486
FXUS65 KTWC 151010
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
310 AM MST Tue Sep 15 2026

.SYNOPSIS...An active week ahead with daily chances of showers
and thunderstorms with elevated risk of heavy rain and flash
flooding today through Thursday. Daily high temperatures will
fluctuate between near normal and a few degrees below normal.

&&

.DISCUSSION...Southerly flow will continue to persist across the
area through Thursday with well above normal precipitable water
values (PWATs) for September of 1.2" to 1.8" across southern
Arizona. This will keep elevated concerns for heavy rain from
thunderstorms, with hourly rainfall rates of 1"-2" (locally
higher), flash flooding and increased responses in already
saturated washes, rivers and creeks. WPC continues daily slight
risk for excessive rainfall across southeast Arizona with the
potential that Wednesday may be elevated up a category to
moderate risk.

Early morning water vapor imagery showed deep southerly flow
across northern Mexico into AZ/NM between upper low west of Baja
CA and the western flank of subtropical high over the southern
Plains. To the north there is the tail end of an upper level
trof that extends NE across the central plain into the Great
Lakes. Down to our south there is a developing upper low near
the southern tip of Baja that will be our weather maker
tomorrow.

Today: Morning regional radar (yes Tucson radar is down this
morning) showed isolated showers moving Gila county NE into the
Mogollon Rim and a few showers NE of Tucson. Additional weak
showers are possible through sunrise. The areal coverage of
storms this afternoon/evening will be less than yesterday due
to no discernible disturbance moving thru. However any storms
that do develop will be capable of producing hourly rainfall
rates of 1"-2" leading to localized flash flooding. Chances for
more scattered storms with locally heavy rain to continue into
the overnight hours are elevated versus previous days.

Wednesday: Convective activity will be more widespread than today
as models are all in pretty much in agreement on a strong upper
level disturbance/short wave, currently south of southern tip
of Baja, being ejected north out of Sonora MX across southern
Arizona. The dynamics associated with this feature will bring a
better chance of more widespread heavy rainfall with hourly
rainfall rates of 1"-2.5", with some areas possibly seeing over
3" of rain. This all leads to increased likelihood for flash
flooding with WPC having our area on the high end of slight risk
for excessive rainfall with the possibility that it could be
elevated to moderate risk later today. Flash flood watch will
likely be considered by us and our neighbors later today.

Thursday: PWATs remain elevated but there won`t be a disturbance
around like there will be on Wednesday, thus less areal coverage
of storms. However, still looking at scattered thunderstorms and
can`t rule out very localized heavy rainfall from any storms
that develop, especially east of Tucson, keeping the risk of
flash flooding elevated.

Friday through Monday: Drier air pushes into southeast Arizona
from the west as our flow aloft turns westerly. This will limit
any thunderstorm activity to areas east and south of Tucson with
significantly less chances for heavy rainfall.

8 to 14 day outlooks (Tue Sep 22 to Mon Sep 28)
Temperature: Leaning above normal, 37-39% chance
Precipitation: Leaning above normal, 40-44% chance

&&

.AVIATION...Valid thru 16/12Z.
SCT-BKN clouds 7k-10k ft AGL for much of valid pd with layers
clouds above. ISOLD -SHRA thru 15/16z, then SCT-NUM SHRA/TSRA
dvlpg aft 15/16Z. Outflow winds near TSRA of 35-45 kts. VSBYs
down to 1SM nr strongest TS. SFC winds terrain driven less than
10 kts thru 15/17z then again aft 16/05z. At other times, SFC
winds SWLY/SWLY at 6-12 kts. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...An active week ahead with daily chances of
showers and thunderstorms. High temperatures will fluctuate
between near normal and a few degrees below normal. Min RH
values mainly 20 to 45 percent in the valleys and 35 to 65
percent in the mountains over the next week. RH recoveries will
continue to be excellent overnight. Winds will generally remain
less than 15 mph and terrain driven. Gusty and erratic winds
will accompany thunderstorms.

&&

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

&&

$$

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