Flash Flood Warning 204, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
1244 PM MST Mon Sep 14 2026

.SYNOPSIS...An active week ahead with daily chances of showers and
thunderstorms. Elevated precipitation chances today with a Flash
Flood Watch for portions of southeast Arizona. Daily high
temperatures will fluctuate between near normal and a few degrees
below normal.

&&

.DISCUSSION...The Excessive Rainfall Outlook through Thursday
depicts portions of southeast Arizona in a slight risk (level 2 of
4) equating to a 25 percent chance of excessive rainfall leading to
flash flooding within 15 miles of a point. Over the past 72 hours,
we've seen flowing washes and rivers after 1 to 2 inches of rain has
fallen in some locales providing saturated soils and flashy
antecedent conditions for any additional rainfall.

For today, the slight risk for excessive rainfall is centered on
areas from the Tucson Metro eastward. As of this writing, showers
and storms are already forming in moisture rich airmass with robust
instability and will likely become more widespread over the next few
hours as a mesoscale convective system drifts north over Sonora
Mexico providing additional forcing. In this juicy environment,
storms this afternoon and evening will be capable of producing
rainfall rates of 1-2 inches per hour with a slight chance for
locally higher rates under any of the stronger cells that cluster.
Flash Flood Watch continues through 11 PM MST this evening.
Potential impacts/hazards include urban and street flooding, water
running through normally dry washes, and low water crossings
becoming inundated and impassable. Overnight some of the CAMs are
showing nocturnal activity continuing thus, chances for showers and
storms (20-50%) continue overnight. Something to keep an eye on.

While tomorrow does still appear to be a relative down day, storms
today and tonight will likely play a role in the coverage and/or
timing of storms tomorrow. That being said, any storms that form
will again have the potential for locally heavy rainfall rates
upwards of 1 to 2 inches per hour. Slight risk for excessive
rainfall resulting in flash flooding continues centered from the
Tucson Metro east.

Wednesday is looking to be another more active day with scattered to
numerous thunderstorms as an upper level disturbance moves north out
of Sonora Mexico and across southeast Arizona. The disturbance will
add additional upper level support ultimately helping air rise in an
environment with precipitable water content around 150-250% of
normal for this time of year. Storms will be capable of producing
heavy rainfall rates, although the specific timing/positioning of
the disturbance relative to the best instability could drive where
storms specifically form initially and grow upscale.

Thursday: Similar to Tuesday in that it is still looking not quite
as active as Wednesday as forcing from the disturbance that comes
through on Wednesday will move out of the area. But with plenty of
moisture around, any storms that do form will again be capable of
heavy rainfall. Slight risk for excessive rainfall resulting in
flash flooding continues from Tucson eastward.

Friday into this weekend: Drier air finally pushes into southeast
Arizona from the west as our flow aloft turns westerly. Chances for
precipitation (10-40%) continue, but with drier air aloft, we will
see less heavy rainfall. Looking like the best chances will remain
east and south of Tucson.

8 to 14 day outlooks (Mon Sep 21 to Sun Sep 27)
Temperature: Leaning above normal, 44-45% chance
Precipitation: Likely above, 49-52% chance

&&

.AVIATION...Valid thru 16/00Z.
SCT-BKN clouds 7k-10k ft AGL for much of valid pd with layers clouds
above. SCT-NUM SHRA/TSRA thru 15/04Z becoming ISOLD-SCT thru the end
of the valid pd. Outflow winds near TSRA of 35-45 kts. VSBYs down to
1SM nr strongest TS. SFC winds SWLY/SWLY at 6-10 kts thru 15/04Z and
again after 16/17Z. At other times, SFC winds terrain driven and
less than 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...
Flood Watch through 11 PM MST this evening for AZZ503>509-511>514.

&&

DVS

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