754
FXUS65 KPSR 311954
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1254 PM MST Thu Jul 31 2025

.KEY MESSAGES...

- Hot temperatures with highs of 110+ degrees across the lower deserts
  will continue to persist through the next several days with at
  least widespread Moderate HeatRisk each day.

- Areas of Major HeatRisk are expected across portions of south-central
  AZ Friday and Saturday with Extreme Heat Warnings in effect.

- Another more widespread Extreme Heat Episode is likely mid to
  late next week, with near record high temperatures possible
  along with Major to locally Extreme HeatRisk.

- Overall dry conditions will prevail for much of the area with limited
  chances of showers and storms across south-central and eastern
  AZ today and Friday and possibly again early next week.

&&

.SHORT TERM /Today through Friday/...
Not much change to overall synoptic has materialized in the last 24
hours as an upper trough over the northern Great Basin continues to
impart dry southwesterly flow aloft, limiting any intrusion of
deeper moisture into the region. However, lower-level moisture
compared to the last couple of days has increased with the latest
model guidance showing PWATs rising between 1.1-1.3" this
afternoon through this evening. This increase in low-level
moisture may be enough to spark isolated storms late this
afternoon southwest of Phoenix, mainly across southwestern
Maricopa and western Pinal Counties near terrain escarpments with
the bulk of the storm activity, similar to the last couple of
days, confined to the eastern and southeastern third of AZ. Given
that substantial dry air remains in place across the mid to
upper-levels, it is going to be very difficult for any of these
storms that do develop across south-central AZ to last very long.
Nevertheless, with DCAPE values in excess of 1500 J/KG, cannot
rule out gusty winds and patchy blowing dust these storms. Heading
into Friday, as the westerly flow aloft remains in place, the
moisture will once again get scoured out throughout the day,
essentially ending any rain chances across the lower deserts with
some chances of afternoon activity across the eastern AZ high
terrain.

Aside from the limited rain chances, the main story heading into the
weekend will be the hot temperatures as the subtropical ridge
re-centers itself over the southern half of AZ and strengthens
slightly beginning on Friday. For this afternoon, high
temperatures will be similar to the last couple of days with highs
ranging between 108-111 degrees across the lower deserts.
However, as the ridge strengthens with 500 height fields
increasing to 596-598dm for Friday and Saturday, temperatures will
increase 2-4 degrees with lower desert highs for both days
forecast to range between 110-114 degrees. These high temperatures
in combination with above normal overnight low temperatures will
result in areas of Major HeatRisk developing across the lower
elevations of Maricopa and Pinal Counties and thus Extreme Heat
Warnings are in effect from Friday morning through early Saturday
Evening.

&&

.LONG TERM /Saturday through Thursday/...
The repositioning and the strengthening of the subtropical ridge
means any moisture will quickly get scoured out by Saturday
dropping rain chances to below 10% areawide. Surface dew points
are also shown dropping briefly into the 20s and 30s Saturday
before beginning to recover starting Sunday. The near zero rain
chances will continue to prevail into Sunday even as the ridge
begins to weaken again. Temperatures are forecast to drop a few
degrees going into Sunday, partially due to the weakening ridge
and also because of the more efficient overnight cooling from the
dry boundary layer conditions. Highs Sunday are still likely to
reach 110 degrees for many lower desert locations, but as of right
now nearly all of the area will fall below Major HeatRisk.

Guidance then shows the ridge shifting a bit farther to the east
over southern New Mexico early next week with H5 heights barely
budging across Arizona and southern California. This eastward
shift may allow for a return of some weak moisture, but it would
likely only be enough for some high terrain low end convection
for Monday and Tuesday.

Attention then turns toward a heavily favored scenario of another
Extreme Heat event by the middle of next week. Ensembles all agree
the ridge will restrengthen once again starting Tuesday, but while
also staying centered over New Mexico. The H5 center of the ridge
is currently forecast to strengthen to around 600dm by next
Wednesday or Thursday reaching record or near record heights for
the climatological period. H5 heights of 598-600dm will be
possible through much of our area by the middle of next week,
likely boosting our highs to between 112-116 degrees. The NBM is
already forecasting large areas of Major HeatRisk beginning next
Wednesday with guidance suggesting this next heat event would
last at least 2-3 days late next week. Some minor relief looks to
be possible by the following weekend.

&&

.AVIATION...Updated at 1154Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No significant aviation weather concerns are expected through the
TAF period. Winds will tend to follow light, diurnal tendencies
with a few afternoon gusts upwards of 15-20 kts. Isolated showers
and thunderstorms may develop across portions of southern Maricopa
County and northwest Pinal County this afternoon. If this occurs,
this could send an outflow towards the Phoenix area heading into
this evening. Any strong outflows that materialize will be
capable of generating areas of blowing dust. Confidence, however,
is currently too low to add mention of outflows into the TAFs at
this time. There are indications that isolated shower/storm
activity may develop near or over the metro after midnight
tonight. Any thunderstorms that were to develop would be capable
of producing gusty, erratic winds. Have not added any mention of
this into the TAFs at this time due to low confidence in this
solution.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under clear skies. Winds will initially favor the E-SE at
KIPL before transitioning to the W early this evening, with a few
evening gusts upwards of 20-25 kts. At KBLH, winds will
predominantly favor the S-SW with afternoon gusts upwards of 20-25
kts.

&&

.FIRE WEATHER...
The limited monsoon moisture will provide for another day of
mostly high terrain scattered showers and isolated thunderstorms
with diminishing chances already by Friday. Chances for wetting
rains will remain below 10% resulting in at least minor risk of
dry lightning. Afternoon MinRHs today and Friday will mostly be
between 10-15% across the lower deserts to 15-20% in higher
terrain areas before dropping further into the weekend. Outside
of the influence of thunderstorms, winds will generally follow
diurnal tendencies with typical afternoon upslope gustiness.
Temperatures will remain above normal with lower desert highs
mostly between 108-114 degrees. Dry conditions will prevail this
weekend with no rain chances before very limited mostly high
terrain chances return early next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Friday to 8 PM MST Saturday for
     AZZ534-537>544-546-548>555-559.

CA...None.
&&

$$

SHORT TERM...Lojero
LONG TERM...Kuhlman
AVIATION...Smith
FIRE WEATHER...Kuhlman