146
FXUS65 KPSR 240550
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1050 PM MST Sun Aug 23 2026

.UPDATE...Updated 06z Aviation Discussion...

&&

.KEY MESSAGES...

- Isolated to scattered thunderstorms, some strong to severe, are
  expected this evening across south-central Arizona.

- Increasingly less favorable conditions for thunderstorms will
  develop starting Monday with virtually no chances for rain from
  Tuesday through the rest of the week.

- High temperatures will reach or exceed 110 degrees nearly every
  day this week and will be near daily records, while morning
  lows remain unusually warm.

- Extreme Heat Warnings are in effect through Saturday with daily
  Major to Extreme HeatRisk.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
Some upper level jet support and mid-level gravity waves helped
spark off a line of high-based scattered showers and storms
across southwest AZ this morning. This activity has since weakened
and dissipated. Surface-based moisture has also increased across
southwest AZ and areas south of I-8. Dew point temperatures at
midday in Yuma County to western Pima County were up to 65-75
degrees. This moisture return in southern AZ will likely help
fuel later afternoon and evening thunderstorms. Overall, model
guidance still suggests this afternoon through this evening
becoming a somewhat busy monsoon period.

Outside of southern AZ, where the best moisture return was,
boundary layer conditions remain similar to the past couple of
days with sub-optimal moisture (mixing ratios around 8 g/kg) and
limited instability (few hundred J/kg MLCAPE). Initially through
much of, if not all of, this afternoon storms should favor higher
terrain areas, including portions of La Paz County, and it may
even look like it will not become active at all. However, hi-res
guidance continues to show the best time period for activity
across south-central AZ coming around and after sunset. Guidance
shows storms being a bit slower to develop in Pima County, but
when they do they do they will have the best potential to become
strong to severe, tapping into the best moisture and instability.
The storms to the south this evening will then be capable of
pushing one or multiple strong and dusty outflows northward into
south-central AZ, which may then trigger additional storms. Some
hi-res model runs also suggest outflow collisions may occur, with
outflows also from the north, but confidence in outflows coming
down from northern AZ is low. Additionally, there are indications
the storms to the south may develop into an MCV and track
northward through Phoenix this evening. Strong to locally severe
wind gusts will be the primary weather hazards, with very high
DCAPE values up to 1800-2000 J/kg. Localized flash flooding may
also become a threat with any slow-moving storms or training of
storms, with the best potential southwest of Phoenix where
moisture will be highest.

Convective chances for Monday are even more uncertain as guidance
generally shows at most a 10% chance despite moisture and
instability being better than today. However, subsidence will be
much stronger on Monday as the subtropical ridge begins to move
westward back into our region. We will have to wait until tonight
to have a better idea on the storm potential for Monday, but it
does seem to be considerably lower than this afternoon/evening.

Temperatures today will again be right near record highs with
lower desert readings from 110-115 degrees. The increased boundary
layer moisture expected for Monday should hold daytime highs down
a bit with NBM forecast highs currently between 106-111 degrees,
but heat indices will mostly match what are expected today.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Forecast attention turns away from monsoon storm potential and
back toward the extreme heat conditions starting Tuesday. The
subtropical high center will continue to shift westward into our
region into the middle part of the week with the center likely
settling somewhere over southern Arizona from Wednesday through at
least Friday or Saturday. Forecast H5 heights are also shown to
reach 594-597dm for the latter half of the week which places it
just shy of climatological records for late August. NBM
temperature guidance remains quite consistent showing highs rising
into a 112-116 degree range for the latter half of this week as
conditions dry out. Daily temperature records in Phoenix will
continue to be in jeopardy through the entire week, but are likely
to fall short in Yuma and El Centro. Once the high center moves
overhead by Wednesday, rain chances will essentially go to 5% or
less. As of now, conditions for any monsoon storm activity do not
look good through next weekend.

&&

.AVIATION...Updated at 0550Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Gusty winds and SHRA/TSRA activity in the vicinity during the next
couple of hours will be the main aviation weather concern
throughout the TAF period. SHRA/TSRA activity, with the greatest
concentration to the southwest of the terminals will continue
through 07Z, with VCSH lingering a bit longer into the overnight
period. Wind directions through at least the first part of the
overnight will continue to remain erratic due to convective
activity nearby before becoming light and variable to light
easterly by sunrise through early Monday morning before shifting
out of the west by the late morning hours. Much quieter conditions
are expected on Monday with no threat of outflows/thunderstorms.
SCT-BKN mid to high clouds will continue through the overnight
period before coverage decreases to FEW-SCT during the day Monday.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns under FEW-SCT mid/high cloud decks can
be expected throughout the TAF period. Winds will generally be out
of the southeast at KIPL and will fluctuate between the south-
southeast to southwest at KBLH. Overall wind speeds will range
between 8-15 kts, highest at KBLH.

&&

.FIRE WEATHER...
Hot temperatures will prevail through the entire week with shower
thunderstorm chances mainly today and possibly Monday. Strong
gusty winds will be possible late this afternoon and evening with
any thunderstorms, while chances for wetting rains will remain
below 20%. Minimum RHs will improve through Monday with readings
of 15-25% today and 20-30% Monday, before dropping back into the
teens into the middle part of the week. Temperatures will be
around 5-10 degrees above normal, with lower desert highs
eclipsing 110 degrees nearly every afternoon. 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 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
Aug 29   116 in 2023    117 in 1954    117 in 2005

&&

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

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

&&

$$

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

NWS Phoenix (PSR) Office