Severe Thunderstorm Warning 51, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
156 PM MST Sun Aug 24 2025

.SYNOPSIS...Shower and thunderstorm chances continue west of
Tucson today, then expand to the remainder of southeast Arizona
starting Monday. Expect daily chances for showers and
thunderstorms with day to day variability on coverage and intensity
through mid week with a drying trend later in the week. Above normal
temperatures through Monday then trending down to slightly below
normal Tuesday through Thursday. An Extreme Heat Warning in effect
until this evening for the greater Tucson area to southeastern Pinal
county.

&&

.DISCUSSION...Latest visible satellite imagery shows mostly clear to
partly cloudy skies east of Tucson and partly cloudy skies west of
Tucson. Scattered showers and thunderstorms have started forming in
the past hour or so across central and western Pima County and this
is the focus area for today as PWAT values range in the 1.25 inch to
1.5 inch range with MLCAPEs of 1000-1500 J/KG DCAPEs 1500-2000 J/KG.
Expect a few strong to potentially severe thunderstorms across the
western deserts this afternoon into early evening with strong winds
the main concern. Areas of locally heavy rain will also occur with
the strongest storms. Otherwise, the rest of the forecast area
should remain dry into the early evening. However, as additional
moisture filters in from the south and west, there is the potential
for some overnight into early morning showers and thunderstorms,
especially across western Pima County where the combination of
higher moisture levels and lift on the north side of an upper level
trough may aid nocturnal and early morning activity. The HRRR has
been consistent showing this scearnio for numerous runs now so it's
something we'll be watching through the evening.

Monday is shaping up to be an active day across our forecast area as
deeper moisture will continue to spread to the north and east and
the area will still be on the north (leading) side of an upper level
trough across Sonora. With PWATs increasing to 1.2 to 1.7 inches for
central and western portions of the forecast area (Pima, Pinal,
Santa Cruz Counties), this will result in MLCAPE values of 1000-1500
J/KG. The combination of the moisture and instability with lifting
from the trough will result in more widespread convection. The
highest confidence for storms is to the south and west of Tucson
with a bit lower confidence in Tucson/eastern Pima County and points
eastward. Note that locales close the NM border will remain mostly
dry with less moisture out that way. Storms should initiate
generally across Santa Cruz and south central Pima County then move
to the west and northwest with outflows helping kick off new storms.
Expect both severe wind and localized flash flood threats Monday.
Per coordination with SPC and WPC, WPC has placed portions our of
area in SLGT risk for Excessive Rainfall on Monday (and Tuesday)
with the SPC highlighting a MRGL risk for severe thunderstorms
(wind) from Tucson south and westward. Decided against hoisting any
flood watch headlines at this time as confidence on widespread flash
flooding still a bit low.

Tuesday will be highly dependent on what happens Monday. There will
still be well above normal moisture across our forecast area with
upper level troughing pushing through in the southerly flow aloft.
The focus on Tuesday might end up shifting to areas generally east
of Tucson which aren't expected to get as much on Monday.

Drier southwest flow aloft will start to move in on Wednesday and
this should help dimnish areal coverage of activity. Current PoPs
are in the 30 to 40 percent range but if the drying trends continue
we, we'll have to continue to lower them even more. This drying
trend should tend to hold Thursday through Saturday for most of the
forecast area (except possibly SE Cochise County) before additional
moisture tries to work back in later next weekend.

Temperatures will lower to seasonal normal levels Monday and then
drop to below normal Tuesday through Thursday before warming back up
to several degrees above normal next weekend.

&&

.AVIATION...Valid through 26/00Z.
SCT-BKN 9k-12k ft AGL. Widely scattered -SHRA/-TSRA west of KTUS
btwn thru 25/03z then isolated -SHRA/-TSRA thru 25/18Z. Aft 25/18Z
scattered-numerous SHRA/TSRA from KOLS/KTUS westward. Expect gusty
and erratic winds with any TSRA otrw SFC winds will generally be E-
SE less than 12 kts through 25/18Z. Thereafter, sfc winds mainly
WLY/NWLY with the exception of locales near the NM border. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Expect daily chances for rain showers and
thunderstorms through mid week with diminishing chances later in the
week into next weekend. Temperatures will be running above normal
again this afternoon with an Extreme Heat Warning in effect for the
lower elevations. Winds will generally remain less than 15 mph with
the afternoon gustiness this week. Min RHs will be 15-20 percent in
the low elevations and 20-30 percent in the mountains through the
weekend. Deep monsoon moisture early this week to provide higher
wetting rain chances and coverage as well as better min RHs and
below normal temperatures.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Extreme Heat Warning until 8 PM MST this evening for AZZ504>506.

&&

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson