541 
FXUS65 KPSR 091852
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1152 AM MST Thu Oct 9 2025

.UPDATE...Updated Aviation Discussion.

&&

.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:
An initial band of light SHRA is moving across the Phoenix area
now. Additional spotty SHRA is seen behind the band to the south.
VCSH is in the TAFs through 20-21Z when there may be a break.
Additional, rounds of VCSH/-SHRA is expected during the TAF
period, mainly tonight and heading into tomorrow afternoon. SCT to
BKN clouds will prevail through the entire TAF period, with VFR
CIGs and lowest cloud bases around 8-10K ft AGL. An E'rly wind now
will turn more N'rly to NE'rly this afternoon. Some erratic wind
shifts are possible with any shower. Potentially to a brief S'rly.
Wind speeds will mostly be in the 5-12 kt range through the
period, with an occasional gust up to 15-20 kt. The potential for
TS this period is very low and then increases tomorrow afternoon
and evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
Main aviation concern today is the potential for showers and
storms. Most of the activity through this afternoon looks to stay
outside of the vicinity of the terminals, with the highest
probability for convective activity being along the peninsular
mountains west of KIPL. VCSH mention in the TAF has been pushed
back to tonight. Multiple periods of showers are anticipated, with
another favored period beginning toward mid-morning tomorrow.
Winds a KIPL will shift to a W'rly to N'rly component this
afternoon, with extended periods of VRB, and KBLH will favor an
E'rly wind through this afternoon before shifting N'rly tonight.
FEW to BKN clouds decks, ~10kft, will persist. 

&&

.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 through Friday evening for AZZ530>533-535-536.

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

CA...Flood Watch through Friday evening for CAZ560>570.

&&

$$

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