344
FXUS65 KPSR 212330
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
430 PM MST Fri Aug 21 2026

.UPDATE...00Z Aviation Discussion

&&

.KEY MESSAGES...

- High temperatures reach or exceed 110 degrees nearly every day
  through the next week and will be within a few degrees of daily
  records, while morning lows remain unusually warm.

- Extreme Heat Warning in effect through next Friday evening with
  daily Major to Extreme HeatRisk.

- Isolated thunderstorms will primarily favor higher terrain areas
  through this weekend, with drier and less favorable conditions
  next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Extreme heat will be the primary weather hazard through the
short, and long, term forecast. Latest objective analysis shows a
599dam high centered near the Four Corners region, with 596-598dam
heights over the local area. Heights of this magnitude are at or
above the 99th percentile of sounding climatology. So, it is no
surprise that forecast high temperatures this afternoon, and
through this weekend, will be within a few degrees of daily
records, topping out around 110-116 degrees. Morning low
temperatures will also remain very warm and near daily record warm
lows, in the mid 80s to low 90s, offering little to no relief
from the daytime heat. This combo will lead to widespread Major
HeatRisk through the weekend and an Extreme Heat Warning remains
in effect.

The thunderstorm chances for the lower deserts this afternoon are
not great, due to the warm air aloft and drier air that moved in
aloft as well. However, surface dew point temperatures remain
seasonally elevated, ranging from the mid-50s to mid-60s. This is
contributing to high SBCAPE values early this afternoon, up to and
in excess of 1500 J/kg. This setup was resulting in cu development
over prominent terrain features as of 1 PM MST and strong storms
were already going over southeast AZ where mesoanalysis was
showing an uncapped environment. The cap over much of south-
central AZ and points westward, although relatively weak (SBCIN
between -20 to -40 J/kg) will likely keep convective development
reserved to the prominent terrain features, like the Table Top
Mtns, Kofas, and perhaps Pinal Mtns. Instability is also expected
to decline through the rest of the afternoon as the PBL continues
to mix out. This will inhibit updraft strength with time. Any
storm that does go up this afternoon will be capable of producing
strong to severe wind gusts, due to high DCAPE values up to
1800-2000 J/kg. An outflow may move up into south-central AZ
later this evening from southeast AZ storms, but it will likely
take a very strong outflow to trigger additional activity in
northwest Pinal and Maricopa Counties.

Guidance shows boundary layer moisture will drop into tomorrow,
with afternoon dew point temperatures across the lower deserts
mostly in the mid-50s. This will result in lower SBCAPE values,
but surface temperatures will be slightly hotter and hi-res models
show weaker inhibition, if not uncapped, and slightly steeper
mid-level lapse rates. This may support slightly better coverage
of afternoon convection tomorrow versus today, but still focusing
primarily over the prominent terrain features. Strong to locally
severe wind gusts and blowing dust will be the primary hazard with
any storm tomorrow afternoon, with high DACPE values again. It
still may take one good outflow or multiple outflows and outflow
collisions to trigger storms near/in the Phoenix area.

&&

.LONG TERM /MONDAY THROUGH NEXT FRIDAY/...

Model uncertainty remains for the first half of next week,
primarily with respect to thunderstorm chances, as the position
of the high is likely to set up somewhere over eastern New Mexico
and western Texas by Monday. There is good global ensemble
consensus in a brief increase in moisture and instability Sunday
evening into Monday, most notably across southwest AZ and
southeast CA, but NBM forecast PoPs are mostly under 15% for the
lower deserts both days. At this point, we could continue to see
mostly slight chances favoring the high terrain into early next
week, but if moisture does eventually improve enough storm chances
are likely to be higher than what the NBM is depicting. By
Tuesday, drier air will filter back into the region as the
subtropical high begins to retrograde back over our region. This
will limit low end rain chances almost exclusively to the higher
terrain areas with the lower deserts remaining dry. By the latter
half of next week, the NBM shows PoPs being confined to the
Mogollon Rim with no chances for our CWA.

Temperatures are expected to continue to be more influenced by the
strong subtropical high as H5 heights hover between 593-596dm across
the Desert Southwest through early next week. Daytime highs are not
expected to change much from Sunday to Monday, barring any
significant change with the convective chances. As mentioned above,
by Tuesday the subtropical high will start to retrograde back to the
west and the center will eventually settle over AZ/NM during the
latter half of the workweek. The high is also expected to
strengthen to around 596-598dam during this time. The combination
of the center settling over our region and strengthening will
result in temperatures heating up to around 10 degrees above
normal for this time of year. Afternoon highs (morning lows) ware
forecast in the 110-116 (85-95) degree range across the lower
deserts and in the 100-110 (75-85) degree range across the higher
terrain areas. The increase in temperatures will also result in an
increase in HeatRisk, with widespread Extreme HeatRisk forecast
for the majority of the CWA by Wednesday. There is high confidence
already in the heat forecast for next week. So, the Extreme Heat
Warning was been extended through next Friday and will likely need
to be expanded to more areas by the middle of the week.

&&

.AVIATION...Updated at 2330Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation concerns are expected during the TAF period.
Winds will follow light and diurnal trends with speeds generally
aob 10 kt. There remains a slight chance (~20%) of an outflow from
distant convection moving through this evening, but the potential
remains too low to include mention of a boundary in the TAFs at
this time. SCT cloud decks will be present through much of the
forecast window, with the lowest bases around 10-12 kft.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected through Saturday
afternoon. Typical diurnal trends, along with overnight and early
morning VRB conditions, can be anticipated at the terminals, with
westerly flow switching to the southeast at KIPL, while KBLH
fluctuates between southwest and south-southeast. A decaying
outflow is possible at KIPL this evening, but the only impact
looks to be a reinforcement of westerly flow. Other than a FEW
mid and high level cloud decks, skies will be mostly clear.


&&

.FIRE WEATHER...
Hot and seasonally dry conditions are expected nearly every day,
through next week. Aside from a brief increase in moisture Sunday-
Monday, minimum RH values each afternoon will be around 12-18%
(15-25% Sun-Mon). Temperatures will range 5-10 degrees above
normal through the next week, with lower desert highs eclipsing
110 degrees most afternoons. There will be slight chances for
storms each afternoon through this weekend, but mostly favoring
higher terrain areas. Drier conditions, with lower storm chances
are expected by the middle of next week. Outside of thunderstorm
outflow winds, winds will follow the typical diurnal tendencies
with some modest afternoon upslope gustiness.

&&

.CLIMATE...
Record highs:

Date       Phoenix         Yuma         El Centro
----       -------         ----         ---------
Aug 21   114 in 2019    115 in 1969    117 in 1969
Aug 22   113 in 2011    115 in 1969    117 in 1969
Aug 23   114 in 2011    115 in 2011    116 in 1969
Aug 24   115 in 2020    119 in 1985    117 in 1985
Aug 25   113 in 2011    116 in 1962    117 in 1962
Aug 26   117 in 2011    115 in 2020    115 in 1981
Aug 27   114 in 2023    120 in 1981    117 in 1981
Aug 28   117 in 2023    118 in 2023    117 in 2009

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ530>555-559-
     560.

CA...Extreme Heat Warning until 8 PM PDT Friday for CAZ562-565>567-
     569-570.

&&

$$

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