874
FXUS65 KTWC 032130
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
230 PM MST Wed Sep 3 2025

.SYNOPSIS...Scattered thunderstorms this evening and again
Thursday afternoon before deeper tropical moisture pushes in late
Thursday into Saturday bringing periods of heavy rain and
increased likelihood for flash flooding. High temperatures Friday
and Saturday will be well below normal. Dry conditions arrive
next week as well as a return to near normal temperatures.

&&

.DISCUSSION...Afternoon satellite imagery showed partly cloudy
conditions from Tucson east while it was mostly sunny west.
Convection has been slow to start this afternoon with overall
trend for scattered showers and thunderstorms mostly west of
Tucson. Main threat will be gusty winds and locally heavy rain.

Tomorrow will see the first influx of moisture from Lorena with
scattered showers and thunderstorms mostly occurring from Tucson
west. Main threat again will be gusty winds and locally heavy
rain. Latest HREF neighborhood probabilities has 10% chance of
3+ inches across western Pima county. Highs running around 10
degrees below normal.

All eyes continue to be focused on how much rainfall the area
will see from the moisture influx from Hurricane Lorena which was
located this afternoon about 145 miles west of Cabo San Lucas,
Mexico. Little change was made to the track as circulation crosses
Baja near the Spur Friday then moving into Sonora Saturday AM as
a depression. There continues to be considerable uncertainty on
how much and where the heaviest rainfall will occur Friday into
Saturday. Here are some scenarios:

Low end (9 in 10 chance): totals mostly less than 1" area wide,

High end (1 in 10 chance): totals ranging from 1" to 5", with the
highest amounts along the Intl border from Nogales west and in
the mountains,

Current forecast from WPC: totals ranging from 0.50" to 3"+.

A Flood Watch has been issued from areas south and east of a
Clifton to Dudleyville to Marana to Sasabe. See hydrology section
below on potential increased flow in the Santa Cruz and San Pedro
rivers.

Due to cloud cover and showers, highs will struggle to get out of
the 60s and 70s. For example, GFS MOS for Tucson Friday has a high
of 73 degrees. Current NBM guidance likely a bit to warm.

Conditions dry out late Saturday into Sunday with temperatures
warming up. Next week dry with highs near or slightly above
normal under westerly flow aloft.

&&

.AVIATION...Valid through 05/00Z.
SCT -SHRA/-TSRA west of KTUS thru 04/04Z and then again after
04/19Z. Gusty winds up to 45 kts possible with any thunderstorm
along with heavy rain. Otherwise light winds generally under 12
kts. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Driest minimum relative humidities today will be
in the Gila River Valley with 15-18 percent values this
afternoon. Otherwise humidities generally above 20-30 percent
across southeastern Arizona. Winds today will be light and terrain
driven. Scattered thunderstorms with chances for wetting rain
possible for Santa Cruz, Pima, and Pinal counties, as well as the
White Mountains. Moisture will increase further over the coming
days bringing daily widespread chances for showers and
thunderstorms through Saturday.

&&

.HYDROLOGY...The latest QPF forecast from WPC for late Thursday
into Saturday has a large swath of 1" to 3" of rain with up to 4"
possible on the headwaters of the Santa Cruz and San Pedro Rivers.
Latest model runs by CBRFC has some locations along the Santa Cruz
River in Santa Cruz county and the San Pedro River in Cochise
county approaching or exceeding action or bankfull stage. Still
some uncertainty on amount of rainfall that will be associated
with the remnants of Lorena. Flash Watch is in effect for much of
southeast Arizona from 12 noon Friday through 5 pm Saturday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Flood Watch from Friday afternoon through Saturday afternoon for
  AZZ503-504-506>514.

&&

$$

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