331
FXUS65 KPSR 250505
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Sun Aug 24 2025

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

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

- Temperatures cool into a near to below normal range through the
week resulting in only low to moderate HeatRisk.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
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 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
A fairly low confidence forecast exists starting Monday late
afternoon given large uncertainty with respect to thunderstorm
development, evolution, and outflow winds. In the meantime, winds
may never complete a true easterly switch late tonight potentially
just becoming variable around sunrise before quickly reverting back
to W/SW late Monday morning. A few stronger gusts near 20kt will be
possible during the mid/late afternoon.

The potential exists for significant operational impacts Monday
evening depending on proximity of thunderstorms and organization of
outflow boundaries. Modeling suggests TSRA with gusty outflows
developing over southern AZ, then surging north through the PHX
airspace early evening. Confidence is only low to moderate with
respect to timing and magnitude of gusts which could generate
localized BLDU. Multiple outflows are also possible which could
initiate renewed TSRA over aerodromes resulting in more direct
impacts, and have included a prob30 as models suggest limited
activity.


Southeast California/Southwest Arizona including KIPL and KBLH:
SHRA/TSRA with gusty winds will be the primary hazard to operations
through Monday night under periods of mid/high cigs above 8K ft AGL.
Confidence is fair that another round of TSRA similar to earlier
today will develop Monday afternoon south and west of KIPL. Gusty
winds with blowing dust and locally heavy rainfall are possible
before lifting away from the area in the evening. SHRA with some
embedded TSRA should approach KBLH Monday morning with good
confidence of prolonged, periodic SHRA into early Monday afternoon.
While S/SE winds will be common much of the time, wind directions
may be highly variable based on location and movement of
thunderstorms Monday afternoon/evening.

&&

.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...None.
CA...None.

&&

$$

SHORT TERM...Whittock
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman

NWS Phoenix Office