Flash Flood Warning 54, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
239 PM MST Wed Sep 17 2025

.SYNOPSIS...Moisture has moved into the region which will lead to
scattered showers and thunderstorms through the end of the work week
with gradually diminishing thunderstorm chances over the weekend.
Temperatures near to just below normal into the weekend before
warmer and drier weather returns next week.

&&

.KEY MESSAGES...

- Isolated to widely scattered showers and thunderstorms this
  afternoon with heavy rainfall may result in localized instances
  of flash flooding, mainly west and south of Tucson.

- Increasing chances (40-60%) for isolated showers and storms
  becoming scattered in the afternoon to early evening hours.
  Isolated instances of flash flooding possible.

- Chances (30-60%) for showers and thunderstorms with heavy rain
  continue on Friday, but decrease over the weekend with high
  temperatures returning to near triple digits for the Tucson
  Metro by the start of next week.

&&

.DISCUSSION...Isolated slow moving showers and storms have been
developing first over the higher terrain areas across southeast
Arizona mainly south and west of Tucson. Clouds have thinned enough
for the atmosphere to destabilize, eroding away convective
inhibition, especially to the south and west of Tucson. This is
also where better moisture resides with precipitable water over
1.5". The KTWC 17/18Z sounding measured 1.4" of precipitable water
continuing to support the solution that any storms that form
today are in an environment that favors flash flooding rather than
wind, especially west and south of Tucson.

Tomorrow into tomorrow evening chances (30-60%) for scattered
showers and thunderstorms will continue across southeast Arizona
with above normal precipitable water in place from the now post
tropical cyclone Mario located off the coast of Baja California. The
potential for heavier rain will expand north and eastward as a
modestly strong upper level jet aids synoptic scale support for
ascent in addition to localized terrain forcing. Like today, storms
will first tend to remain isolated firing off the higher terrain
areas. However, anticipate storms to become more scattered in the
mid to late afternoon and early evening hours and push off the
mountains. The biggest limiting factor as of now continues to be
residual cloud cover.

Chances (30-60%) for scattered showers and storms continue again
on Friday with a continued threat for localized heavy rainfall.
Over the weekend, precipitation chances begin to decrease as the
Monsoon high circulation nudges north putting southeast Arizona in
a westerly flow pattern. Consequently, a gradual warming and
drying trend is expected with high temperatures rebounding to near
100 degrees heading into next week for the Tucson Metro and
points west.

&&

.AVIATION...Valid through 19/00Z.
BKN-OVC clouds 6k-10k ft AGL and BKN-OVC layer AOA 18k ft AGL thru
the valid period. Scattered TSRA possible through 18/04Z. Best
chances will be at KDUG and KOLS terminals. With showers and
thunderstorms, expect locally heavy rainfall and erratic winds up to
35 kts. Other than thunderstorm driven winds, SFC winds will be from
the south southwest 5-10 kts in the afternoon and evening becoming
variable less than 7 kts at other times. Tomorrow, scattered TSRA
possible again after 18/19Z. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Above normal moisture this week leading to min RH
between 20-40 percent through the weekend. Expect scattered shower
and thunderstorm chances (30-60 pct chance) each day through Friday,
then diminished thunderstorm chances this weekend. Dry conditions
return next week. 20-foot winds will be 8-12 mph with some
afternoon/early evening gusts to around 20 mph over the next week
with normal diurnal patterns through the weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

DVS

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