Flash Flood Warning 181, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
1208 PM MST Thu Sep 3 2026

.SYNOPSIS...
Expect scattered to numerous thunderstorms each
afternoon and evening through the weekend as tropical moisture
moves in. The main threat will be heavy rainfall leading to
areas of flash flooding. High temperature will will fluctuate
between normal and a few degrees below normal.

&&

.DISCUSSION...
Southwest flow has set up across the region, pulling in tropical
moisture from Hurricane Marie. PWATS over Southeast Arizona are
at the 90th percentile or higher for this early September. The
above normal moisture will prime the day for heavy rainfall
risk. The latest CAM model have confidence for this afternoon
storms to produce up to 1-1.5 inches with pockets up to 2 inches
in a short amount of time. Ground conditions are primed and can
react quickly to heavy rainfall because of the previous 48 hour
rainfall. Areas south of Tucson will be the most susceptible to
quicker response in washes and creeks and heighten risk for
flash flooding. As result, there is a Flash Flood Watch for the
eastern Pima (including Tucson metro), Santa Cruz County, and
eastern Cochise County (Benson south to Sierra Vista/Hereford)
for today and through the early tomorrow morning. Several models
continue to show activity lasting through the nighttime and
adding more rainfall accumulation.

Tomorrow, moisture will shift more east of Tucson, allowing
Cochise, Graham, and Greenlee Counties to have better chances
for rain showers and thunderstorms. Rainfall amounts can be an
inch with localized higher amounts. WPC has a slight risk (<15%)
for flash flooding those counties. Thunderstorm activity will
drop around sunset.

Looking into the holiday weekend. The upper pattern will
generally stay the same with a closed low over the Pacific
Northwest and ridging to the east. Yet, the best chances for
rain showers and thunderstorms will mainly be confined to the
International Border and east of Tucson through the weekend.
Better widespread chances will return by next week with a
reemergence of deeper moisture.

Temperatures will be hovering near normal to slightly below
normal through the forecast period.

The 8-14 day CPC outlook has a 50-60% likely above normal
precipitation and 33-50% leaning above normal temperatures.

&&

.AVIATION...valid through 05/00Z.
SCT-BKN clouds 7-12k ft AGL through much of the forecast
period. Scattered TSRA/SHRA this afternoon and lasting through
the overnight period. Although the overnight TSRA/SHRA activity
will be more isolated. Near any thunderstorm will have strong
gusty winds, heavy rainfall, and brief lowering of ceilings.
Outside of thunderstorm winds, winds will be west to
southwesterly 5-10 kts and again after 04/18z. Light and terrain
driven at other times. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...
Expect daily scattered thunderstorms each
afternoon and evening today into early next week. There will be
some variation in coverage day to day, but expect the bulk of
the activity from central Pima County eastward. Heavy rainfall
leading to flash flooding will be the main threat. Temperatures
will be around normal to a few degrees below normal into early
next 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...
Flood Watch through late tonight for AZZ503-504-507-513-514.

&&

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