Forecast Discussion

Forecast Discussion for TWC NWS Office
046
FXUS65 KTWC 022242
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
342 PM MST Tue Sep 2 2025

.SYNOPSIS...Scattered thunderstorms expected this afternoon mainly
from Santa Cruz county through central and western Pima county. A
few may develop over the White Mountains as well. Heavy rain with a
threat of flash flooding will be the main hazard with any
thunderstorm in Santa Cruz and Pima counties today. Additional
thunderstorm chances are expected Wednesday. Then Thursday into the
weekend precipitation chances will increase as tropical moisture
moves into southeastern Arizona. High temperatures will be near
normal through Wednesday, then will become below normal the second
half of the week.

&&

.DISCUSSION...Scattered showers and thunderstorms have formed over
western and central Pima County as of this writing with additional
cloud and storm development over the same areas. Training showers
and thunderstorms will continue this afternoon and evening across
Pima and Santa Cruz counties in an unstable atmosphere with high
precipitable water (PW) content. Isolated to widely scattered
instances of flash flooding are possible, and the Weather Prediction
Center (WPC) has depicted a slight risk (15%) for excessive rainfall
which may result in isolated to widely scattered instances of flash
flooding. While the primary threat will be focused on heavy rainfall
rather than wind, cannot rule out a few locally enhanced outflows
(winds gusts around 35-45 mph) resulting in minor blowing dust
impacts.

Looking ahead to tomorrow, expect similar storm coverage with heavy
rainfall being the chief concern again. However, high resolution
guidance shows storms first forming a bit more south and east on
higher terrain in Santa Cruz county compared to today before pushing
gradually west and north. Drier air to the east should limit
shower and storm formation to the east along the New Mexico
border.

Thursday through Saturday richer tropical moisture will move into
southern Arizona thanks to Tropical Storm Lorena. The trajectory of
Lorena remains rather uncertain. Regardless of the track, even a
modest moisture increase could be impactful as the atmosphere will
be more conducive to flash flooding. Still keeping an eye on
forecast trends to narrow down potential rainfall amounts and
associated impacts.

&&

.AVIATION...Valid through 04/00Z.
SCT-BKN 9k-12k feet. Scattered TSRA west of KOLS-KTUS-KAVQ through
03/04Z. SFC winds SELY at 9-14 kts becoming WLY to SWLY at KTUS and
KOLS after 03/03Z. Gusts up to 40 kts possible near TSRA. Tomorrow,
SFC winds SELY to SWLY at 7-12 kts. Scattered thunderstorms again
after 03/18Z. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Minimum relative humidity values will be driest in
the Gila River Valley this afternoon and Wednesday, then increasing
above 25-35 percent the remainder of the week. Humidity will be
mainly above 20-30 percent elsewhere this week, especially Thursday
through Saturday as a substantial increase in moisture arrives.
Southeasterly winds today strongest through the Gila and
southeastern Cochise at 13 to 18 mph with gusts to 30 mph. 10-15 mph
elsewhere from Tucson to Nogales west. Scattered thunderstorms will
continue this afternoon from Santa Cruz through central and western
Pima. A few may also develop over the White Mountains. Additional
chances again on Wednesday, then increasing chances across
southeastern Arizona to end the week as moisture moves in.

&&

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

&&

$$

DVS

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NWS TWC Office Area Forecast Discussion