891
FXUS65 KTWC 260900
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
200 AM MST Wed Aug 26 2026

.SYNOPSIS...A very low grade monsoon pattern continues today with
limited (10 percent or less) storm chances for most locales. Storm
chances nudge higher starting Thursday (10 to 20 percent), with a
more active monsoon pattern looking to setup Friday through Monday.
High temperatures will remain well above normal through the week
with an Extreme Heat Warning in effect for much of southeast Arizona.

&&

.DISCUSSION...Clear skies across southeast Arizona this morning as
strong high pressure aloft over western New Mexico is the dominant
feature of our weather pattern. Moisture levels are below normal
across the region, but most notably from Tucson eastward with PWAT
values 0.7" to 0.9" at this time, with surface dewpoints mostly in
the 40s to lower 50s. A bit more moisture west of Tucson where PWATs
range from 1 to 1.2 inches. Storm activity will struggle once again
today as the strong high nudging west to the AZ/NM border results in
broad subsidence (with dry air aloft). Can`t rule out a storm or two
mainly to the south to southwest of Tucson from Santa Cruz into
south central Pima County where moisture and instability levels are
more supportive and the subsidence under the high isn`t as
pronounced. The hottest temperatures of this extended heat stretch
are expected today, with the current forecast of 109 degrees in
Tucson. Wouldn`t be surprised if it ends up slightly higher (110 or
111) if stronger mixing of drier air aloft occurs dropping surface
dewpoints aiding surface heating.

While there won`t be much change with the mid/upper level high on
Thursday, centered near or just west of the AZ/NM border, lower
level moisture will start to be on the increase. This will begin to
occur late tonight/Thursday morning as a likely first modest push of
moisture occurs courtesy of outflow from convection in Sonora. This
will set the stage for a few more storms (mostly 10 to 20 percent
chance) on Thursday with the focus still on locales south to
southwest of Tucson. Wind will be the primary concern with any
storms on Thursday.

From Friday through Monday, we will quickly transition into a much
more active monsoon pattern. During this time, the mid/upper level
high will be on the move eastward into a more favorable position
over New Mexico by Saturday, with the stage being set for broader
deep layer southeast to southerly flow. This will result in
sustained above normal moisture with 110 to 150 percent of normal
PWAT values. Troughing over the NW part of the state could also
provide a little bit of additional lift especially Sunday/Monday.
Bottom line is this will translate into storm chances in the 20 to
50 percent range Friday increasing to 30 to 60 percent Saturday
through Monday. As is usual for the monsoon, we will likely have a
more `up` day or two but it`s too far out to really get a good feel
for the most active days. As deeper moisture moves in, we`ll also be
adding increased flash flooding potential in addition to wind
threats. Thereafter, back to a more typical lower to mid to start
the month of September but still considerable uncertainty that far
out.

The Extreme Heat Warning remains in effect through Saturday.
Admittedly, temperatures on Saturday are expected to drop a few
degrees compared to today through Friday. We`ll continue to monitor
that for any later adjustments in the timing of the Extreme Heat
Warning. By Sunday into early next week, temperatures drop to more
seasonable levels.


 &&

.AVIATION...Valid through 27/12Z. SKC-SCT clouds mainly 10-13k ft
AGL through the forecast period with slight chance of -SHRA/-TSRA
for points near and west of KOLS between 26/21Z and 27/03Z. Surface
winds mainly light and terrain driven with occasional afternoon
gusts around 15 kts Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Very isolated thunderstorms (10 percent or less
chance) for most locales today. Storm chances nudge higher to around
10 to 30 percent Thursday, with a more active pattern taking hold as
early as Friday but especially this weekend through Monday (30 to 60
percent daily chance). Temperatures will remain well above normal
through most of the week with a cooling trend this weekend into
early next week. Minimum relative humidity values mainly 10 to 20
percent in the valleys and 20 to 30 percent in the mountains through
Friday. Minimum RH values increase to 20 to 40 percent starting
Saturday in valleys and 30 to 50 percent in the mountains. Winds
will generally remain less than 15 mph and terrain driven through
the week.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning until 8 PM MST Saturday for AZZ501>509.

&&

$$

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