649
FXUS65 KPSR 120018
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
518 PM MST Sat Oct 11 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- A Flood Watch remains in effect for south-central Arizona
  through Sunday night.

- Periods of isolated to scattered showers thunderstorms are
  forecast for late this afternoon through Sunday in south-central
  Arizona area with the heaviest rainfall and greatest flood
  threat over higher terrain areas north and east of Phoenix.

- Shower and thunderstorm chances will persist across south-
  central Arizona Monday before exiting the region.

- Below normal temperatures are expected throughout the next
  week.


&&

.SHORT TERM /Today through Monday/...
A persistent band of light to moderate rainfall progressed from the
western deserts through the central portions of AZ last night
through this morning, leading to widespread rainfall accumulations
from 0.25" to as high as 1.50" across the lower deserts. Highest
amounts were mostly in Maricopa County. The 0.70" at Phoenix Sky
Harbor, through 11 AM, easily broke the daily rainfall record of
0.31" from 1928. Sky Harbor`s 3-day total is now up to 1.06".
Despite the higher rainfall totals seen with the band this morning,
there has not been any significant impacts, besides wet roads,
puddling of water and some running washes. The USGS gauge on Tonto
Creek north of Tonto Basin has seen a rise, but so far has stayed
below action stage. There has been bigger flooding impacts further
north between Flagstaff and Payson, where upwards of 4.0-4.5" of
rain has fallen. A lot of this water is entering the Verde and Agua
Fria river systems, which head down to Horseshoe Lake and Lake
Pleasant, respectively.

For the rest of today, the band of showers, associated with the
remnants of TC Priscilla, will continue to lift away from the area
and drier air will continue to move in aloft, as seen on wv
satellite. This drier air aloft will scour out the mid and high
clouds and allow for more sunshine through this afternoon. The
boundary layer will be much slower to dry out across south-central
AZ, with mixing ratios forecast to remain around 12-14 g/kg through
tonight and likely through Sunday as well. Meanwhile, areas further
west, from near the lower Colorado River and points west, will be
hit with a dry cold front this evening and tonight that will scour
out the boundary layer moisture, with mixing ratios forecast to drop
under 7-8 g/kg. So, for south-central AZ this afternoon, the
question is whether the environment can recover from this
morning`s rain and see enough surface heating to overcome some
subsidence in the wake of Priscilla to generate some convection.
As of early this afternoon, it does not look promising.
Temperatures through south- central AZ were still in the middle to
upper 70s as of 1 PM MST. Highs this afternoon are not likely to
get to the original NBM forecast of around 90 degrees for the
Phoenix area. These cooler temperatures will hurt the convection
chances this afternoon. There are hi-res models with support for
perhaps some isolated development in the Tabletop area south of
I-8 and around Wickenburg. The experimental hi-res ensemble Warn-
on- ForecastSystem also has little to nothing for the lower
deserts.

Should isolated convection get going this afternoon, abnormally
strong 0-6km deep layer shear (30-40 kt) will be juxtaposed with
MLCAPE values around 500-1000 J/kg, so storm development may obtain
organized structure with locally strong winds, small hail, and heavy
rainfall. PWATs still hovering near 1.50" and the improved
instability should result in a more conducive environment to support
heavy rain.

HREF and most global scale modeling suites suggest many favorable
ingredients for heavy rainfall coming together this evening though
Sunday across parts of south-central Arizona. Increasing ascent from
the combined influences of TC Raymond approaching from the south and
height falls/right jet entrance region encroaching from the NW may
align somewhere in south-central Arizona. Prolonged ascent and
nearly unidirectional flow within the cloud bearing layer may create
an environment of elevated, training echoes into the overnight with
MUCape near 1000 J/kg potentially tapping PWATs continuing to hover
around 1.50". The preponderance of model evidence suggests activity
shifting into SE Arizona Sunday afternoon following the migration of
more robust height falls and theta-e axis associated with the
Raymond moisture surge. This is when flash flooding becomes a
greater risk. With storms capable of producing higher rain rates, up
around 1"/hr, in areas with already saturated soils, most of the
rainfall is likely to go right into runoff. Latest HREF has high
probabilities (80-90%) for 3 hr rainfall >0.5" east of Phoenix early
Sunday morning and 10-20% chances for >1" in 6 hrs.

