Gilbert, Arizona Weather Forecast Discussion

550
FXUS65 KPSR 041017
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
317 AM MST Sat Oct 4 2025
.KEY MESSAGES...
- A dry cold front moving through the region this morning will cause
temperatures to go below normal this 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 remains low at this time.
&&
.SHORT TERM /TODAY THROUGH SUNDAY/...
Upper level water vapor satellite imagery and objective analysis
show a closed low over the tri-state area of southern NV, NW AZ, and
SW UT. There is also a dry cold front extending southward from this
low through western AZ. This cold front is still causing elevated
winds (20-30 mph) across portions of SE CA and SW AZ. Additionally
there are still wind gusts of 40-50 mph in the far SW corner of
Imperial County. These winds will subside through the morning with
most most gusts ending around or shortly after sunrise. A Wind
Advisory remains in effect through 5 am PDT for the far SW corner
of Imperial County.
This cold front will quickly move through AZ this morning, exiting
into NM by this afternoon. This cold front will cause temperatures
to fall below normal today and tomorrow. Afternoon high temperatures
are forecasted to be in the mid to upper 80s to near 90 degrees
today across the lower deserts and in the low to mid 80s across the
higher terrain. This is a 8-12 degree cool down from yesterday`s
high temperatures across south-central AZ and a 6-9 degree cool down
across SE CA and SW AZ. Temperatures on Sunday will be very similar,
but may be a degree or two warmer. With the cold front bringing in
drier air and clear skies at night, morning lows will be able to
take advantage of radiational cooling with morning lows falling into
the 60s across the lower deserts and into the 50s across the higher
terrain.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
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 Ocean 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. Models this morning have backed off on the number of
solutions with the higher end rainfall amounts. However, there are
still a few EPS members with 1.5-2.5+ inches of rainfall. The GEFS
has backed off and now there are only two members with 1+ inches of
rain and the Canadian Ensemble remains the driest solution, with no
members having 1 of rain. The reasoning for the ensembles starting
to back off on the rainfall amounts for the end of next week and
heading into next weekend is because they now show a stronger high
pressure system, from the Gulf of America, trying to build back into
the Desert SW. While this 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.
There is also some slightly better agreement on when, or at least
when the best window, for rainfall will be. Ensembles have shifted
the window for best timing to be be later. So, now it looks like
next weekend and potentially even by the beginning of the following
week will be the best chance for showers and storms. The EPS is
favoring this solution, which it shows would be the result of a
shortwave moving through the base of the trough. However, some
members still show rainfall as early as the end of next week
(Thursday-Friday). 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 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...
A dry cold front moving through AZ early this morning will lead to
temperatures 6-12 degrees cooler than yesterday across the region.
The cooler temperatures continue tomorrow before a gradual warming
trend back to near to above normal temperatures by the middle of
next week. Breezy to locally windy conditions continues through
around or shortly after sunrise across the SE CA and SW AZ.
Wind gusts of 15-25 mph are possible in the higher terrain in
eastern AZ this afternoon and early evening. Otherwise, winds will
be light and follow their typical diurnal tendencies. Daily minRHs
of 12-25% will continue through Wednesday, with overnight
recoveries of 30-60%. 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, it
does look likely that we will get 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...Wind Advisory until 5 AM PDT early this morning for CAZ562.
&&
$$
SHORT TERM...Berislavich
LONG TERM...Berislavich/Benedict
AVIATION...Whittock
FIRE WEATHER...Berislavich

NWS PSR Office Area Forecast Discussion