104
FXUS65 KTWC 232013
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
114 PM MST Sat Aug 23 2025

.SYNOPSIS...Shower and thunderstorm chances continue this
weekend west of Tucson, then expand to the remainder of southeast
Arizona starting Monday. Expect daily chances for showers and
thunderstorms with day to day variability on coverage and intensity
next week. Above normal temperatures through the weekend and then
trending down to near normal by the start of next week. An Extreme
Heat Warning in effect until Sunday evening for the greater Tucson
area to southeastern Pinal county.

&&

.DISCUSSION...Latest visible satellite imagery shows partly cloudy
skies across most of southeast Arizona as a cumulus field has
developed. Moisture levels vary considerably from east to west
across our forecast area with PWAT values 0.5 inches to 0.7 inches
across Cochise/Graham/Greenlee Counties with a much wetter
atmosphere across central and western Pima Counties where PWAT
values are 1.25 inches to 1.5 inches. The 18Z KTWC sounding came in
with a PWAT of 0.86 inches as the shallow lower level moisture has
rapidly mixed out over the last several hours with surface dewpoints
crashing to 42 degrees on the most recent KTUS observation. The
sounding also reveals very dry air above 700mb and a lack of
instability so confidence is high that locales from Tucson eastward
stay dry today. However, across central and western Pima County,
where the moisture is deeper, we do expect scattered showers and
thunderstorms to develop this afternoon. These will produce strong
to locally severe threshold winds (DCAPE is 1500-1800 J/KG) and
locally heavy rainfall under the stronger storm cores. While the
bulk of the activity will diminish this evening, a few showers and
thunderstorms may linger overnight west of Tucson.

The forecast for Sunday is very similar to today. Mid/upper level
high pressure will be near the AZ/NM border with a continuation of
easterly flow across southern Arizona. Drier air remains in place
from Tucson eastward while the western deserts continue to see
higher moisture levels from the Gulf of California and Sonora. This
will result in a continuation of afternoon and evening shower and
thunderstorm chances west of Tucson with strong to severe
thunderstorms across far western Pima County where the HREF has 10-
30% neighborhood probabilities (40-km) of winds greater than 50 kts.
Otherwise, temperatures will remain above normal for this time of
year through Sunday and an Extreme Heat Warning remains in effect
for portions of eastern Pima and SE Pinal Counties.

As the mid/upper level high shifts eastward starting Monday and a
trough develops off the west coast this will place our forecast
under under more southerly flow. Starting Monday there will be an
expansion of shower and thunderstorm chances eastward to include
Tucson and the entire forecast area. Given the deeper moisture plume
(more widespread PWAT`s around 1.5 inches) is progged to remain
across our area through Wednesday, thunderstorms chances remain
elevated through mid week. Still considerable uncertainty though on
the specifics on a daily basis this far out. Temperatures will cool
down to below normal levels starting Tuesday. A gradual drying trend
should start Thursday and continue into Saturday as some westerly
flow tries to reassert itself.

&&

.AVIATION...Valid through 25/00Z.
SCT 9k-12k ft AGL with ISOLD -SHRA/-TSRA west of KTUS mainly thru
24/04Z and once again aft 24/19Z.  SFC winds will generally be E-SE
less than 12 kts through the forecast period. Expect gusty and
erratic winds with any -TSRA. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Expect daily chances for rain showers and
thunderstorms into next week with day to day variability of
intensity and coverage of storms. Temperatures will be running
above normal this weekend with an Extreme Heat Warning in effect
for the lower elevations. Winds will generally remain less than
15 mph with the afternoon gustiness into next week. Min RHs will
be 15-20 percent in the low elevations and 20-30 percent in the
mountains through the weekend. Deep monsoon moisture will return
early next week to provide higher wetting rain chances and
coverage as well as better min RHs and below normal temperatures.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Extreme Heat Warning until 8 PM MST Sunday for AZZ504>506.

&&

$$

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