882
FXUS65 KTWC 211621
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
921 AM MST Tue Jul 21 2026

.SYNOPSIS...
The combination of ample moisture across Southeast Arizona and
an upper-level disturbance moving across portions of the area
from the east will result in widespread showers and thunderstorms,
especially to the east and south of Tucson. These storms will
be capable of producing heavy rainfall. A Flash Flood Watch
remains in effect for Graham, Greenlee, Cochise and Santa Cruz
counties this through 10 PM MST this evening. Otherwise, daytime
temperatures will remain below average by several degrees into
midweek increasing to above normal late this week into this weekend.


.UPDATE 0915 AM...
Currently across SEAZ there is a fairly widespread area of
light to moderate rain showers moving from north to south in
central Pima County. Additional showers are moving from east to
west across the NM/AZ border. All of this activity is swirling
around a pronounced mid and upper level low. The low shows up
nicely in water vapor and will continue to meander N/NW through
the day. This feature will be the driving force behind another
active day.

Abundant moisture remains in place with areas in Graham,
Greenlee, Cochise, and Santa Cruz saturated. These areas will be
the main focus with the Flash Flood watch remaining in effect
through late evening.

Current thinking is a gradual development and expansion of
convection around the periphery of the upper low, especially
across Graham/Greenlee into Cochise County. With already
susceptible conditions, it will not take much to get flash
flooding. HREF once again paints a large area of 10% probs of
greater than 3" in much of the watch area. The entire watch has
a risk, but there is one area of more concern this afternoon
into the evening. That is Graham/Greenlee counties, possibly
extending into north/north-central cochise Co. As the low moves
toward the NW, that will increase confluent low level S/SE flow
in these areas, which could produce/enhance a south to north
training line of convection. There is more than one CAM showing
this solution, so its worth highlighting here. This could focus
a larger area of 3"+ on already saturated soils with
washes/rivers/creeks already showing responses.

As for the Tucson Metro, similar flavor as yesterday. High
likelihood of convection south and east of Tucson, including
the Santa Catalina/Rincon Mtns. The best chance for storms in
the metro will be the Catalina Foothills, Tanque Verde/east
side, and north into Catalina/Oracle. Anything that makes it
into the city center should be more of moderate to locally heavy
rain with embedded storms situation. Nonetheless, with abundant
moisture and above average soil moisture, we cannot rule out an
isolated instance of flash flooding.

&&

.DISCUSSION...
The combination of ample moisture and an upper-
level disturbance passing across portions of Southeast Arizona
from the east today will result in widespread showers and
thunderstorms...especially south and east of Tucson. These
storms will be capable of producing heavy rainfall, with
localized rainfall amounts between 1 and 3 inches. Given how
saturated soils are across the area from storms over the past
week, there is an increased potential that rainfall runoff to
produce flash flooding. A Flash Flood Watch remains in effect
for portions of Southeast Arizona (including Graham, Greenlee,
Cochise and Santa Cruz counties) through 10 PM MST this evening.

The upper pattern this morning continues to be defined by that
slow moving upper-low (seen by its distinct swirl in GOES WV
imagery) in west central New Mexico and an anomalously strong
ridge of high pressure centered over northwest Kansas. The upper
pattern remains in flux today as the upper-low moves over Graham
and Greenlee counties by 21/18Z today as the upper high center
moves SE into central Oklahoma. Given slower trajectory of the
upper-low, modest lift/deformation aloft will remain present
across the eastern CWA today when deep moisture remains. This
will result in another day of widespread showers and thunderstorms
with the potential for heavy rain to the east and south of
Tucson. This is supported once again by the 21/00Z HREF with a
10 percent probability of storms producing in excess of 3 inches
of rainfall in the Flash Flood Watch areas between 21/18 and
22/03Z. These areas got hit pretty hard with heavy rain
yesterday, which should increase the potential that any
additional heavy rain today will result in flash flooding.

Despite the fact that we will still have daily afternoon and
evening showers and thunderstorms the second half of the work
week, there will be a distinct downturn in activity. The upper-
high center will move from Oklahoma today to southern New Mexico
24/00Z Thursday afternoon then up to the Four Corner by 26/00Z
Saturday afternoon. The approaching upper-high will increase
afternoon temperatures once again to around 5 to 8 degrees above
normal. The combination of drier air and modest mid-level flow
will increase the potential for showers and thunderstorms next
weekend to be more of the severe variety. In other words, the
Monsoon rolls-on.

&&

.AVIATION /15Z TUESDAY THROUGH 15Z WEDNESDAY/...
Valid through 22/12Z. SCT-BKN 6-8k ft AGL BKN-OVC
8-12k ft AGL. After 21/19Z this afternoon through the late
evening hours...widespread showers and thunderstorms will
develop across Cochise, Santa Cruz, Graham and Greenlee
counties. These storms will be capable of producing heavy
rainfall. KOLS and KDUG are the terminals with the best chance
to see thunderstorms with brief MVFR possible under heavy +TSRA.
Sfc winds generally less than 12kts, except for around storms
where VRB gusts to 40kts will be possible. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...
Daily chances for thunderstorms will continue each afternoon
and evening through the next 7 days with day to day variability.
Widespread showers and thunderstorms are expected east and
south of Tucson again today. These storms will be capable of
producing heavy rainfall with the potential for flash flooding.
A Flash Flood Watch remains in effect until 10 PM MST this
evening for the eastern portions of Southeast Arizona. Min RHs
25-30% in the lower desert locations and above 40% in the
mountains through mid-week. By Thursday into the weekend, RH
could dip into the 17-22% range for the lower deserts west of
Tucson and the upper Gila River Valley as temperatures warm to
above average. Winds this week will remain mainly light and
under 15 mph, though strong and erratic winds will be possible
with any thunderstorm.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch through this evening for AZZ503-507>513.

&&

$$

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