159
FXUS65 KPSR 242207
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
247 PM MST Sun Aug 24 2025

.KEY MESSAGES...

- Moderate to Major Heat Risk and Extreme Heat Warnings remain in
  effect for much of the lower deserts today.

- A few strong storms will be possible today mainly between
  Phoenix and Yuma with strong winds and blowing dust the main
  threats.

- Widespread showers and storms are expected on Monday and
  possibly Tuesday with some storms being strong along with the
  potential for localized heavy rainfall and flooding.

- Temperatures cool to below normal starting Tuesday.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
For the rest of today, moisture looks to remain marginally
supportive of a few strong storms within the CWA, with isolated to
scattered development expected initially over prominent terrain
features between Phoenix and Yuma (better coverage over Western
Pima County, where several strong thunderstorms have already been
observed early this afternoon). RAP analyzed PWATS are generally
between 1.2-1.5" across Southwest AZ, though a layer of midlevel
dry air is still apparent in Yuma GFS bufr soundings for this
afternoon, which would act to inhibit convective potential. With
the subtropical high centered south of the Four Corners,
southeasterly steering flow will exist today of ~20 kts, acting to
push activity from Western Pima County into Southern Maricopa and
Eastern Yuma County, where DCAPE values are in excess of 1500
J/kg. This presents perhaps the best opportunity for strong to
marginally severe wind gusts today if storms survive into the
lower elevations, also presenting a concern for blowing dust.

A few large scale features evident in current midlevel wv imagery
and 500 mb RAP analysis will be key players in determining how
active our weather gets on Monday: an inverted trough in the Gulf
of California near the tip of Southern Sonora, and a larger upper
level trough with attendant jet max along its southern flank
approaching the CA Coast. Overnight, the inverted trough or
remnants of it are depicted by global guidance rotating
anticyclonically about the subtropical high and into the Western
CWA. Moisture will increase as this occurs, with ensemble mean
PWATS reaching 1.5-1.7". Most CAMs show showers with embedded
thunderstorms blossoming early Monday morning over Southwest AZ
with this moisture and elevated instability being imported over
the area. Simultaneously, the upper trough off the CA Coast draws
near, gradually cooling temperatures aloft (steepening lapse
rates). The jet max at its southern flank shows a pronounced
diffluent signature as it moves over the region, further
supporting the uncapped and favorable environment for storms to
form later in the day. One limiting factor for storm formation
will be lingering cloud cover over Southwest AZ into Southeast CA
from the aforementioned morning showers/storms, however, once they
clear the area, destabilization may be rather rapid, and areas
not clouded over stand a good chance of producing strong
thunderstorms. Localized flash flooding remains a concern for
Monday, particularly with thunderstorms that form in the mid to
late afternoon over SE CA and SW AZ; model soundings show midlevel
RHs in excess of 70%, and LCLs well below the freezing level, so
efficient warm rain processes and strong updrafts can produce
heavy rainfall - a few spots potentially seeing between 1-2" of
rain. Farther to the east across south-central and eastern
Arizona, instability and upper level support is likely to be less
supporting weaker storms but still fairly widespread coverage of
rainfall. PoPs on Monday remain quite high at 50-70% over the bulk
of the area.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Assuming Monday is quite active across the area with most areas
seeing showers and/or thunderstorms, Tuesday is likely to see
decreased chances of thunderstorms. Moisture is still likely to
be quite plentiful through much of Tuesday and colder air aloft
from the Pacific trough should spread eastward across the area.
However, the upper levels are likely to be less supportive with a
jet max nosing into southern California. The current forecast
thinking for Tuesday is the area of best rainfall potential is
likely to shift more over central and northern Arizona with
decreasing chances across California. Rainfall amounts on average
are likely to be on the lighter side, but we can`t rule out some
localized areas seeing upwards of an inch or so.

Starting Tuesday night, we should begin to see drier southwesterly
flow set up over our area, eventually pushing out any remaining
moisture by Friday. Forecast PWATs are shown to drop to between
1.2-1.4" by Wednesday afternoon and 1.0-1.2" by Thursday
afternoon. As a result, rain chances will quickly lower starting
Wednesday with PoPs falling to between 20-30% before dropping to
10% or less starting Thursday. This period of dry conditions
should last through at least next weekend.

Temperatures for the coming week will drop quickly early in the
week as moisture and cloud cover increases. By Tuesday, highs are
likely to drop to around 100 degrees across the lower deserts and
stay there again for Wednesday. As conditions dry out later this
week, highs are expected to slowly creep back toward normal
readings while overnight lows stay fairly comfortable in the 70s
for most places.

&&

.AVIATION...Updated at 1750Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds will follow diurnal tendencies through mid-afternoon with
speeds generally aob 10 kts. Shower and thunderstorm activity is
likely to develop later this afternoon, mainly to the west and
southwest of the Phoenix metro, with a westerly outflow making its
way through the terminals heading into early this evening. There
is a chance of a northerly outflow as well later during the
evening hours from the convective activity that develops to the
north, however, confidence of occurrence is low at this time.
There is a 50% chance of outflow winds exceeding 30 kts. Winds
should then weaken heading into the overnight period with light
and variable conditions expected before a westerly shift resumes
Monday morning. FEW to SCT mid and high clouds with decks aoa 10
kft AGL will be common throughout the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
A S/SE will be prevalent across the area terminals throughout most
of the TAF period, however, VCSH/VCTS will temporarily cause
erratic wind shifts. Best chances for VCTS late this afternoon
will be across KIPL, with activity likely to develop over
southwestern Imperial County, sending a westerly outflow with VCSH
most likely at KBLH. There is about a 50% chance of outflow winds
exceeding 30 kts. Outside of the thunderstorm outflow winds, the
overall wind speeds should remain aob 12 kts. FEW to SCT mid and
high clouds with decks aoa 10 kft AGL will be common throughout
the period.

&&

.FIRE WEATHER...
Above normal temperatures today will quickly cool Monday into
Tuesday as moisture and rain chances increase. Thunderstorm
chances are likely to be focused more across southwest Arizona
today before expanding into southeast California and south-central
Arizona on Monday with strong gusty winds being a concern.
Wetting rain chances will also increase to between 30-50% areawide
for Monday and Tuesday with localized heavy rainfall possible.
Afternoon MinRHs will continue to improve from around 20% today to
30% by Tuesday. Drying conditions are then expected later this
week with rain chances mostly coming to an end by Thursday.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530>555-
     559.

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ560>570.

&&

$$

SHORT TERM...Whittock
LONG TERM...Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman

NWS Phoenix Office