810
FXUS65 KPSR 082340
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Fri Aug 8 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Hot conditions will continue to yield widespread Moderate to
  localized Major HeatRisk through early next week.

- The areas of Major HeatRisk through early next week will be
  concentrated particularly over the south-central AZ lower
  deserts, the Lower Colorado River Valley, and Imperial Valley
  and thus Extreme Heat Warnings are in effect through Tuesday
  evening.

- Chances for showers and thunderstorms will continue to remain
  quite limited into early next week, generally favoring the
  eastern Arizona high terrain.

&&

.SHORT TERM /Today through Sunday/...
The latest WV Satellite Imagery shows the subtropical high
centered over New Mexico with an anomalously deep trough over the
northern Rockies. With the 500 mb height fields lowering to
593-595dm compared to the almost 600dm that was in place the last
couple of days, afternoon high temperatures today will be about
3-5 degrees cooler compared to yesterday as lower desert highs
will range between 110-115 degrees. These temperatures will still
be hot enough to result in widespread Extreme Heat Conditions.
Temperatures over the weekend will be slightly cooler as the
subtropical high weakens very slightly with 500 mb height fields
closer to 592-594dm. This will translate to afternoon high
temperatures of 109-112 degrees across the south-central AZ lower
deserts and 109-114 degrees across the western deserts. These
slightly cooler temperatures over the weekend will be enough to
drop the HeatRisk levels into the high-end moderate category
across the majority of the area.

Areas of Major HeatRisk, however, will persist across the lower
deserts of south-central AZ as well as across the vicinity of the
Lower Colorado River Valley and the Imperial Valley. Gulf surges
through the weekend will maintain surface moisture levels
elevated, especially during the overnight and morning hours,
keeping overnight low temperatures elevated and thus offering
little overnight relief. This factor in combination with afternoon
highs near to slightly above 110 degrees will be the contributing
factors for the localized areas of Major HeatRisk to continue.
Thus, we have elected to extend the Extreme Heat Warnings for
the aforementioned areas through the weekend as well as through
early next week.

In terms of convective potential through the weekend, storm activity
will continue to remain relegated across the eastern and
southeastern third of AZ. Across the lower deserts of south-central
AZ, continued dry air in the lower-levels will result in strong
convective inhibition, limiting the potential for storm activity.
As a result, it will have to take a deep/colliding outflow
boundaries to overcome this convective inhibition, which at this
time seems unlikely to materialize given that the storm activity
over the higher terrain and southeast AZ is not expected to be
expansive enough.

&&

.LONG TERM /Monday through Friday/...
The continued passage of the trough to our north and northeast
early next week should continue to bring northerly dry flow into
much of our area Monday into Tuesday. Lingering moisture across
far eastern and southeast Arizona will continue to bring chances
for daytime convection, but only chances for outflow winds into
the south-central Arizona lower deserts. Guidance also shows the
subtropical high rebuilding across northern Mexico northwestward
through California and Nevada. H5 heights over our region will
generally stay fairly stable between 592-594dm, but with boundary
layer moisture dropping temperatures are forecast to increase by a
couple degrees starting Monday. NBM forecast highs for Monday and
Tuesday show readings between 108-113 degrees in Phoenix to
110-115 degrees across the western lower deserts. As a result of
these slight temperature increases, the Major HeatRisk coverage
has increased enough for the Extreme Heat Warnings to continue
across the south-central AZ lower deserts, Lower Colorado River
Valley, and Imperial Valley through Tuesday evening.

The latter half of next week is still looking interesting as both
the GEFS and EPS show the ridge shifting more over the Four
Corners area or northern New Mexico. Guidance also shows another
trough moving into the Pacific Northwest to as far south as
northern California and Nevada by around next Friday. So far
guidance shows the shift of the high to our northeast is likely
to bring more favorable southerly moist flow into Arizona as early
as next Wednesday or Thursday. Fortunately this time around the
subtropics is expected to be more active which would allow for
good quality moisture to be available to advect into our region.
The latest guidance shows anywhere from 1.3-1.7" PWATs into
southern Arizona by next Thursday or Friday. During this time,
NBM PoPs seem to be a bit too low, so we have increased PoPs
marginally for next Thursday into Friday. If this moisture does
actually move into our region, it should eventually lower our
temperatures closer to normal by next weekend.

&&

.AVIATION...Updated at 2340Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Occasionally gusty southwest to west winds will be the main
weather issue through Saturday afternoon under periods of FEW
mid/high cloud decks. Models continue to suggest a surge of gusty
SW winds ~25kt mid/late evening before slowly decoupling
overnight, and thus have maintained a TEMPO mention. The nocturnal
switch to easterly should occur later than usual Saturday
morning, followed by an earlier than usual switch back to W/NW
late Saturday morning (by 17-19Z).

Southeast California/Southwest Arizona including KIPL and KBLH:
Occasionally gusty winds will be the only weather issue through
Saturday afternoon under mostly clear skies and a few mid/high
cloud decks at times. Winds should maintain a south component at
KBLH and southeast at KIPL through the period, though some
variability is possible late night/early morning. Gusts 20-25kt
would be most common at KBLH.

&&

.FIRE WEATHER...
Very hot conditions with near record high temperatures will be
common again today with modest cooling, albeit still with above
normal temperatures arriving this weekend. A gradual moisture
increase today into Saturday may allow some isolated, weak storms to
develop from this afternoon through Sunday mainly focused over the
high terrain of far eastern districts. This should yield slight
chances (~10%) for dry lightning and new wildfire starts the next
couple days. Winds will follow typical diurnal patterns with
afternoon upslope gusts to 15-25 mph. Afternoon minRHs through
early next week will range between 10-20% with fair to good
overnight recoveries.

&&

.CLIMATE...

Record high temperatures this week:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Aug 8     116 in 2012    115 in 1940    115 in 2012

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Tuesday for AZZ534-537>544-
     546-548>551-553>555-559.

     Extreme Heat Warning from 8 PM this evening to 8 PM MST Tuesday
     for AZZ530-532.

     Extreme Heat Warning until 8 PM MST this evening for AZZ531-533-
     535-536-545-547-552-556>558-560>563.

CA...     Extreme Heat Warning from 8 PM this evening to 8 PM PDT Tuesday
     for CAZ562-563-566-567-569-570.

     Extreme Heat Warning until 8 PM PDT this evening for CAZ560-561-
     564-565-568.

&&

$$

SHORT TERM...Lojero
LONG TERM...Kuhlman/Lojero
AVIATION...Whittock/18
FIRE WEATHER...Kuhlman/Lojero
CLIMATE...18