921
FXUS65 KTWC 152157
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
257 PM MST Sat Aug 15 2026

.SYNOPSIS...Expect a slight chance of afternoon thunderstorms
today as the combination of drier-air and a more stable
atmosphere aloft will limit thunderstorm activity across all of
Southeast Arizona. Hot conditions will return next week with an
Extreme Heat Warning in effect for portions of Southeast
Arizona Monday though Friday of next week. A more active
thunderstorm pattern has the potential to return the second half
of next week.

&&

.DISCUSSION...Aloft high pressure is centered well to the east
over Louisiana putting southeast Arizona under southwesterly
flow. There is also an easterly wave centered just southeast of
Big Bend. The southwesterly flow has led to a decrease in
moisture with GOES East total precipitable water ranging from
1.25" in western Pima County to 0.95" along the AZ/NM border.
Still enough moisture for isolated storms mainly over the higher
terrain south and east of Tucson as evidenced on current radar
and satellite. Expect this isolated activity to continue through
the afternoon and evening. Sunday the ridge starts to expand
further westward and the easterly wave moves into northern
Chihuahua. This will lead to a couple degree increase in
temperatures compared to today. CAMs show thunderstorm activity
to be similar to today with isolated activity south and east of
Tucson.

Early to mid next week the ridge becomes centered over Arizona
leading to temperatures 5-8 degrees above normal through at
least Friday. This will lead to areas of Major HeatRisk across
portions of southeast Arizona. An Extreme Heat Warning is in
place for Pima County, Pinal County, and portions of Graham and
Greenlee Counties Monday-Friday.

Moisture will continue to be around normal to a bit below normal
for this time of year this week. Monday will likely see an
uptick in activity east of Tucson, especially in Cochise County,
as the aforementioned easterly wave moves through far northern
Sonora. Even with the meager moisture, expect isolated to
scattered thunderstorms in the afternoon and evening with storms
capable of locally heavy rainfall and strong wind gusts.
Tuesday and Wednesday NBM PoPs are 20-40 percent over the White
Mountains and south and west of Tucson. Thursday and Friday the
high lifts a little further north putting southeast Arizona
under more favorable easterly flow. However ensembles are
pessimistic with moisture returns, keeping PWATs around normal.
This is likely because the flow around the high is compressed
thanks to a trough in the Midwest. The easterly fetch of winds
does not reach moisture rich areas near the Gulf of Mexico. The
flow around the eastern periphery of the high turns north over
central Texas into the Great Plains, which doesn`t allow as deep
of moisture to advect in. Even with this still expect an uptick
in thunderstorm activity as models also show mid-level flow
20-25 kts. And if the upper air pattern changes to allow a
longer fetch of easterlies, better moisture can move in, which
would increase storm chances and coverage.

&&

.AVIATION...Valid through 17/00Z.
FEW-SCT 10-14k ceilings with cumulus development this afternoon.
Slight chance of -SHRA/-TSRA centered mainly over higher
terrain through around 16/02Z. Gusty and erratic winds possible
near TSRA with gusts to 35 kts. Otherwise surface winds west to
northwest 7-12 kts with occasional gusts to 20 kts, then light
and terrain driven after 16/02Z. Winds remain light through
Sunday. Just slight chances for -SHRA/-TSRA again Sunday
afternoon. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...A slight chance of storms this weekend focused
mainly south and east of Tucson and over the higher terrain. A
more active monsoon pattern looks to return around the middle of
next week. Minimum relative humidity will be 20-35 percent
today lowering to around 15-30 percent thereafter. Temperatures
will warm-up to above normal by Sunday and persist well into
next week. Outside of thunderstorms, winds will be terrain
driven around 10 mph with occasional afternoon gusts to 20 mph.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Extreme Heat Warning from 10 AM Monday to 8 PM MST Friday for
AZZ501-502-504>506-509.

&&

$$

Hardin

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