954
FXUS65 KTWC 312102
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
202 PM MST Sun Aug 31 2025

.SYNOPSIS...Isolated to scattered thunderstorms are expected to
develop this afternoon and evening, mainly south and east of
Tucson. Thunderstorm outflows could move through Tucson this
evening leading to the potential for isolated thunderstorms.
Gusty thunderstorm winds may produce blowing dust at times. Shower
and thunderstorm chances continue through the coming week with
day to day variability. High temperatures will be near normal
through mid- week, then become below normal the second half of the
week.

&&

.DISCUSSION...Isolated thunderstorms have formed over the Gila in
New Mexico and southern Greenlee County. This thunderstorm
activity will expand westward and southward this afternoon and
evening. Hi-res models also show isolated to scattered storm
coverage over Santa Cruz County and southern Cochise Counties.
High pressure will be centered just to the north of the CWA
putting most of the area under east to northeast flow aloft. This
will set up an opportunity for a rim shot late this afternoon into
the evening. The last few runs of the HRRR have shown storms
moving off the rim pushing an outflow into Graham and Cochise
Counties around 4-6 PM, potentially reaching Tucson by 7-9 PM, and
then Sierra Vista 8-10 PM. The 31/18Z Tucson sounding isn`t very
conducive to thunderstorm development, but an outflow could
produce enough mechanical lift for some thunderstorms this
evening. Main threat with storms today will be gusty winds
especially in the Gila River Valley and I-10 corridor in Cochise
County. The HREF is highlighting this area for highest
probabilities for strong winds today. The HREF has a 20-35 percent
chance for winds 45 mph or greater within 25 miles of a point
from Safford down to Wilcox and east to San Simon. Blowing dust
will be possible as the outflows move through. Localized heavy
rain could also be a threat but will be secondary to strong
outflow winds.

Monday storm chances expand westward as moisture moves into
western Pima County. Areas east of Tucson will begin to dry out a
little but will still see a 20-30 percent chance for thunderstorms.
The NAM and the GFS bring an easterly wave through northern
Sonora Monday afternoon which could enhance thunderstorm activity
along the international border and western Pima County. Still some
uncertainty with its exact north/south placement. HREF members
show storms forming over the rim again along with south and west
of Tucson. However on the rim winds will be easterly instead of
northeasterly like today, which leads to storms moving into Pinal
and Maricopa Counties rather than Graham and Cochise Counties.
Main threats will again be strong outflow winds and localized
heavy rainfall.

Tuesday and Wednesday mid-level flow stays easterly to southerly
keeping a steady stream of moisture in place west of Tucson with
further drying east of Tucson. Both days storm chances (30-40
percent) will be greatest west and south of Tucson and in the
White Mountains. Tucson will be on the eastern edge of storm
chances and could see isolated activity each day. Thursday into
Saturday storm chances increase area wide thanks to the potential
influx of tropical moisture. The current NHC forecast has an 80
percent chance of tropical storm formation over the next 7 days
off the west coast of Mexico and southern Baja. The main
question is where the tropical system will go once it approaches
Baja. The ECMWF keeps it further west a few hundred miles off the
west coast of Baja and the GEFS keeps it closer to Baja,
potentially bringing it across the Gulf of California into
southern Sonora. Right now NBM PoPs Thursday into Saturday are
30-60 percent across the CWA.

&&

.AVIATION...Valid through 02/00Z.
Isolated to scattered thunderstorms thunderstorms this afternoon,
mainly south and east of KTUS. Coverage more likely near KSAD-
KDUG-KOLS late this afternoon and evening. Gusty outflow winds up
to 40 kts possible with any thunderstorm. The HRRR is showing the
potential for an outflow boundary starting near KSAD this
afternoon moving southwestward and getting to KTUS around 01/04Z,
which could bring TSRA. Confidence is low on the thunderstorm
chances, but high on the outflow changing winds to
easterly/northeasterly with gusts up to 30 kts between
01/04Z-01/07Z at KTUS. Outside of thunderstorms sfc winds will be
northerly 8-12 kts this afternoon and early evening at KTUS, and
easterly at terminals south and east of Tucson. KTUS will turn
easterly once the outflow moves through around 01/04Z. Aviation
discussion not updated for TAF Amendments.

&&

.FIRE WEATHER...Moisture increases east of Tucson today and
across southeastern Arizona Monday, with minimum relative humidity
values above 20 percent becoming widespread Monday. Daily chances
for thunderstorms through this week with this increase in
moisture, with day to day variability. Gusty outflow winds
possible with any thunderstorm. East to southeast winds of 12-17
mph develop Monday, potentially lingering through Tuesday.

&&

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

$$

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