Lingering shallow moisture (mixing ratios 10-12 g/kg), renewed
height falls with additional incoming East Pacific energy, and a low
level upslope component will aid in continued POPs Monday -
particularly in higher terrain locations north and east of Phoenix.
By this time, instability should become more limited while total
column moisture is eroded closer to 1.00" resulting in lower
probabilities of heavy rains. However, deep layer shear remains
quite impressive (0-6 km over 40kt), and capable of supporting
better organizational structure for any storm that can develop, and
thus not impossible for isolated flooding rainfall.

&&

.LONG TERM /Tuesday through Friday/...
Deep negative height anomalies diving south along the central
California coast will lift into the Great Basin during the middle of
the week bringing pronounced, dry westerly flow into the forecast
area. Boundary layer moisture will rapidly be scoured Tuesday with
downsloping and rainshadowing effects downstream of the coastal
mountains. This pattern will yield some gusty winds Monday and
Tuesday afternoon and evening, primarily in the most wind prone
locations of SE California, but also ensuring a cool, dry forecast
the remainder of the week.

Ensemble membership is in fairly good agreement depicting broad
troughing somewhere in the northern Rockies/Great Basin/central high
plains throughout the latter half of the week with marginally lower
heights aloft and weak, positively tilted troughing maintained
across the SW Conus. This pattern favors a mostly dry outcome with
temperatures 4F-8F below normal as H5 heights hover in a 572-578dm
range.

&&

.AVIATION...Updated at 0018Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The primary aviation weather concern through the TAF period will
be continued chances of showers and thunderstorms. Radar late this
afternoon showed quiet conditions across the Phoenix area with low
confidence of shower/thunderstorm development through this
evening. Thus, have opted to remove any mention from the TAFs
through this evening for now. There is better confidence, though
still uncertain, that showers/thunderstorms will develop tonight
into the overnight hours and persist into Sunday morning. Any
heavy showers and thunderstorms that develop during this time may
result in brief MVFR visibilities due to heavy rain. By mid/late
morning Sunday, hi-res guidance have any activity trending down
with linger VCSH through the afternoon. FEW-SCT clouds aoa 5-7 kft
are expected to become SCT-BKN going into the overnight hours
before decreasing in coverage going into Sunday afternoon. Outside
of any erratic winds with the aforementioned activity, winds will
favor the east throughout the period with periods of light and
variable winds.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns under some lingering low to
mid-level clouds decks can be expected. Winds at KIPL will briefly
favor a southeasterly component before switching out of the west
this evening. At KBLH, winds will generally fluctuate out of the
south to southwest through tonight before switching to the north
to northwest overnight. Sustained speeds will remain aob 12 kts,
however, some gustiness near 20 kts can be expected this evening
at KIPL.

&&

.FIRE WEATHER...
Elevated wetting rain chances will continue through Monday over
eastern districts with drying in SE California and SW Arizona
today. Conditions will steadily become drier heading into
Tuesday. Rainfall may be heavy at times Sunday and Monday
resulting in localized flooding, especially over higher terrain
areas. Elevated moisture levels will keep humidity levels in
eastern districts above 50% through Monday, then minimum values
falling into a 20-30% range during the middle and end of next
week. Western districts will generally experience afternoon
humidity values in the teens to lower 20s. Erratic and locally
gusty winds will common around showers and thunderstorms the next
several days with more widespread gusty winds affecting the region
Monday and Tuesday afternoon/evening.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through Sunday evening for AZZ534-537>563.

CA...None.
&&

$$

SHORT TERM...Benedict/18
LONG TERM...18
AVIATION...Smith
FIRE WEATHER...18