249
FXUS65 KTWC 160826
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
126 AM MST Sat Aug 16 2025

.SYNOPSIS....Isolated to scattered thunderstorms today across
Southeast Arizona. Given the ample atmospheric moisture available
for these storms, the main impact with these storms will be the
potential for locally heavy rainfall, especially southeast of
Tucson in Cochise county. Otherwise, daily isolated to scattered
showers and thunderstorms will persist into next week with day to
day variability in intensity and chances.

&&

.DISCUSSION...The upper pattern this morning is defined by a
trough of low pressure across California and the Great Basin, and
an upper ridge (500-300 mb) of high pressure over Oklahoma
extending into west north Texas. The SSW flow aloft across
Southeast Arizona this morning begins to shift to the SW today as
the upper ridge begins to drift SW into west Texas/northeast
Chihuahua Mexico. The latest GOES Total Precipitable Water imagery
indicated a plume of PWATs between 1.25 and 1.45 inches extending
across the majority of Southeast Arizona to the northwest into
Maricopa county. This matches up with the PW value of 1.34 inches
on the 16/00Z KTWC upper air sounding. Although there is a lack of
forcing aloft to aid thunderstorm development today, there is
plenty of moisture around for more typical isolated to scattered
thunderstorms across the CWA, especially from Tucson southeast
and east. Given the ample moisture, these storms will be capable
of producing locally heavy rainfall. The 16/00Z HREF indicated a
50% neighborhood (40-km) probability on their 3-hr ensemble
probability matched mean QPF of rainfall in excess of 1.00 inch
across Cochise county this afternoon.

Otherwise, the upper high slowly shifts into southern New Mexico
Sunday afternoon, the AZ/NM border by Monday afternoon, then on
its way to the Four Corners region Tuesday afternoon. It then
resides there and strengthens the second half of next week.
Although this location is usually active for our neck of the
woods, it all depends on the moisture that is available. The
16/00Z deterministic GFS indicated a plume of high precipitable
water values (1.50+ inches) moving up the Gulf of California into
the lower deserts of SW Arizona begining Monday. Unfortunately we
also see a general drying across the eastern half of our forecast
area to below an inch of PW the second half of next week. This
will likely set-up a pattern where we have isolated storms east of
Tucson capable of producing strong and gusty thunderstorm
outflows but little rainfall...moving west to southwest across the
CWA, increasing in coverage and becoming capable of producing
heavy rainfall the farther west the storms make it. The bigger
story may end up being the increasing afternoon high temperatures
warming back up to 4-6 degrees above normal Wednesday through
Friday of next week.

&&

.AVIATION...Valid through 17/12Z. SCT clouds AOA 10k to 14k ft AGL
through 16/14Z, then SCT-BKN 7-10k ft AGL with ISOLD-SCT -SHRA/-TSRA
between 16/19Z and 17/03Z. Although gusty and erratic winds 35
kts will be possible near any TS, surface winds should remain
below 15 knots with the occasional afternoon gusts up to 20 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Expect daily chances for thunderstorms and wetting
rain showers into next week. Min RHs will generally be around 25
percent in the lower elevations and 45+ percent in the mountains
today. Sunday, min RHs will start to drop back down to the 15-20
percent in the lower locations and 20-30 in the mountains into the
new week. Winds will generally be less than 15 mph with typical
afternoon gusts up to 20 mph into next week. Monsoon moisture is
projected to return late next week to provide higher chances for
thunderstorms and rain showers. Temperatures will be around normal
through this weekend, trending above normal the second half of
next week.

&&

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

&&

$$

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