415
FXUS65 KPSR 301909
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1209 PM MST Fri Oct 30 2026

- A Flood Watch remains in effect for portions of south-central
  and eastern Arizona through this evening.

- Shower and thunderstorm activity will persist for parts of the
  region, mainly from the Phoenix metro and eastward, through
  early tonight before eventually tapering off.

- A few strong to marginally severe thunderstorms are possible,
  with the main hazards being large hail and damaging winds.

- A followup weather system Saturday night into Sunday night will
  result in a period of prolonged light to moderate rainfall.
  Additional flooding concerns will exits, therefore, a Flood
  Watch will also be in effect during this timeframe for central
  and eastern Arizona.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
After morning warm air advection help to set off scattered
showers and thunderstorms across portions of the region, another
round of convective activity can be expected this afternoon and
evening, mainly from the Phoenix metro and eastward. SPC
mesoanalysis reveals a fairly tight corridor of MLCAPE 500-1500
J/kg stretching from western Pima County up toward Las Vegas. This
axis will be the focal point for the next instance of convective
initiation, and with a very supportive synoptic setup in place and
0-6km bulk shear profiles hovering near 30-40 kt, anything that
does form could be maintained for a decent period of time. With
this combination of instability and shear, some storms could
become strong to severe, potentially producing large hail and
strong winds.

Although PWATs are not as high as what we typically see during
Monsoon season, hovering around 1.0-1.3" according to
mesoanalysis, they still sit close to 250% of normal for this time
of year. Any stronger storms that can persist and continually tap
into this relatively moist environment will have the potential of
producing heavy rainfall that could lead to areas of flooding.
The flooding potential may be exacerbated by training convection
over the same areas and the fact that soil moistures remain
elevated from multiple rounds of rainfall over the past several
weeks. Ergo, a Flood Watch will remain in effect for portions of
central and eastern Arizona until this evening. When all is said
an done today, it is not out of the question that some areas could
see upwards of an inch to an inch and half, with locally higher
amounts.

The shortwave that is aiding in all this rainfall development
will eventually push off to the east by this evening/tonight,
resulting in a noticeable downtrend in activity for Saturday. Some
lingering, scattered showers may persist over upslope/higher
terrain areas of central AZ, as southwesterly flow remain elevated
on Saturday ahead of the broader troughing off the West Coast.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
By late Saturday evening, conditions begin to align for a longer
duration and more widespread rainfall event through Sunday. The
aforementioned subtropical jet streak is shown by global guidance
contracting and cyclonically curving around the base of the broader
troughing off the West Coast, as it begins to progress eastward.
Strong dynamical ascent mechanisms and a prolonged period of
southwesterly upslope flow over the Central AZ high terrain will
align with excellent, deep moisture through the atmospheric column.
Impressively high PWATs are still forecast, in excess of 1.00-1.25"
and near the maximum of climatology for early November. NAEFS/ENS
mean IVT values are consistent with an inland penetrating
atmospheric river and are also, unsurprisingly, near climatological
maximum values for the time of year (peaking around 300-600
kg/(ms)). However, midlevel lapse rates will be poor and thus
instability will be very limited, with MUCAPEs likely never
exceeding 200-300 J/kg. We expect showers to blossom first over the
high terrain northeast of Phoenix sometime in the evening Saturday
before filling in across most of south-central Arizona around or
just after midnight. Showers will stay somewhat scattered through
the overnight hours before becoming widespread over much of Arizona
by mid morning Sunday. As the main shortwave begins to track through
southern California later Sunday morning, a fairly solid shield of
light to moderate rain should move through southern California and
then through Arizona Sunday afternoon. Upslope showers should
persist over portions of south-central Arizona into the high terrain
into Sunday evening, but the activity should be gradually winding
down.

Expected rainfall rates on Sunday are not all that high, but rain
totals will add up over time as this event will last longer than our
typical weather events. Based on the record moisture levels, strong
forcing, but little instability rainfall rates will generally be in
the 0.1-0.2"/hr range in the Phoenix area to as high as 0.2-0.3"/hr
in the high terrain north and east of the Phoenix area. Fairly
steady light to moderate rainfall is expected from just before
sunrise through the afternoon in the aforementioned areas with
rainfall totals averaging 1-1.5" in Phoenix to 2-3" over the higher
terrain. Believe it our not, the NBM is also suggesting the
possibility (25%) of rainfall totals over 2" in the Phoenix to as
much as 3-4" in the high terrain. Much lower rainfall totals of 0.25-
0.5" are expected over the lower deserts of southwest Arizona and
southeast California due to some rain-shadowing effects and the lack
of upslope forcing.

