744
FXUS65 KTWC 300942
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
242 AM MST Fri Oct 30 2026

.SYNOPSIS...Scattered showers and thunderstorms this morning,
becoming more numerous across the region this afternoon and
persisting into the evening. Saturday will see a lull in
precipitation, though slight chances (10 percent) of showers
persist. Another weather system will bring widespread showers with
scattered thunderstorms Sunday into Monday. A Flood Watch has been
issued for most of Pima county, Pinal county, Santa Cruz county,
Graham county, and Greenlee county from 11 PM Saturday through 5 AM
Monday.

&&

.DISCUSSION...A busy weather pattern through the weekend for
southeast Arizona. The upper air pattern currently features
southwesterly flow as an active subtropical jet pattern takes hold.
The first of two significant weather systems will impact southeast
Arizona today. A pre-cursor disturbance has already resulted in
scattered showers and thunderstorms last night, with showers and
thunderstorms persisting early this morning as broader lift
increases across the region under broad diffluent flow and
increasing 850-700mb moisture convergence. In the last hour a round
of thunderstorms moved through Tucson producing a quick localized
0.5" to 1 inch of rain and some small hail. Latest SPC mesoanalysis
shows MUCAPE around 1000 J/KG helping to support elevated
convection. CAMs have really struggled this morning picking up on
any of this activity, so have made short term modifications to the
forecast to maintain scattered showers and thunderstorms through the
morning hours before more widespread shower and thunderstorm
activity moves in this afternoon. This activity will be aided by the
combination of broad scale lift in the left front quadrant of the
250mb jet and deep lower level moisture with strong 850-700mb
moisture convergence. Still some uncertainty in terms of just how
much solar insolation we`ll see to increase surface based
instability but should be enough warming to generate around 500-1000
J/KG of SBCAPE which combined with modest 0-6km bulk shear around 30
kts will be enough to result in the potential for a few stronger to
marginally severe thunderstorms. SPC continues to outline our area
in a marginal risk today for severe thunderstorms with strong wind
gusts and hail the main threats. We`re also in a marginal risk from
WPC for excessive rain north of Tucson today. The most common
additional rain amounts today through this evening will be 0.25" to
0.75", though given the convective nature of the precipitation, some
areas will see less and others more. Higher precipitation amounts
can be expected in areas that see repeating rounds of thunderstorms
which is most likely north to northeast of Tucson. In this case,
isolated areas of 1 to 2 inches of rain (with isolated flash
flooding as well) are expected with the probability of 1 inch or
more of rain averaging about 20 percent for any single location.

While the area remains under southwesterly flow aloft on Saturday,
we`ll generally be between systems with limited large scale lift.
However, given the moisture still in place (0.75" to 1" PWAT),
isolated shower activity is expected (10 to 20 percent chances
during the day), with any precipitation short lived under individual
showers. Thereafter, more widespread rain chances start to ramp up
as the evening progresses Saturday night on the leading edge of the
next more significant weather system.

A more potent subtropical weather system the moves into and through
our region Sunday through Sunday night. This will bring near record
to record levels of PWAT for this time of year (1.25" to 1.50") or
about 5 standard deviations above normal. IVT values also peak at
around 750 which is a level 3 on the AR scale, though this is
tempered by the short residence time of the AR. What this all boils
down to on Sunday is the expectation for widespread shower activity
with isolated embedded thunderstorms. Given the stronger dynamics
and lower level 700mb jet around 40 kts, convective activity will be
capable of bringing down some stronger wind gusts. Precipitation
amounts Sunday through Sunday night will average 0.50" to 1" for
Pima, Santa Cruz and Cochise Counties with locales north of Tucson
including Pinal, Graham and Greenlee Counties along with favored
southwest flow upslope areas of our Sky Islands more likely to see
rain amounts ranging from 1 to 2+ inches. A Flash Flood Watch
remains in effect for 11 PM Saturday through 5 AM Monday for much of
southeast Arizona. This level of rainfall will result in flowing
washes, with subsequent increased flows in our river systems into
early next week as well.

Thereafter, we`ll get into a quieter weather regime early next week.
Any lingering precipitation should come to an end Monday morning with
shortwave ridging and dry conditions Tuesday and Wednesday. Thursday
still looks dry as well, then more uncertainty thereafter as another
system potentially impacts our area next Friday and beyond with more
precipitation chances.

Daytimes temperatures will mostly be below normal through the
forecast period, with the coolest highs Sunday and Monday.

&&

.AVIATION... Valid through 31/12Z. SCT-BKN clouds 7-10k ft AGL
through the forecast. Expect scattered to numerous SHRA and
scattered -TSRA through much of the period through 31/06Z, with the
most widespread precipitation this afternoon into evening. SFC winds
mainly SELY/SLY 6-12 kts through the forecast period, with gusts 15-
20 kts this afternoon. Gusty and erratic winds also possible near
any thunderstorm. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered to numerous showers and thunderstorms
today as weather system impacts the region. A brief break between
weather systems Saturday with only slight chances for showers, then
then widespread showers with scattered thunderstorms Sunday into
Monday. Moderate intensity rainfall with pockets of heavy rain is
expected today and Sunday, with locally heavy storm total rainfall
amounts possible, especially in the higher terrain. Afternoon high
temperatures will lower below normal through the forecast period.
Breezy southerly winds are anticipated Friday, with breezy to
locally windy southwest winds expected Sunday, turning northwest
Monday. Minimum RH values will be in the 15-25 percent range today
and Wednesday. Minimum RH levels will increase Friday into early
next week, with values at 40+ percent.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Saturday evening through late Sunday night
for AZZ502>511-513>515.

&&

$$


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