964
FXUS65 KPSR 241751
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1051 AM MST Sun Aug 24 2025

.UPDATE...Updated 18z Aviation Discussion.

&&

.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/...
The subtropical ridge remains in place across the Southwestern
U.S with the center just south of the Four Corners area. Drier air
has advected into the portions of our area, particularly into
eastern Arizona dropping PWATs down to below 1". Better moisture
remains positioned to the west across southern California and the
western half of Arizona, but PWATs there are still marginal at
between 1.2-1.4". Today should see a good deal of insolation
allowing temperatures to warm to around 110 degrees across the
lower deserts, but the amount moisture will still be a hindrance
for any widespread thunderstorm threat. The latest hi-res guidance
shows the best chance for showers and thunderstorms south and
west of Phoenix across western Pima, southern Maricopa, and
eastern portions of La Paz and Yuma Counties. High DCAPEs today
should promote strong winds and areas of blowing dust in the
aforementioned areas. As the event progresses, its possible there
may be some additional isolated convection into the Phoenix area
along any strong or colliding outflows. Another area of concern
for some isolated storms will be across Imperial County late this
afternoon/early evening as storms along the Baja spine may reach
or cause additional development into the Imperial Valley.

For tonight into Monday, our weather is likely to get even more
active as guidance shows a strong moisture fetch developing
across northern Mexico into our region. This will be aided by
increasing southerly flow along the outer fringes of an incoming
Pacific trough from the west and a subtle disturbance tracking
northward across Baja/Gulf of California. PWATs are forecast to
increase to between 1.5-1.7" for Monday across southeast
California through south-central Arizona with low level mixing
ratios increasing to a more favorable 10-12 g/kg. In addition to
the higher moisture, we are also expecting an increase in upper
level support and mid level southeasterly winds of 20-30 kts.
Despite the increase in moisture, guidance does not show any
increase in MUCAPE largely due to the expected increase in cloud
cover over much of the area. If any area could get good heating on
Monday, we could see some strong to severe storms given the
enhanced mid level winds. For now, we are assuming instability
will stay somewhat subdued given the expected cloud cover, but
that still shouldn`t stop convection from firing given the upper
level support. Hi-res guidance so far is pointing toward
southeast California and southwest Arizona having the best chance
for any stronger thunderstorms on Monday. This area should also
face a bigger threat of heavy rainfall and localized flooding with
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.

FEW to SCT mid and high clouds will be common through the TAF
period with lowest bases AOA 10K ft AGL.

&&

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