Cortaro, Arizona Weather Forecast Discussion

831
FXUS65 KTWC 262353
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
453 PM MST Fri Sep 26 2025
.SYNOPSIS...Isolated showers and thunderstorms with hazards of
damaging winds, hail, and heavy rainfall this evening. A Flash
Flood Watch in effect through Saturday evening and a Severe
Thunderstorm Watch is in effect until 7 PM this evening. Storm
chances linger this weekend then dry conditions expected next
week. Temperatures will be just below normal through Monday then
around normal thereafter.
&&
.UPDATE...Quick update to cancel the Graham and Cochise county
portions of the severe thunderstorm watch. Widespread cloud cover
has kept instability down through much of the watch area. Isolated
convection has developed in central Pima and Pinal counties,
however even further west instability has struggled to develop.
Increasing vorticity advection from the western trough will
continue thunderstorm chances through tonight, but the severe
threat looks to be waning. The Severe Thunderstorm Watch continues
for Pinal, Pima, and Santa Cruz counties until 7 PM MST.
&&
.PREV DISCUSSION... /issued 226 PM MST Fri Sep 26 2025/ Current
radar shows scattered showers and thunderstorms south of Tucson
with isolated storms in Pinal County. Most of the activity so far
has been to the north in Maricopa County. The closed low is at the
AZ/CA border with the best synoptic scale ascent currently over
Maricopa and Pinal Counties where the strongest storms are. Over
the next few hours it will slowly move eastward with better upper
level spreading over southeast Arizona. All the ingredients are in
place for strong to severe storms from central Pima County
eastward. The 26/18Z KTWC sounding measured SBCAPE of 1600 J/kg,
PWAT 1.27 inches, sfc-6km shear of 35 kts, dry mid-levels between
600mb-400mb, and a veering low level wind profile. This will
support storms capable of damaging winds and hail up to 1.5
inches. Because of this a Severe Thunderstorm Watch is in effect
for all counties except Greenlee. The latest WoFS run (20Z) is
highlighting better chances for severe hail with severe winds a
secondary threat. Over the next few hours it shows Pinal County
and central/eastern Pima County having the best chances for severe
hail. Expect thunderstorms activity in these areas to increase as
better upper level support moves over the area and surface
heating continues. Storms in Cochise County may struggle because
of cloud cover from shower activity. Heavy rainfall will also be a
threat with Santa Cruz County already under a Flash Flood
Warning. WoFS and the HREF are pinpointing Santa Cruz County,
Pinal County, and southwest Cochise County for the best threat for
heavy rainfall. Ensemble mean rainfall totals for those areas are
between 1"-2" with 90th percentile showing localized areas of 3
inches.
Saturday the low will still be along the AZ/CA border, but
moisture will be reduced likely leading to reduced coverage of
storms. This is backed up by hi-res guidance that shows isolated
to scattered showers and thunderstorms from Tucson eastward with
the best chances in Graham and Greenlee Counties. The heavy
rainfall threat is also reduced with HREF 3 hour 40 km
neighborhood probabilities for 1 inch of rain around 10 percent
for areas east of Tucson. Because of this will need to evaluate
the Flash Flood Watch in the future for Saturday. With storms
currently ongoing I will keep it in place for now. Sunday the low
begins to open up and moves through north central Arizona. This
will further reduce PWATS with thunderstorm chances mainly in
Graham and Greenlee Counties.
During the work week high pressure will build to the south
centered over northern Mexico with shortwaves passing well to the
north around the southern periphery of a large closed low in the
Pacific Northwest. This will lead to dry conditions next week with
temperatures right around normal through the middle of the week.
Later in the week ensembles are hinting at the ridge in Mexico
building further north which would raise temperatures to a few
degrees above normal.
&&
.AVIATION...Valid through 28/00Z.
SCT to BKN clouds 5-10k ft AGL mainly from KCGZ-KTUS-KOLS line E
today with SCT SHRA/TS through 27/04Z. Lclzd MVFR conds near
strongest storms. Gusty and erratic winds up to 40 kts and hail
possible near TS. Skies become SKC or FEW overnight then SCT-BKN
6k-10k ft AGL from Tucson east after 27/18Z. Isold TSRA possible
mainly east of Tucson during the afternoon. Outside of TSs, SFC
winds SLY to SWLY at 10-15 kts with gusts up to 25 kts and
overnight SELY 5-10 mph. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Expect scattered showers and thunderstorms today
from central Pima County eastward with some capable of damaging
winds and hail. Tomorrow and Sunday storm coverage decreases with
the best chances east of Tucson. General winds will be south to
southwest through next week with speeds up to 15 mph and gusts up
to 20 mph. The above normal moisture will keep min RHs above 25
percent through most of the weekend. Temperatures will be around
normal through the weekend. Next week, temperatures will be
slightly above normal with winds less than 15 mph and min RHs
18-22 percent in the valleys and 25-30 percent in the mountains.
&&
.HYDROLOGY...WPC QPF guidance today has 1" to 2" of rain across
much of the lower San Pedro River in eastern Pinal county and
Aravaipa Valley in western Graham county thanks to the potential
for training heavy showers and thunderstorms. Current WoFS runs
are also showing the potential for heavy rainfall in these areas.
We saw some river and creek responses yesterday and likely to see
more later this afternoon into this evening. My concern is
Aravaipa Creek and creeks and washes that drain into the San
Pedro. Something that we`ll need to keep and close eye on. Santa
Cruz County will also need to be watched with the Nogales Wash already
having a rise and a Flash Flood Warning in effect for Nogales.
Models continue to show more precip for Santa Cruz County which
will likely keep flow in the Nogales Wash elevated and flash
flooding a threat.
&&
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday evening for AZZ503>514.
&&
$$
Update...Edwards
Public...Hardin
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NWS TWC Office Area Forecast Discussion