550
FXUS65 KPSR 040500
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1000 PM MST Fri Oct 3 2025

.UPDATE...Updated 06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Low pressure will brush the Desert Southwest today and bring a
  dry cold front through the region tomorrow morning leading to
  breezy to locally windy conditions and cooling temperatures
  heading into the weekend.

- A gradual warming trend will commence once again for the first
  half of next week.

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

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
A low pressure circulation currently centered just south of Lake
Tahoe, as seen on satellite, will push eastward over the next 24
hours and an associated dry cold front will drop down into
southeast CA and AZ tonight and Saturday morning. With the base of
the trough passing over the lower deserts and pressure packing,
breezy to windy conditions can be expected today and again
tomorrow primarily in eastern AZ. Today, widespread afternoon and
evening wind gusts up to 20-30 mph are expected, with strongest
gusts, up to 40-50 mph expected across parts of southeast CA,
especially in Imperial County with mountain downsloping
enhancements. The Wind Advisory in effect for western Imperial
County has been expanded to now include the Imperial Valley for
this evening through early-tonight. Latest HREF shows 50-70%
probabilities for wind gusts greater than 40 mph in the Valley.
These wind will be capable of generating localized dust channels
that may briefly reduce visibility under 5 miles.

After reaching the middle 90s to around 100 degrees across the
lower deserts today, temperatures will then cool by as much as 10
degrees by tomorrow afternoon, following the passage of the
trough to the north and the dry surface cold front. Lower desert
highs tomorrow are forecast to top out in the middle to upper 80s,
around 5-7 degrees below normal. Highs will then be a degree or
two warmer for Sunday. Dew point temperatures will also drop into
the 30s tomorrow afternoon. This drier air will persist through
the weekend and assist in some cooler mornings as well. Morning
lows in the 60s are expected this weekend for most areas. Being in
a desert, this may even feel a bit nippy for some people.

Isolated showers and storms are bubbling up in far eastern AZ
this afternoon, east of San Carlos, and will remain isolated in
this area and dissipate this evening. After this afternoon, with
drier air moving in, most of, if not all of, AZ and SoCal will be
cloud-free through this weekend.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The highlight of the long term forecast is the potential for
another high impact rain event with tropical influences late next
week. Current Invest 99E off the southern coast of Mexico, in the
eastern Pacific, is forecast to become a tropical storm within
the next 24 hours and then slowly drift northwest through the
middle of next week. Beyond this there is still a lot of
uncertainty in what will unfold. 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 the
tropical cyclone 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. One
question is whether the remnants of the cyclone will turn and be
pulled northeastward by the trough, stall and fizzle out, or turn
westward further out to sea. While there is good confidence in
anomalous moisture being pulled northward regardless, the remnants
of the cyclone may still 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 coastal
trough expected to remain coastal, which may limit dynamic
forcing.

It is still worth talking about this, despite being a week or more
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. Around 10-15% of global ensemble members
have 1.5-2.5+ inches by the end of next weekend. The extreme
members are driving up the ensemble means to the point where there
are periods where the means are higher than 75th percentile of the
full spread. The median (50th percentile) forecast rainfall
amounts from the global ensembles and NBM is actually no rain with
the latest runs. In addition to the large spread in rainfall
forecast amounts, there is a lot of uncertainty in when rain will
fall, or at least the best window for rain, but it is possible
that the best window of opportunity for rain may not come until
the coastal trough moves inland or a shortwave moves through the
base of the trough, which may not even happen until the beginning
of the following week. Ultimately, it is good to be aware of the
potential for another high impact rain event in 6-12 day forecast.

Before getting to this window of potential rain, the weather will
be pretty benign. Higher pressure is expected to nudge back into
the region from the southeast early next week that will result
high temperatures warming back to to a few degrees above normal by
the middle of the week, with lower desert highs in the middle 90s.
The morning lows will remain fairly cool and seasonal. Thursday
onward, the temperature forecast become more uncertain, due to the
uncertainty with the increasing rain chances.

&&

.AVIATION...Updated at 0500Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Lower than usual confidence on an easterly wind shift
overnight/early Saturday morning will be the only weather concern
under clear skies. Winds have relaxed but maintained a predominant
westerly component, which is anticipated to hold on for the next
several hours, strengthening at times but remaining AOB 10 kts.
While a shift to east winds is possible at KPHX between 12-17Z,
confidence is low and speeds would be light (AOB 5 kts), so opted
for prevailing VRB winds. Prevailing SW/W winds AOB 10 kts will
reestablish late Saturday morning and continue through the early
evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty west winds lingering late this evening will be the primary
aviation concern under clear skies. Speeds will be stronger at
KIPL, with gusts to 20-30 kts remaining for the next few hours.
Gusts have mostly subsided at KBLH, but cannot rule out occasional
gusts to around 20 kts for the next few hours. Wind directions
will tend to veer out of the northwest Saturday morning at both
terminals. Light NW winds generally AOB 8 kts will then prevail
for much of the day Saturday.

&&

.FIRE WEATHER...
Temperatures will start to cool out west today, but remain above
normal across the central and eastern districts, with some south-
central AZ lower desert locations seeing tripple digits again today.
Further cooling is expected this weekend region wide, thanks to a
dry cold front, with temperatures falling below normal. This cold
front will bring breezy to locally windy conditions to the region.
Gusts of 20-30 mph are expected across south-central and eastern
AZ this afternoon and evening. Gusts in excess of 40 mph are
possible across western Imperial County, otherwise gusts of 25-35
mph are expected across SE CA and SW AZ. The gusty winds will
continue through early Saturday morning across SE CA and SW AZ.
Gusty winds (20-25 mph) are expected Saturday afternoon and early
evening across the eastern AZ higher terrain. MinRHs will be in
the 15-25% range through the middle of next week, with overnight
recoveries in the 30-60% range. Gradually warming temperatures
and dry conditions are expected for the first half of next week.
There is increasing chances for wetting rainfall by the end of
next week, however, forecast confidence is low at this time. With
the increasing rain chances MinRHs currently look to increase to
30-40% for the end of next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 5 AM PDT Saturday for CAZ562.

     Wind Advisory until midnight PDT tonight for CAZ566-567.

&&

$$

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...Whittock
FIRE WEATHER...Berislavich