Heat in Arizona, August 25 to 28, 2025

Area Forecast Discussion
National Weather Service Tucson AZ
848 AM MST Mon Aug 25 2025

.SYNOPSIS...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 today then trending down to slightly below
normal Tuesday through Thursday.

&&

.UPDATE...It's shaping up to be an active day across much of our
forecast area and those trends are on target. Latest visible
satellite imagery shows mostly clear to partly sunny skies across
our forecast area. PWATs are now in the 1.2 inch to 1.5 inch range
from Tucson westward, while drier air is hanging on east of Tucson
across Graham/Greenlee/Cochise Counties where PWATs are around 0.7
to 1.1 inches. Latest CAMs/HREF are in good agreement on convective
initiation between 18Z and 20Z, initially focused on Santa Cruz
County but quickly expanding to the north and west through the
afternoon. Convection today will be aided by divergence out ahead of
an upper level trough over Sonora. MLCAPE values of 1000-1500 J/KG
with DCAPE of around 1000-1300 J/KG. While individual storm motions
will be around 15 kts to the west and northwest, 20-25 kts of 0-6km
bulk shear will help support multi-cellular storms and development
of a larger cold pool capable of producing strong outflow winds. As
additional moisture continues to feed in today, flash flooding is a
threat as well, especially with merging cells/clusters. We already
have a Flash Flood Watch from Tucson westward and a Blowing Dust
Advisory for messaging both the flash flood and dust threats.
Meanwhile, for Graham/Greenlee/Cochise Counties, given the drier air
mass in those locales, thunderstorm activity will not be nearly as
widespread. Latest forecast is in good shape. No updates planned
this morning.

&&

.DISCUSSION...An approaching upper level trof from the southwest
will bring the needed lift to develop scattered showers and
thunderstorm and bring an active day across most of southeast
Arizona as the day progresses. The first round of scattered
showers/storms developed early this morning west of Tucson with a
couple cells rapidly developing near/SE of Ajo that resulted in a
couple of severe thunderstorm warnings being issued. Isolated
light showers/virga across the remainder of SE Arizona thru
sunrise. The main action will be occurring this afternoon/evening
as scattered storms develop across eastern Pima and Santa Cruz
county and they push west northwest into this evening. PWATs will
continue to increase as the day progresses with values up to
around 1.5" from Tucson-Nogales west. With the potential of
isolated severe thunderstorms and wet microbursts, a Blowing Dust
Advisory was hoisted along with a Flood Watch for mainly Tucson
west. There is the potential for some of the stronger cells this
afternoon to produce up to 2" of rain in less than an hour leading
to increased chances for flash flooding. WPC has portions our of
area in SLGT risk for Excessive Rainfall today (and Tuesday) with
the SPC highlighting a MRGL risk for severe thunderstorms (wind)
from Tucson southwest.

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
today.

Drier southwest flow aloft will start to move in on Wednesday and
this should help diminish areal coverage of activity. 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 this weekend.

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

&&

.AVIATION...Valid through 26/12Z.
SCT-BKN 9k-12k ft AGL. ISOLD -SHRA thru 25/18z. Aft 25/18Z
SCTD to NMRS SHRA/TSRA from KOLS/KTUS west. Expect gusty and
erratic winds with any TSRA otrw SFC winds will generally be
E-SE less than 12 kts. 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. 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...
 Flood Watch from 1 PM MST this afternoon through this evening
  for AZZ501>505-514-515.

 Blowing Dust Advisory from 1 PM to 4 PM MST this afternoon for
  AZZ502-504-505.

 Blowing Dust Advisory from 4 PM this afternoon to 7 PM MST this
  evening for AZZ501.

&&

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