471
FXUS65 KPSR 061911
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1211 PM MST Tue Oct 6 2026

.KEY MESSAGES...

- Above normal temperatures with minimal day-to-day 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 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns under FEW occasional mid-level cloud
decks can be expected throughout the TAF period. Winds today will
return to a more traditional diurnal pattern with the westerly
shift likely by mid-late afternoon. Wind speeds are expected to
remain light, mostly below 10 kts.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns will exist through the next 24 hours
under mostly clear skies. Winds will generally remain light, with
extended periods of variability and directions favoring a westerly
component at times.

&&

.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...Whittock/Lojero
FIRE WEATHER...Benedict/Salerno
Climate... RW

NWS PSR Office Area Forecast Discussion