218
FXUS65 KPSR 111111
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
410 AM MST Sat Oct 11 2025

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

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

- Multiple rounds of showers with scattered thunderstorms will
affect much of the area with the heaviest rainfall and greatest
flood threat over higher terrain areas north and east of Phoenix.

- Showers and thunderstorm chances will persist across south-central
Arizona early next week before exiting the region.

- Temperatures will cool into a below normal range next week.

&&

.SHORT TERM /Today through Monday/...
Early morning WV imagery shows the remnant energy from TC Priscilla
crossing into northern Sonora with reinforcements in the form of TC
Raymond advancing towards the southern Baja. Meanwhile, pronounced
troughing remains situated along the Pacific NW coastline forcing
enhanced S/SW flow across the SW Conus. The pattern has allowed
copious amounts of deep tropical moisture to surge into the forecast
area with a massive plume of 12-15 g/kg mixing ratios and total
column PWATs above 2.00" covering the entire lower Colorado River
valley and surrounding area. Sheared vorticity being pulled into the
northern stream flow acting on this deep moisture pool has supported
a large shield of light/moderate rain over western AZ. However, a
significant limiting factor has been lack of instability as poor
lapse rates within the tropical environment has limited MUCape under
500 J/kg, and only a couple isolated thunderstorms have been
embedded in the moisture surge.

The Priscilla remnants will rapidly become unidentifiable later this
morning as the sheared vorticity and moisture plume shift into
eastern Arizona. While some enhanced areas of heavier rainfall are
likely, the limited instability should temper overall amounts around
the Phoenix metro and lower elevations with greater amounts favoring
the upslope foothill areas north and east of Phoenix. Rain rates
should not become unusually high with this round of rain, so slower
prolonged runoff leading to rises in smaller creeks, streams, and
washes is favored versus a rapid flash flooding risk. A period of
partial drying and subsidence should sweep into the CWA late
morning/early afternoon, however boundary layer mixing ratios 12-14
g/kg will linger across south-central Arizona setting the stage for
additional shower/thunderstorm chances late afternoon and beyond.

The aforementioned enhanced SW flow will begin scouring moisture in
the H7-H5 layer by early afternoon with downsloping in SE California
actually creating a quasi-dryline near the Colorado River. East of
the river, breaks in cloud cover will result in MLCape climbing near
1000 J/kg with minimal CinH. The largest uncertainty appear to hinge
on what forcing mechanism will encourage persistent deep updrafts and
maintenance of storms behind the exiting energy from Priscilla.
Perhaps enough synoptic vorticity will be present and/or merely
moist, uncapped flow over terrain escarpments will be sufficient.
Regardless, abnormally strong 0-6km deep layer shear (30-40 kt) will
be juxtaposed in this thermodynamic environment with any storm
development potentially obtaining 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
overnight 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.

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. Overall, NBM
POPs appear far too aggressive in both spatial and temporal extent,
and have attempted to refine this aspect of the forecast Monday
afternoon into Tuesday morning.

&&

.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 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 1110Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main weather weather issues though Sunday morning will be
periodic SHRA/TSRA resulting in brief periods of MVFR vsby and
potential for cigs flirting with 6K ft AGL. Numerous SHRA will
continue to stream across terminal locations through mid morning
with localized vsby 3-5SM in more moderate SHRA. An isolated TSRA is
possible, but odds are very low and should not be a significant
impact this morning. Confidence is moderate that SHRA will lift away
from the Phoenix area by late morning with an extended lull in
adverse weather through the evening as winds slowly shift from SE to
W/SW during the mid/late afternoon.

Forecast confidence is quite low this evening as overnight with
uncertainty in renewed SHRA/TSRA development. Storms could begin
developing as early as late afternoon around the airspace, but
equally likely could be delayed well into the overnight hours. Model
trends have been towards less SHRA/TS coverage during the
afternoon/evening, and more impacts during the overnight and Sunday
morning.


Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist through Sunday morning as
midlevel cigs above 10K ft AGL clear the area today. Winds at KIPL
will favor an E/SE component through mid afternoon before switching
to W/SW, and potentially becoming briefly gusty around sunset.
Variable winds at KBLH should favor a southerly component by early
afternoon with increasing gustiness before relaxing after sunset.

&&

.FIRE WEATHER...
Wetting rainfall will continue through Sunday over eastern districts
with drying in SE California. Conditions will steadily become drier
Monday and Tuesday. Rainfall may be prolonged in nature today, then
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. Erratic and locally gusty
winds will common around showers and thunderstorms the next several
days with more widespread gusty winds affecting the region Tuesday
afternoon/evening.

&&

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

CA...None

&&

$$

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