Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
014 FXUS65 KTWC 010920 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 220 AM MST Tue Sep 1 2026 .SYNOPSIS...Storm chances and coverage decrease today and Wednesday, then increase again Thursday into the weekend. High temperature will be below normal during the work week then near normal this weekend. && .DISCUSSION...The upper air pattern remains in a transitional phase this week with high pressure centered over the southeast U.S. and troughing over the west coast. After an active weekend and beginning of the week monsoon activity will decrease over the next couple of days. Southwesterly flow in the mid-levels will reduce moisture slightly today and Wednesday. Enough moisture will still be in place for isolated thunderstorms south and east of Tucson each afternoon and evening. CAMs show Wednesday as being the slightly more active day with storms capable of gusty outflow winds and brief heavy rainfall mainly along the international border. Late in the week into the weekend the tropics will begin to come into play along with a deepening trough over the Pacific Northwest. Just named tropical storm Marie, currently centered well south of Baja, will be moving northwestward over the next few days. The NHC track keeps it well west of Baja as it travels northward, but there is some uncertainty in the track after Friday. Some models favor a more northward track rather then northwestward. This will depend on how far south the aforementioned upper level low travels. However even with the uncertainty in the track ensembles are in fairly good agreement with an increase in moisture from the tropics beginning as early as Thursday. Expect monsoon thunderstorm activity to ramp back up starting Thursday into the weekend. By Friday mean PWAT values are 1.5"-1.8" from Tucson westward. PWAT values near 2" in far western Pima County are not out of the question. This increase in moisture will lead to a risk for heavy rainfall and flash flooding. WPC already has southeast Arizona under a slight risk for excessive rainfall Thursday and Friday. High temperatures will remain a few degrees below normal through the rest of the work week then warm a few degrees to around normal this weekend. && .AVIATION...Valid through 02/12Z. Mostly clear skies this morning with some mid-level clouds along the AZ/NM border. Isolated storms from KTUS south and eastward will be possible starting around 01/20Z through 02/03Z. Skies will be SCT-BKN 8k-12k ft AGL this afternoon into the evening. Gusty winds to 30 kts will be possible near TSRA. Otherwise winds will be west northwest 5-10 kts this afternoon and evening, and light and terrain driven at other times. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect isolated storms Tuesday and Wednesday with activity mainly from Tucson south and eastward. Then expect an increase in storm chances Thursday into the weekend as tropical moisture moves in. Temperatures will be around normal today through the coming work week. Minimum relative humidity values mainly 20 to 45 percent in the valleys and 30 to 60 percent in the mountains over the next week. Winds will generally remain less than 15 mph and terrain driven through the week. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Hardin Visit us on Facebook, X, YouTube, and at weather.gov/Tucson