335
FXUS65 KTWC 080800
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
100 AM MST Tue Sep 8 2026

.SYNOPSIS...Isolated to widely scattered thunderstorms this
afternoon and this evening, especially along the International
Border to the southeast of Tucson. A more active thunderstorm
pattern for Southeast Arizona develops Wednesday into Thursday.
The primary hazard with these storms will be heavy rainfall
leading to localized flash flooding with a secondary hazard of
strong outflow winds. High temperatures will will fluctuate
between near normal and a few degrees below normal.

&&

.DISCUSSION...The upper pattern this morning is defined by a
strong ridge of high pressure extending from eastern New Mexico
into western Illinois, with a high center positioned over ERN
Kansas. The latest GOES precipitable water imagery indicated the
deeper moisture resides from Tucson west (PWATs between 1.50 and
1.75 inches) and NW Sonora Mexico with generally drier air with
PWAT values 1.30 to 1.50 inches to the east of Tucson into SW
New Mexico and NW Chihuahua MX.

An inverted positioned along the base of the upper ridge this
morning will track west today amplifying the flow and resulting
in a secondary high center developing over southern New Mexico
by 09/00Z this afternoon. Not much large scale lift across
Southeast Arizona today as the upper ridge nudges into the area
from the east, but there is a small area of deformation aloft
that develop along the International Border SE of Tucson. The
lack of mid-level flow will result in mainly mainly isolated
pulse-type thunderstorms today with the primary hazard being
localized heavy rain due to the fact PWATs are approximately
130-150% of normal for this time of year.

I think the primary weather focus should be on Wednesday (and
to a lesser extent Thursday) since the days that are the most
active usually occur when the upper high center is on the move.
The upper high center is progged to move into central Arizona by
10/00Z Wednesday afternoon then WRN AZ by 10/06Z. This movement
results in an area of decent stretching deformation/lifting
mechanism aloft across Southeast Arizona while also providing a
favored rim-shot pattern to move storms from the Mogollon Rim SW
toward the Tucson Metro Area. The presence of 25-30 kts of
0-6km AGL Bulk Shear Wednesday evening across the eastern half
of the forecast area will help organize and cluster storms as
they move into eastern Pima county. Deeper moisture moving into
Pima/SE Pinal and Santa Cruz counties from NW Sonora Mexico
during the day Wednesday will provide the potential for heavy
rainfall/isolated flash flooding. Could be an interesting day.

Otherwise, we will maintain enough moisture across the region
for mainly scattered afternoon and early evening thunderstorms
this weekend into early next week. The Monsoon season rolls-on.

&&

.AVIATION... Valid thru 09/12Z. SCT to BKN clouds 10-15k ft AGL
through 08/20Z, then SCT-BKN 8-10k ft AGL BKN-OVC 12-15k ft AGL
this afternoon into the early evening. Isolated SHRA/TSRA along
the International Border and AZ/NM border from 08/20Z thru
09/03Z with localized thunderstorm outflow winds to 30 kts
possible. Otherwise, SFC winds will generally be less than 12
kts and terrain driven this morning, becoming SWLY 10-15 kts
during the afternoon. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Isolated to widely scattered thunderstorms this
afternoon and this evening, especially along the International
Border to the southeast of Tucson. A more active thunderstorm
pattern for Southeast Arizona develops Wednesday into Thursday.
The primary hazard with these storms will be heavy rainfall
leading to localized flash flooding with a secondary hazard of
strong outflow winds. Temperatures will be around normal to a
few degrees below normal into early next week. Minimum relative
humidity values mainly 20 to 45 percent in the valleys and 30 to
60 percent in the mountains over the next week. Winds will
generally remain less than 15 mph and terrain driven through the
week.

&&

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

&&

$$

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