical isolated to scattered coverage of storms is forecast this weekend into next week. Daily high temperatures will fluctuate between near normal and a few degrees below normal. && .UPDATE...Forecast focus today will be isolated to scattered storms possible again primarily south and west of Tucson. Given precipitable water values between 1 and 2 inches (1.3 across eastern areas, 1.5 inches in the Tucson Metro, and 1.8 inches across western Pima County) heavy rainfall will again be the primary threat with any storms that form. Secondarily, cannot rule out gusty outflow winds and/or small hail with the strongest storms. Plenty of instability in place (1500-2500 J/kg MLCAPE) helps add to my confidence of there being some level of storm activity. However, the big question is how will the coverage compare to yesterday? Can the available instability be utilized? Yesterday, the HREF and REFS members appeared to overdo the storm coverage and intensity. Today, looking like coverage will end up being isolated in nature given the lack of broad scale dynamic forcing outside of normal terrain forcing. With the lack of shear and slower storm motions my confidence in storm coverage becoming more widespread during the afternoon is lower compared to yesterday, but outflows from storms that do get going could always aid as a lifting mechanism later in the day. We`re already seeing some cumulus going up across the area, and given the impressive moisture profile for this time of year it would be no surprise if we have an earlier start to storm activity like yesterday before Noon MST. The HREF depicts a slight chance (10%) for exceeding 3 inches this afternoon pinpointing areas south and west of Tucson. Overall, my thinking is that we have the ingredients for localized flash flooding concerns again today focused mainly south and west of Tucson across Santa Cruz county and areas around the Baboquivari Mountains. && .PREV DISCUSSION... /issued 300 AM MST Sat Sep 12 2026/ Partly to mostly cloudy conditions prevailed early this morning with a few storms occurring west of Picacho Peak. This weekend will see isolated to scattered thunderstorms with the usual threats, gusty outflow winds and brief heavy rain. Monday, at this time, looks to be a bit more active possibly associated with a weak disturbance moving north across the area. QPF is trending up with WPC placing portions of the forecast area under slight risk for excessive rainfall with the potential for stronger storms producing rainfall rates of 1-2"/hr leading to the increased risk of localized flash flooding. Time will tell as its difficult to time disturbances this far out. Will keep daily threat of afternoon/evening storms Tuesday thru Friday with day-to-day changes in areal coverage. High temperatures will mostly be around normal for the next 7 days. && .AVIATION...Valid thru 13/12Z. SCT-BKN 6k-9k ft AGL. ISOLD -SHRA/TS W of KTUS til 12/15z then SCT SHRA/TSRA btwn 12/18z to 13/04z. SFC winds terrain driven and less than 10 kts til 12/17z and again aft 13/05z. At other times, WLY/NWLY at 6-10 kts Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A typical isolated to scattered coverage of storms is forecast this weekend into next week. High temperatures will will fluctuate between near normal and a few degrees below normal. Min RH values mainly 20 to 45 percent in the valleys and 35 to 65 percent in the mountains over the next week. RH recoveries will continue to be excellent overnight. Winds will generally remain less than 15 mph and terrain driven. Gusty and erratic winds will accompany thunderstorms. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && $$ DVS Visit us on Facebook, X, YouTube...and at weather.gov/Tucson