718
FXUS65 KPSR 062326
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
425 PM MST Tue Oct 6 2026

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- Above normal temperatures with minimal daily changes will carry
through the rest of this week as lower deserts top out around 97 to
108 degrees.

- An Extreme Heat Warning is in effect for portions of southeast
California and southwest Arizona from Wednesday through Friday as
temperatures warm to near record levels, resulting in major HeatRisk.

- Dry weather will persist through the at least the end of the
workweek before a potential cooler and more unsettled pattern
arrives this weekend into early next week.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
RAP analysis this afternoon shows a mostly quiet conditions across
much of the western CONUS, with only a very weak trough present over
the Intermountain West. Outside of this minor disturbance, high
pressure persists over the region and will continue to do so through
the middle portion of the week. 500mb heights currently stand around
588-591 dam, nothing too out of the ordinary for the Desert
Southwest, but still 1-1.5 standard deviations from typical
climatological normals during the front half of October. This
relatively enhanced atmospheric thickness will allow for
temperatures to warm further through the middle portion of the week,
pushing readings to around 10 degrees or so above normal for this
time of year, which translates to lower desert highs between 97-107
degrees. The higher end of the range will be collocated with the
highest heights, which will be focused over southwestern Arizona and
southeastern California. Although expected temperatures will be far
from what we see during the peak of summer, they will still reach
near record levels (see climate section), which will produce areas
of Major HeatRisk. As a result, the existing Extreme Heat Watch has
been upgraded to a Warning, which will go into effect starting late
Wednesday morning.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Though ridging aloft will begin to weaken during the back half of
the week, low-lvl thermal profiles will lag behind a bit as 850mb
continue to rise toward 26-27C into Thursday. This will result in
sfc highs reaching 102-108 degrees across the western deserts, again
nearing daily records in Yuma and the Imperial Valley. Major
HeatRisk is expected to be most expansive on Thursday afternoon,
leading to a spatial extension of the Extreme Heat Warning to
include the entire Lower Colorado River Valley and a portion of the
Gila River Valley in Yuma County including Dateland and Tacna.
Portions of south-central AZ will also see highs climb to around
100-103 or around 10 degrees above normal on Thursday, although the
HeatRisk is expected to remain in the Moderate category. Friday will
be a transition day where a deepening trough over the Pac NW which
in turn induces SW flow aloft over the West Coast. Although we will
begin to see a reduction in overall hghts aloft on Friday afternoon,
low-lvl thermal profiles will be slow to respond as 850 mb
temperatures are still expected to reach 25-26C across the much of
the forecast area equating to sfc highs around 100-105 degrees in
most lower desert communities. Due to these temperatures and
lingering Major HeatRisk for the Imperial Valley and Yuma area, the
Extreme Heat Warning will continue through Friday.

We then turn our attention to an upcoming pattern shift heading into
this weekend as most deterministic models and ensemble members are
trending toward an overall troffing pattern setting up across the
western CONUS. There is now better model agreement that a stronger
and deeper trough will transition into a cutoff low over the Pac NW
on Saturday and gradually sink southward into CA Sunday and Monday.
Meanwhile, latest forecast guidance from the NHC shows an eventual
turn to the northeast by Rachel this weekend with the remnants of
the storm itself being pulled northeastward and phasing with the
west coast trough. As this pattern transpires, there should be an
increase in southwesterly flow aloft over the Desert Southwest which
will begin to pull Pacific moisture into the region by late Saturday
into Sunday. Coincidentally, rain chances will return to the much of
the region with NBM PoPs now around 20-50% across south-central AZ
on Sunday and even up to 40-60% across the foothills NE of Phoenix
by Monday. There is still high uncertainty in rainfall amounts at
this time but there is at least a chance of some higher totals
exceeding 1.50" across AZ high terrain. As 500 mb hghts begin to
lower ahead of the approaching trough along with increasing cloud
cover and moisture, high temperatures will take a dive from the mid
90s on Saturday to the low to mid 80s by Monday.

&&

.AVIATION...Updated at 2325Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No weather issues will exist through Wednesday evening under
periodic midlevel cloud decks. Confidence is good that light west
winds will develop through mid/late evening before reverting to the
nocturnal easterly component. Behavior of winds Wednesday will be
nearly identical to today.


Southeast California/Southwest Arizona including KIPL and KBLH:
No weather issues will exist through Wednesday evening under mostly
clear skies. Extended periods of light and variable winds will be
common with a tendency towards a northerly component.

&&

.FIRE WEATHER...
Dry conditions with well above normal temperatures will continue
through the week, with afternoon highs reaching up to 100-107
degrees across the lower deserts (peaking Thursday). Winds will
return to their more typical light diurnal tendencies today and
persist into Thursday before increasing again Friday into this
weekend. 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. However, chances for wetting rainfall is expected to
arrive by the end of the weekend/start of next week as a weather
system begins to move into the region.

&&

.CLIMATE...

Record highs:

Date Yuma      El Centro
----     ----     ---------
Oct 7    111 in 2024105 in 1991
Oct 8 107 in 1996    106 in 1996
Oct 9 106 in 2024104 in 1996

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Wednesday to 8 PM MST Friday for
     AZZ532.

     Extreme Heat Warning from 10 AM to 8 PM MST Thursday for AZZ530-
     536.

CA...Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for
     CAZ566-567.

     Extreme Heat Warning from 10 AM to 8 PM PDT Thursday for CAZ569-
     570.

&&

$$

SHORT TERM...RW
LONG TERM...Salerno/RW
AVIATION...18
FIRE WEATHER...Benedict/Salerno
CLIMATE... RW

NWS Phoenix (PSR) Office