120
FXUS65 KPSR 052136
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
236 PM MST Mon Oct 5 2026

.KEY MESSAGES...

- Above normal temperatures with minimal day to day changes will
  exist through the start of the week as afternoon highs reach 97
  to 103 degrees across the lower deserts.

- An Extreme Heat Watch is in effect for portions of southeast
  California and southwest Arizona on Wednesday and Thursday as
  temperatures warm to near record levels and lead to Major heat
  risk.

- Dry weather with zero rain chances will persist through Saturday
  with shower and storm chances returning to AZ as early as
  Sunday.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...

It has been another breezy day across southern AZ, but winds have
not quite as strong as yesterday due to a weakening pressure
gradient. Surface pressure to the east is lowering which is
allowing the east-west gradient to relax. This weakening will
continue through tomorrow morning. So, there will still be some
breeziness in the morning tomorrow before the gradient fully
relaxes and winds return to a more typical light diurnal pattern.

High pressure remains in place over the Southwest, with midday
objective analysis showing H5 heights around 591dam, which is
just above the 90th percentile based on sounding climatology.
This high pressure, and mostly clear skies, will continue to
support above normal temperatures across the region. Latest
aircraft soundings out of Phoenix show little change in the low-
level thermal profile over the last 24 hours. So, high
temperatures this afternoon will be nearly identical to yesterday,
with lower deserts topping out around 97-103 degrees.

Heading through tomorrow and Wednesday a weak shortwave -
currently over northern NV - is expected to turn southeast and
drop through northeast AZ on Wednesday while a strong anticyclone
develops near the coast of SoCal. While the shortwave may lead to
isolated showers and storms up along the Mogollon Rim Wednesday,
the lower deserts are expected to remain dry. The shortwave will
also help keep south-central AZ from seeing a significant warm-up,
unlike areas to the west. Temperatures tomorrow will still be
similar to today, if not a degree warmer, and then temperatures
warm 2-4 degrees into Wednesday, with nearly all lower desert
locations reaching 100 degrees in the afternoon. Temperatures
will be hottest across southeast CA and along the Lower Colorado
River Valley, including Yuma, where highs on Wednesday will reach
the 104-107 degree range, which is upwards of 11-14 degrees above
normal for early October and will be near daily records. An
Extreme Heat Watch remains in effect starting Wednesday for the
Imperial Valley, CA and Yuma, AZ.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...

A strong anticyclone is expected to persist near the SoCal coast
through at least Thursday, which will keep temperatures well above
normal and near daily records across SoCal. Temperatures are also
expected to warm another 1-2 degrees across south-central AZ on
Thursday, following the passage of a weak shortwave trough. Even
south-central AZ will see high temperatures up to 10 degrees above
normal (99-102 degrees) on Thursday. An Extreme Heat Watch
remains in effect through Thursday for Imperial Valley, CA and
Yuma, AZ, where probabilities of Major HeatRisk are highest
(50-70%). This watch is likely to be upgraded to a warning tonight
or tomorrow morning and Friday is being considered for the heat
alert as well. Latest NBM forecast shows 30-50% Major HeatRisk
probs on Friday for the same areas under the current watch. The
coastal anticyclone is expected to breakdown heading into Friday
as the synoptic pattern shifts, with a Pacific low moving toward
the CA coast, but low level temperatures are expected to remain
very warm. Latest global ensembles show 850mb temps cooling by
only a degree or two centigrade into Friday, which should only
result in 1-4 degrees of surface cooling from Thursday. Latest
high temperature forecast for Friday has 101-106 degrees across
southeast CA and southwest AZ to 97-101 degrees across south-
central AZ.

As alluded to, the pattern will shift heading into the end of this
week and this weekend with a trend toward troffing and negative
height anomalies across the Western CONUS. While there is good
confidence in the trough pattern developing, there is still a lot
of model uncertainty/spread regarding how the trough pattern will
evolve heading into the end of the weekend and start of next week.
It does look like the Pacific low that will near the CA coast on
Friday will dip south this weekend and interact or faze with TC
Rachel while at the same time a trough will move out of the Gulf
of Alaska and strengthen as it moves south down the northern
Pacific coast. There are certainly a lot of eyes on what will
happen with TC Rachel and whether or not it will help bring rain
to the Desert Southwest, just like with TCs Odalys and Polo early
last week. Latest guidance has trended toward an eventual turn to
the northeast by Rachel by the end of the weekend. While this
trend does lend itself in favor of a push of moisture toward the
Southwest CONUS, there is still a lot of uncertainty in the
forecast this far out, especially with timing and evolution of the
trough moving down the northern Pacific coast and how that may
affect the remnants of Rachel. Current thinking is at least mid
and high level moisture will eventually shear off or Rachel up
toward the Southwest, which may bring showery activity as early
as Sunday and then the more potent coastal trough/low will help
drive additional shower and storm chances across AZ, while also
sending a cold front and cooler temperatures through the region
early next week. Again uncertainty is still high and it is ill-
advised to buy into single deterministic long-range model runs
that may show a strong tropical circulation pushing into the
U.S.. Stay tuned for forecast updates through the week.

&&

.AVIATION...Updated at 1700Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
NO major aviation concerns are expected during the TAF period.
Lingering breeziness will be on the downtrend and should become
more sporadic during the afternoon and evening. Easterly flow
will once again persist through the forecast window. Other than a
FEW mid-level cloud decks around 15 kft over the southern part of
the airspace, skies will be mostly clear.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected over the next 24 hours. Winds
will switch from a NE component this afternoon toward the NW by
this evening with periods of VRB conditions overnight. Mostly
clear skies will prevail across the region.

&&

.FIRE WEATHER...
Dry conditions with well above normal temperatures will continue
through the week, with afternoon high temperatures reaching up to
100-107 degrees across the lower deserts (hottest on Thursday).
Breezy easterly winds will continue across southern AZ through
this afternoon and Tuesday morning, with gusts up to 20-25 mph.
Winds will return to their more typical light diurnal tendencies
Tuesday afternoon through Thursday, with only minor afternoon
upslope gustiness. A gusty easterly gradient wind is expected to
develop again by Friday and last through Saturday. MinRHs will
mostly range from 15-25% across the western districts to 20-35%
across eastern districts through the week with fair to good
overnight recovery (35- 60%) area-wide. Humidities will be lowest
on Thursday when temperatures are likely at their hottest, but
winds will still be light at this time, so there are no elevated
fire weather concerns. No wetting rain expected through at least
Saturday. Rain chances then go up by the end of the weekend/start
of next week with increased moisture and a potential weather
system moving through.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Watch from Wednesday morning through Thursday
     evening for AZZ532.

CA...Extreme Heat Watch from Wednesday morning through Thursday
     evening for CAZ566-567.

&&

$$

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...RW
FIRE WEATHER...Benedict

NWS Phoenix (PSR) Office