026
FXUS65 KPSR 090944
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
244 AM MST Thu Oct 9 2025

.KEY MESSAGES...

- A Flood Watch has been issued for southeast CA and southwest AZ
  from this afternoon through Friday and all of south-central AZ
  from Friday through Saturday.

- Active weather with multiple rounds of showers and embedded
  thunderstorms will begin today and persist through at least the
  weekend. Some locations could receive rainfall totals exceeding
  2.00" which will promote excessive runoff into area watersheds,
  leading to flooding of low lying areas.

- Near normal temperatures today and Friday will cool to below
  normal starting this weekend. Expect highs across the lower
  deserts to lower into the 80s by Sunday and last week through
  the majority of next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Today will mark the first of several days of active weather
across the Desert Southwest, potentially lasting through next
Tuesday. Moisture and the eventual remnants of TC Priscilla will
affect the region today through Saturday followed by a second
tropical disturbance which is likely to send its moisture and
potential remnants across Sonora Mexico to as far north as
southeast Arizona at some point late Sunday through Tuesday. In
addition to the tropical systems, a strong Pacific upper level
trough hugging the Northwest U.S. coast will provide upper level
support throughout much of the period.

Strong moisture advection out of the south southeast into southern
Arizona and southeast California is currently ongoing. PWATs will
quickly rise from around 1.2-1.5" early this morning to 1.6-1.9"
by this afternoon from Phoenix through southeast California.
Scattered shower activity has already started to develop across
the area within the deep moisture advection and this should
continue through the rest of the morning. Fortunately, there is
very little instability at the moment with at most a few hundred
J/kg of MUCAPE. The strong moisture advection throughout the
entire column will lead to poor lapse rates for the bulk of the
area today with the only somewhat decent instability potentially
developing across southeast California by this afternoon. The
shower activity this morning is not expected to amount to much
rainfall, but once the instability grows across southeast
California this afternoon some thunderstorm activity will become
possible.

Hi-res CAMs have at times over the past 24 hours showed a cluster
of thunderstorms developing later this afternoon into the evening
across southeast California. The latest CAMs have backed off on
showing this potential, but we can`t rule it out. Due to the
excessive moisture that will be in place, any stronger showers or
thunderstorms that do manage to form will be capable of producing
moderate to heavy rainfall which may lead to localized flooding. A
majority of the CAMs also show bands of showers with some
potential embedded thunderstorms developing this evening and
through the overnight hours tonight anywhere from southeast
California and southwest Arizona to maybe northern Maricopa
County into Yavapai County. This activity is not likely to bring
heavy rainfall rates, but it very well could bring localized
0.25-0.50" per hour rates in some areas. Any training of cells
could easily bring localized rainfall amounts of an inch or more
in a few hours tonight into early Friday which may lead to some
localized flooding.

What will occur during the daytime hours Friday is still somewhat
uncertain, but guidance is leaning on the continuation of a band
of showers and the occasional embedded thunderstorm focused
either along the Lower CO River Valley or over southwest Arizona.
By the afternoon, we are likely to see more activity developing
farther east across south-central and eastern Arizona. Much of
this activity should be on the lighter side with moderate rainfall
rates at times, but it could easily bring decent rainfall over a
longer period of time.

The peak of the rainfall is then likely to occur during the
overnight hours Friday night through Saturday morning as the mid-
level remnants of TC Priscilla are expected to move across
Arizona from southwest to northeast. Enhanced forcing from the
remnants with strong mid-level southwesterly winds of 40-50 kts
should provide for fairly steady light rain with intermittent
moderate to heavy rainfall focused across south-central Arizona
Friday night and Saturday morning. WPC has added in a Moderate
Risk for excessive rainfall to account for this potential.
Eventually this activity should gradually shift more over eastern
Arizona by Saturday afternoon with periods of showers likely
lasting into the overnight hours Saturday night.

Forecast rainfall amounts have not changed much from previous
forecasts with amounts likely averaging 0.3-0.5" over southeast
California and 0.5-1.0" over southwest Arizona. Higher amounts
are expected over south-central and eastern Arizona where 1-1.25"
is likely across the lower deserts to 1.0-2.0" over higher
terrain areas. Localized higher amounts are expected to occur with
a few locations potentially pushing 2-3". Given much of this
rainfall is likely to be spread out over a couple of days, urban
flooding is not very likely. However, it will lead to flow within
area washes and small streams with some flooding likely to occur.