Even if the average forecast rainfall totals come to fruition on
Sunday, the bulk of the rain will runoff as it will be falling on
already saturated soils. In turn, another Flood Watch has been
issued for a large area of south-central AZ, and the eastern AZ high
terrain starting overnight Saturday night and lasting into early
Monday morning. During this time we anticipate the potential for
many of the washes filling or overflowing, and flooding in some of
the larger creeks and rivers as all of the expected rain works
through the water basins.

Dry air will begin to filter into the region from the northwest
later on Sunday, overspreading the bulk of the area by Monday
morning. We may have some lingering showers across the eastern 1/3rd
of Arizona Sunday night into Monday morning, but additional rainfall
amounts should be fairly light. The rest of Monday will bring
decreasing clouds as the drier air works into the region while
another follow-on shortwave trough moves southeastward into northern
New Mexico. Temperatures for both Sunday and Monday will be fairly
cool with highs as low as the lower 70s for the Phoenix area to
maybe the mid to upper 70s across the western lower deserts. Upper
level ridging is then forecast to mostly take over across the Desert
Southwest going into the middle part of next week, but temperatures
will be fairly slow to rise with readings staying below normal.

&&

.AVIATION...Updated at 1755Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT;
Periods of MVFR CIGS and Vsbys in VCTS/TS will be the primary
aviation concerns through this afternoon before conditions improve
heading into tonight. The first round of showers and thunderstorms
is now moving NE of the terminals and we are expecting a lull in
activity for the next couple of hours. Another round of SHRA/TSRA
will develop around 19Z-20Z and likely impact the terminals for a
few hours with vsbys around 3-5 SM in heavy rainfall as well as
frequent lightning. Storm activity should diminish by sunset with
some lingering VCSH possible thereafter. SCT-BKN low clouds will
persist with bases around 4-5K ft AGL through much of the
afternoon before some clearing occurs this evening. Although the
extent of clearing is still uncertain at this time. E-SE winds
will prevail through most of the TAF period with speeds around 10
kts or lower. Some variability and a period of W-NW winds may
develop this afternoon as TS progress through the metro area.

Southeast California/Southwest Arizona including KIPL and KBLH:
No significant aviation weather impacts are expected through the
TAF period. SHRA/TSRA is forecast to remain well east of the
Colorado River Valley. At KIPL, westerly winds will prevail
throughout the period while at KBLH, winds will generally
fluctuate between the southeast to southwest. Overall speeds will
remain aob 10 kts with the exception of KIPL early this evening
as temporary peak gusts upwards of 20-25 kts are likely. SCT-BKN
mid to high level cloud decks along with FEW to occasionally SCT
decks around 5-6K ft will be common through this afternoon.

&&

.FIRE WEATHER...
Showers and thunderstorms will impact portions of the eastern
districts today with heavy rainfall likely in some areas, followed
by a lull in rain chances on Saturday. Minimum humidities will
range between 30-70% areawide today and Saturday and improve
further on Sunday, following excellent overnight recoveries. After
the lull on saturday, chances for rain increase again Saturday
night followed by widespread light to moderate rainfall on
Sunday areawide. Outside of any thunderstorms, winds will remain
generally between 10-20 mph and favor southeasterly to southerly
directions through the weekend. Conditions will gradually dry out
next week as the unsettled pattern departs and temperatures
moderate closer to seasonal normals, however, humidities will
remain above 25% areawide, and temperatures will still remain in a
slightly below normal category.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch until 10 PM MST this evening for AZZ552-556>558-
     560>563.

     Flood Watch from Saturday evening through late Sunday night for
     AZZ534-537>563.

     Flood Watch until 6 PM MST this evening for AZZ534-537>551-
     553>555-559.

CA...None.
&&

$$

SHORT TERM...Whittock/RW
LONG TERM...Whittock/Kuhlman
AVIATION...Benedict/Salerno
FIRE WEATHER...Whittock