743
FXUS65 KPSR 262321
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
421 PM MST Sun Jul 26 2026

.UPDATE...00Z Aviation Discussion.

&&

.KEY MESSAGES...

- Showers and weak storms continue to stream northward over
  Imperial County, California resulting in cloudy skies and much
  cooler temperatures than originally forecast this afternoon.

- Above normal temperatures will continue through the forecast
  period with Extreme heat Warnings in effect for portions of the
  area through mid week.

- Typical monsoon conditions are expected into next week with
  daily thunderstorm chances favoring Northern Arizona high
  terrain and Southeast Arizona and low chances in the South
  Central Arizona lower deserts.

- After a slight drop in temperatures during the first half of
  the coming work week, high pressure will strengthen over the
  region once again late in the week, resulting in another period
  of unseasonably hot temperatures and widespread Major Heat Risk.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...
A couple remnant weak vorticity centers which formed from
convective activity over northern Sonora yesterday evening have
passed into SoCal from the Gulf of California this morning,
forcing showers and several decaying storms ahead of them into the
western half of Imperial County into this afternoon. This has
resulted in considerable cloud cover and rain cooled air surging
through the Imperial Valley, leading to much cooler temperatures
than originally forecast. Clearing will occur on the backside of
these vorticity centers over the next few hours, resulting in a
quick warmup into the triple digits within the Imperial Valley,
but highs will likely struggle to reach 105F in the typically
hotter spots. Elsewhere across the forecast area, mostly clear
skies prevail, and intense surface heating under anticyclonic
subsidence will result in highs between 108F-113F for the lower
deserts.

Over the next few days, a low grade monsoonal pattern will
continue to evolve, with relatively weak easterly to southeasterly
flow maintained over the forecast area as a broad subtropical
high meanders over Colorado/NM. Near-surface mixing ratios will
hover between 9-11 g/kg, with dewpoints in the upper 50s to lower
60s across the lower deserts. Daily thunderstorm development over
the Northern/Central AZ high terrain and prominent terrain
features of Southeast AZ will continue to occur, with some
variation in coverage and intensity day to day, however, prospects
for lower desert storms across South-Central AZ are not great.
While moisture is marginally supportive of lower desert storms,
the threat is highly dependent on a forcing mechanism, such as a
strong, organized outflow boundary coming down from the Rim/high
terrain east of Phoenix or from Southeast AZ or mesoscale features
(e.g., MCVs from prior day convection). Additionally, forecast
soundings indicate MUCAPE values mostly staying below 1000 J/kg
and a modest cap with CIN staying mostly <-25 J/kg. Still, a few
storms may develop over terrain features of La Paz County and the
Table Top area in southern Maricopa County this afternoon and over
the next few days.

Dangerously hot temperatures with little overnight relief
continues to be the primary hazard as we head into the first half
of the coming work week. Ensembles remain in excellent agreement
that H5 heights will decrease from RAP analyzed 597-598 dam today
into a 594- 596 dam range by Tuesday as the subtropical high
weakens somewhat and remains centered solidly to our east.
However, the very warm air mass in place will not be dislodged,
and thermal profiles do not substantially cool as heights
decrease. NAEFS mean 850-700 mb temperatures between the 90th and
98th percentile of climatology will result in daily highs peaking
between 108F-114F across the typically hotter lower desert
locales, between 2F-8F above daily normals. The decent boundary
layer moisture remaining in place as well as debris clouds moving
downstream and over the forecast area from high terrain T-storm
activity each day will make for less effective radiative cooling
overnight, and so forecast lows are also elevated, remaining very
warm from the middle 80s to lower 90s. Temperatures drop a few
degrees heading into Tuesday/Wednesday, however, some of the
hottest lower desert locations remain in the Major HeatRisk
category, and so Extreme Heat Warning have been extended for the
Phoenix Metro, Yuma area, Lower CO River Valley, and Imperial
Valley through Wednesday. More expansive headlines will likely be
needed by late week as the subtropical high moves closer and
restrengthens.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
By the latter half of the week, most global ensembles support
notable strengthening of the high pressure, with 600dam H5 heights
materializing and the center of the anticyclone shifting to over
northern AZ/southern UT. The primary impact of this outcome will
be another extreme heat event with a return of widespread Major
HeatRisk and area of Extreme HeatRisk, beginning as early as
Thursday and the heat likely peaking on Friday and Saturday. There
is already high enough confidence to warrant extreme heat
headlines and the issuance of an Extreme Heat Warning, but it is
still being considered whether to just extend the current Extreme
Heat Warning through the brief reprieve Tuesday-Wednesday or
separate the events. This forecast outcome will also likely add
more subsidence over the area and subdue afternoon convection.
Global ensembles also show a slow downtrend in PWATs, falling
under 1.5" by Thursday-Friday. So, this is not great for the
prospects of seeing storms push into the lower deserts. Latest NBM
keeps slight PoPs focused in the AZ high terrain. The one
potential outcome that could increase chances for storms into the
lower deserts however is if the anticyclone can reposition closer
to southern NV, in a Maddox Type II position, to provide stronger
E-NE winds over the Rim.

&&

.AVIATION...Updated at 2320Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Aviation concerns will remain low through the forecast period. A
Gulf surge is expected to progress through the Phoenix Metro this
evening, mainly between 00Z-04Z, keeping winds elevated out of the
west with gusts up to 20 kts possible at KPHX and KDVT. Confidence
is now higher that there will be no outflow overnight with only
KIWA shifting out of the SE. Winds are then expected to return to
a more diurnal pattern late tomorrow morning with westerly winds
developing and some occasional gusts into the upper teens tomorrow
afternoon. FEW to SCT mid and high level clouds will prevail.

Southeast California/Southwest Arizona including KIPL and KBLH:
Aviation concerns will remain low through the forecast period. A
batch of showers over the Imperial Valley is finally dissipating
and allowing for winds to subside at KIPL. S-SE flow will return
later this evening into the overnight period. At KBLH, S-SW winds
are anticipated through tonight with speeds around 10-15kt. A Gulf
surge is then expected late tonight. This will keep winds southerly
with a few gusts reaching up to 20 kt at KBLH, mainly between
05-08Z. Current SCT-BKN mid lvl clouds will become FEW- SCT during
the overnight hours.

&&

.FIRE WEATHER...
Typical monsoon conditions are expected through much of the
forecast, with daily thunderstorm activity mainly favoring the
high terrain of northern AZ and southeastern AZ and low chances
(10%) in the lower deserts of south-central AZ. Above normal,
temperatures will contribute to seasonally dry afternoon
conditions each day through the first half of the week, before
temperatures once again heat up during the second half of the
week. Minimum RH values of 20-30% will be common through the first
half of the week before dropping into the 10-25% range late in
the week as temperatures heat up again. Overnight recoveries will
be fair most nights with RH values mostly in the 35-50% across
lower deserts to 45-65% across southern Gila County. Outside of
thunderstorm outflows, wind speeds should be fairly light through
the period with only local afternoon gusts 20-25 mph.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Wednesday for AZZ530-532-537-
     540-542>544-546-548-550-551.

     Extreme Heat Warning until 8 PM MST Monday for AZZ531-533>536-
     538-539-541-545-547-549-552>555-559.

CA...Extreme Heat Warning until 8 PM PDT Wednesday for CAZ567-569-570.

     Extreme Heat Warning until 8 PM PDT Monday for CAZ560>566-568.

&&

$$

SHORT TERM...Whittock
LONG TERM...Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict