Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
521 FXUS65 KTWC 131629 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 929 AM MST Sun Sep 13 2026 .SYNOPSIS...An active week ahead with daily chances of showers and thunderstorms. Daily high temperatures will fluctuate between near normal and a few degrees below normal. && .UPDATE...Mostly sunny skies this morning across southeast Arizona per latest visible satellite imagery. Plenty of moisture out there with PWAT values ranging from about 1.3 inches to the east of Tucson to 1.5 to 1.7 inches from Tucson westward. These values are about 150 to 200 percent of normal for this time of year. Latest SPC RAP mesoanalysis along with model soundings show there is a bit of convective inhibition to work through so convective development will be a bit delayed compared to the early start yesterday. Even as such, we should break through capping around midday or early afternoon with isolated to scattered showers and thunderstorms this afternoon. CAMs/HREF are pretty consistent today with isolated to scattered showers and thunderstorms mainly from Tucson eastward, though a storm or two is possible as far west as Sells. No obvious upper level support today to help things along though in this southerly flow, though more ill-defined disturbances can sneak up on us. Main threat will continue to be locally heavy rain with an isolated flash flood threat. See previous discussion below for additional information. && .DISCUSSION...Moist southerly flow aloft for much of the next 7 days will keep anomalously high PWAT values for September across the area. This will lead to a daily threat of isolated to widely scattered flash flooding with some of the strongest storms producing rainfall rates of 1-2"/hr, possibly higher, mainly during the afternoon and evening hours. Model guidances are hinting that Monday and Wednesday will see the greatest threat of scattered heavy rain and flash flooding due to the potential for upper level disturbances moving across the area. Thursday also looks interesting as models are bringing the remnants of a tropical upper low, which is still developing off the Mexican coast this morning well S-SE of the tip of Baja, north across NW Mexico on the western flank of the sub-tropical ridge with the high centered over Louisiana. Confidence low on timing of this feature this far out. WPC is highlighting the eastern portions of the forecast area Monday, Wednesday and Thursday for excessive rainfall. The potential wet week ahead may lead to some enhanced flows in washes, creeks, and rivers across the forecast area that are already saturated. High temperatures this week will show daily variations from near normal to several degrees below normal. && .AVIATION...Valid thru 14/12Z. SCT-BKN clouds AOA 20k ft AGL until 13/17z, then SCT-BKN 8k-10k ft AGL with ISOLD-SCT SHRA/TSRA thru 14/04Z. SFC winds terrain driven less than 10 kts thru 13/17z and then again aft 14/05z. At other times, WLY/NWLY 6-10 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...An active week ahead with daily chances of showers and thunderstorms. High temperatures 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. && $$ Visit us on Facebook, X, YouTube, and at weather.gov/Tucson