One other thing to mention is it may be possible to see a few
strong thunderstorms on Saturday as drier air is likely to push
into the area from the west leading to steepening lapse rates and
increased instability by the afternoon. There may be a brief
window potentially focused somewhere from Phoenix and just west of
Phoenix for strong convection to form if we see any decent breaks
in the clouds.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Considerable forecast uncertainty remains for Sunday through
Tuesday as a second tropical system may bring another period of
moderate to heavy rainfall to portions of Arizona. The best
potential is definitely expected to be over southeast Arizona, but
it very well could extend into our area. Guidance mostly agrees
the eventual remnants of this tropical system will traverse across
the Gulf of California on Sunday with another round of tropical
moisture shifting into at least southeast Arizona later Sunday
into Monday. The remnants of the TC are then likely to push
through Sonora Mexico providing ample forcing for rain across at
least southeast Arizona. The Pacific trough will also continue to
provide for good upper level support during this event as it is
likely one or more shortwaves will brush across northern portions
of the Desert Southwest.

Guidance shows moderate to heavy rainfall potential at least
extending into Gila County from as early as Sunday night through
as late as Tuesday afternoon with some members showing heavy
rainfall as far northwest as Phoenix. We will continue to monitor
for the potential for heavy rainfall through early next week and
can`t rule out the threat for some strong thunderstorms. The
tropical influence will likely push to the east of our region at
by later on Tuesday, but rain chances very well could persist
into Wednesday as models show a strong shortwave diving across at
least northern portions of our region later Tuesday into
Wednesday. However, by this point in time moisture availability
will be a concern as drier air is likely to be moving into the
region from the southwest.

Temperatures are forecast to drop going into the weekend with
readings eventually settling into the 80s for highs by Sunday. As
the Pacific trough begins to influence our region by early next
week, heights aloft will drop further and this will help to keep
temperatures below normal for several days. NBM forecast highs
show readings mostly in the low to mid 80s for the at least the
first half of next week and potentially even through all of next
week.

&&

.AVIATION...Updated at 0555Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Tonight VCSH will be common at all terminals with E`rly winds
expected well into the morning. By tomorrow morning (~17Z) -SHRA
is expected at KPHX and KIWA, which can reduce visibilities to
5SM, in addition to wind speeds increasing between 10-15kts with
gusts upwards of 20kts possible. These elevated wind speeds will
linger throughout the afternoon but look to relax to aob 10kts by
near midnight tomorrow. No W`rly shift is expected tomorrow
afternoon as directions will remain out of the E to NE. FEW-BKN
clouds decks, ~10kft, will persist with this incoming activity.

Southeast California/Southwest Arizona including KIPL and KBLH:
Main aviation concern is shower activity throughout a majority of
the TAF period at both terminals. VCSH will be common through
tonight with a brief break tomorrow morning before -SHRA returns
for most of the remaining hours. Winds a KIPL will be SE`rly with
extended periods of VRB and KBLH will shift out of the NE tomorrow
morning and throughout the afternoon. FEW- BKN clouds decks, ~10kft,
will persist with this incoming activity.

&&

.FIRE WEATHER...
A significant influx of moisture will progress westward through
region today, allowing for increasing coverage of showers and
isolated thunderstorms. The main focus for wetting rainfall will
be over western half of the forecast area today before spreading
into southcentral Arizona Friday and Saturday. Easterly winds
will persist across the eastern districts through Friday with some
gusts upwards of 25 mph at times. Winds across the western
districts should tend to favor the east today and then out of the
north northeast tonight into Friday. Due to the increase in
moisture and rain chances, temperatures will gradually cool from
near normal to below normal by this weekend.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch from noon MST today through Friday evening for
     AZZ530>533-535-536.

     Flood Watch from Friday afternoon through Saturday evening for
     AZZ534-537>563.

CA...Flood Watch from noon PDT today through Friday evening for
     CAZ560>570.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Ryan
FIRE WEATHER...Kuhlman

NWS Phoenix Office