789
FXUS65 KPSR 042317
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
417 PM MST Sat Oct 4 2025

.UPDATE...Updated 00z Aviation Discussion...

&&

.KEY MESSAGES...

- Dry conditions with clear skies and below normal temperatures
  will persist through the rest of this weekend.

- A gradual warming trend will commence next week, with afternoon
  lower desert high temperatures returning to the middle 90s
  midweek and upper 90s to 100 degrees late week.

- Increasing rain chances late next week into next weekend with
  at least a low chance for impactful flooding rainfall possible,
  but forecast confidence remains low at this time.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
Benign and fairly seasonal weather is expected the rest of this
weekend and the beginning of the coming work week. The shortwave
trough which has brought drier, cooler, and breezier conditions to
the region is seen on satellite lifting into Wyoming this
afternoon. A long-wave trough still remains in place across much
of the West. This long-wave trough, and the drier air brought in,
will help keep temperatures on the cooler side the next few days.
High temperatures this afternoon are forecast to reach the mid-80s
to 90 degrees across the lower deserts. Low temperatures this
morning were mostly in the 60s. Similar morning and afternoon
temperatures are expected again tomorrow. So, overall a very nice
weekend temperature-wise. However, continue to exercise caution in
the heart of the afternoons, as long exposure to the heat without
breaks or protection can lead to negative health impacts. Aside
from the below normal temperatures, breezy conditions will
continue this afternoon, primarily for southern Gila County, with
peak gusts up to 20-30 mph. Lighter winds are expected tomorrow.
Temperatures warm a few degrees Monday, as 500mb heights start to
rise, and winds will remain light.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
The highlight of the long term forecast continues to be the
potential for another high impact rain event with tropical
influences late next week. Newly named Tropical Storm Priscilla,
off the southern coast of Mexico, in the eastern Pacific, is
forecast to slowly drift northwest through the middle of the
coming week. Beyond this there is still a lot of uncertainty in
what will unfold for the Desert Southwest. The only couple of
certainties there seems to be at this time is that there will be
an increase in anomalous moisture into the Southwest U.S. and that
Priscilla will likely fall apart at sea as it moves closer to
higher shear around the base of the lingering trough pattern over
the northeastern Pacific and along the West Coast. There is still
the question of whether the remnants of the cyclone will turn
right, and be pulled northeastward by the trough, up into the
Southwest CONUS, stall and fizzle out, or turn westward further
out to sea. There are still several ECMWF ensemble members
favoring the remnants moving northeast into the Southwest,
including the deterministic, while the majority of GEFS and GEPS
turn the remnants west further out to sea. While there is good
confidence in anomalous moisture being pulled northward, the
remnants of the cyclone may be needed to provide a source of lift
in the region, as right now models are not showing too much in
the was of instability late week and into the weekend and the
better upper level jet forcing may stay further west and north,
favoring northern and western AZ and points north and west, at
least for the Friday time period.

It is still worth talking about this, despite being around a week
out and low confidence/low probability, due to the potential high
impact, especially after last week`s high impact flooding and
winds. There are model solutions with high rainfall amounts for
southern AZ and SoCal. The overall spread in model QPF is still
quite large, although there has been a slight backing off on the
number of solutions with extreme rainfall amounts. There are
still a few members members (10-15% of all members) with 1.5-2.5+
inches of storm total rainfall in parts of the region, including
Phoenix. There is also around 25% of members with no rainfall
accumulation. Many of the drier members involve 1) the tropical
remnants staying out at sea and 2) a stronger high pressure moving
in from the southeast. While a stronger ridging scenario doesn`t
look to decrease PWATs over our area it would push the the better
forcing (the coastal trough and remnants of the tropical system)
further west.

Timing-wise, the window for rainfall is still pretty large, and
there will likely be multiple days with rain, but best timing
still looks like Friday-Monday. However, some members still show
rainfall as early as Thursday, with the initial push of moisture
into the region. Ultimately, it is good to be aware of the
potential for another high impact rain event in 6-12 day forecast.

Prior to the rain chances for late next week the weather will remain
rather calm. Dry conditions with gradually warming temperatures are
expected for the first half of next week. With temperatures warming
back to near to slightly above normal across SE CA and SW AZ and
several degrees above normal across south-central and eastern AZ by
Wednesday. Morning low temperatures will also gradually warm, but
will remain near to slightly above seasonal levels. By the end of
next week and heading into next weekend, the temperature forecast
also becomes uncertain, just like the uncertainty in the
precipitation forecast. IQR spreads are currently around 6-12
degrees. Despite the uncertainty it does look like temperatures will
start to cool next weekend, the question is how cool will they go.

&&

.AVIATION...Updated at 2315Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns under clear skies are expected
throughout the TAF period. Winds will continue to exhibit the
typical diurnal tendencies with speeds remaining aob 10 kts. There
will likely be extended periods of light variability, especially
during diurnal transitions.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns under clear skies are expected
throughout the TAF period. Winds through tonight will favor a west
to northwest component with speeds remaining under 10 kts. Winds
will become more light and variable throughout the day Sunday.

&&

.FIRE WEATHER...
Dry conditions with no chances for rain are expected today through
at least Wednesday. Temperatures are below normal now, but will
warm during the upcoming week, back to normal to slightly above
normal as early as Monday or Tuesday. Breezy conditions this
afternoon will mostly focus across southern Gila County, with
westerly gusts up to 20-30 mph. Lighter winds are expected across
all districts tomorrow through early week. Daily minRHs of 12-20%
will continue through Wednesday, with overnight recoveries of
30-50%. There are increasing chances for wetting rainfall by the
end of next week, however, better chances exist for next weekend
and forecast confidence remains low. However, there is at least
high confidence that there will be an increase in moisture by the
end of next week pushing minRHs into the 20-30% range with
overnight recoveries of 45-65%.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Benedict
LONG TERM...Berislavich/Benedict
AVIATION...Lojero
FIRE WEATHER...Benedict