765
FXUS65 KPSR 302314
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
414 PM MST Sun Aug 30 2026

.UPDATE...Updated 00Z Aviation Discussion.

&&

.KEY MESSAGES...

- Active weather will persist through Monday with periods of
  showers and thunderstorms, some potentially producing strong
  winds and heavy rainfall across south-central Arizona.

- A Flood Watch is in effect for south-central Arizona this
  evening through the overnight period as heavy rainfall could
  result in localized amounts in excess of 1-2 inches and flash
  flooding.

- Quieter weather is expected by the middle of the week before
  potentially another more active period materializes by the end
  of the week into next weekend.

- Near to slightly below normal temperatures are expected throughout
  much of the upcoming week.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
Current objective analysis shows the subtropical ridge centered well
east of the area over the southern Plains while a broad trough
encompasses much of the western 1/3 of the CONUS. This pattern
configuration is resulting the flow to be out of the south-
southwest, aiding with maintaining elevated moisture levels across
the region as the latest SPC mesoanalysis shows PWATs of 1.5"+
across much of the AZ lower deserts and between 1.1-1.5" across the
higher terrain areas along with 10-12 g/kg of low-level mixing
ratios. The elevated moisture combined with 500 mb temperatures
cooling to between -7C to -8C will result MLCAPE values later this
afternoon into early this evening to peak at around 1500 J/KG. The
favorable thermodynamic environment combined with better ascent due
to increasing upper-level divergence from a jet streak moving
through the Great Basin will result in favorable conditions for the
development of widespread storm activity across much of south-
central AZ, especially from early this evening into the overnight
period.

Latest hi-res guidance, similar to yesterday, shows storms
developing across the AZ High Country as well as southeast AZ by the
early to mid afternoon hours. The activity across southeast AZ will
eventually send an outflow northward that will likely spark
additional storms into Pinal and Maricopa Counties with activity
affecting the Phoenix area heading this evening. Latest forecast
soundings for late this afternoon into early evening show a nearly
uncapped atmosphere once again and thus it will take just a
single outflow to result in convective initiation across the
lower deserts. Initially with the storms, strong downburst wind
gusts and areas of blowing dust in the dust prone areas will be
the primary hazards as DCAPE values will be high once again,
peaking at 1500 J/KG before heavy rainfall and flash flooding
eventually become the more primary hazard. Given the potential for
more heavy rainfall that could produce localized amounts of 1-2"
and thus lead to flash flooding, a Flood Watch is in effect for
much of south-central AZ starting early this evening and
continuing through the overnight period. There is a potential that
storms may last into the overnight period as some of the hi-res
guidance is showing given that an upper-level shortwave trough
will be approaching from the northwest that may aid in sustaining
the convective activity for a longer period of time with heavy
rainfall/flash flooding being the primary hazard.

The forecast for Monday remains a bit uncertain as everything
will be more conditional as to what happens later today into the
overnight period and how fast the atmosphere can recover. If the
atmosphere is able to recover fast enough where decent instability
develops, then another round of enhanced shower and thunderstorm
activity will be likely once again as the upper-level shortwave
will be positioned to the north-northwest over southern Nevada and
Utah, providing good upper-level ascent across much of central
AZ. Latest forecast soundings show very favorable thermodynamic
profiles once again with MLCAPE values exceeding 1000 J/KG along
with a uncapped atmosphere, supporting the potential for some
robust thunderstorms. However, this is assuming that the
atmosphere is able to fully recover from the activity that is
likely to materialize later today through the overnight period.

With the subtropical ridge now positioned well east of the area,
temperatures this afternoon will be noticeably cooler as readings
top out in the low to mid 100s across the south-central AZ lower
deserts and in the mid to upper 100s across the western deserts.
Even cooler temperatures are forecast for Monday, especially across
south-central AZ, where more abundant cloud cover and potential
rainfall may limit afternoon highs to just the middle to upper 90s
while warmer readings in the mid 100s are expected for the western
deserts.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A much quieter period of weather is anticipated starting Tuesday
as the flow turns more out of the west southwest ushering much
drier air through the rest of the area. Forecast PWATs are
expected to drop to just below normal on Tuesday, likely staying
on the lower side through around Thursday. NBM PoPs drop off to
mostly below 10% starting Tuesday and carrying through at least
Wednesday. Temperatures will also be a bit slow to warm back up as
the trough will still have some influence over our region.
Forecast highs return back into the normal range by Wednesday,
while overnight lows will be a more comfortable upper 70s to low
80s for the lower deserts.

High model uncertainty becomes an issue late week into next
weekend as models are currently favoring a tropical cyclone to
move northwestward off the coast of Baja and potentially even
getting close to California early during the following week. It is
impossible to know at this point where this TC will go, but it at
least seems fairly likely it will help to direct moisture
northward into our region by next weekend. Assuming this occurs,
we may eventually return to busy monsoon weather.

&&

.AVIATION...Updated at 2315Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Much uncertainty with the current TAF forecasts as another round
of thunderstorms, gusty outflow winds, and blowing dust expected
for later this evening. Delayed thunderstorm potential at TAF
sites by a few hours this forecast update. Thunderstorms over SE
AZ expected to become widespread early this evening and push a
strong S/SE outflow north into the valley TAF sites. Best timing
would suggest approximately 04z-09z with the initial outflow gusty
winds (>30 kts) as well as scattered thunderstorms developing
along this outflow and lowered visibilities in blowing dust. Even
after this initial wave of storms, there could be lingering
convection overnight which could impact overall wind trends as
well, straying from the typical diurnal trends. Please stay tuned
for future updates.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns are expected at the SE California
terminals. At KIPL, winds will fluctuate between westerly and
southeasterly. At KBLH, winds will fluctuate between southerly
and southwesterly through the TAF period. Speeds will be elevated
(10-15 kt) most of the period with some gusts of 20-25kt this
evneing. Skies will be mostly clear with FEW mid and high clouds
moving into the region this evening.

&&

.FIRE WEATHER...
Elevated moisture and rain chances will persist across the eastern
districts through Monday with gusty winds, heavy rainfall, and
localized flooding still a threat. The western districts will
generally stay dry with at most a few isolated showers and storms.
Expect MinRHs of 15-20% across the western districts to 25-40%
over the eastern districts before drying out again beginning
Tuesday. Temperatures will range from around normal over western
districts to slightly below normal over the eastern districts.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through late tonight for AZZ534-537-538-540>563.

CA...None.
&&

$$

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