920
FXUS65 KPSR 152031
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
130 PM MST Wed Jul 15 2026

.KEY MESSAGES...

- Hot and muggy conditions will continue today, however temperatures
will cool into a near to below normal range by the end of the week.

- Shower and thunderstorms chances will increase today across
eastern and central Arizona with gusty winds and locally heavy
rainfall possible.

- Thunderstorms may become more widespread Thursday and Friday with
the potential for heavy rainfall and flash flooding.

&&

.SHORT TERM /Today through Friday/...
Expansive ridging aloft covers much of the Conus this afternoon
under a quasi-rex block pattern featuring a distinct easterly cutoff
low over central Texas bounded by high pressure arcing from the mid-
Atlantic to the northern plains, then into the Southwest. This
places the forecast area under deep easterly flow subject to
shortwave energy passing from the aforementioned Texas cutoff
towards the southern periphery of the high pressure ridge situated
over Arizona. This general pattern is typical for mid/late July,
albeit more amplified with stronger anomaly centers than is typical,
resulting in more impressive forcing mechanisms around the region.
Meanwhile, this synoptic pattern has allowed ample moisture to
stream into much of the CWA with boundary layer mixing ratios in a
favorable 10-12 g/kg range while total column PWATs exceed 1.50"
setting the stage for heavy rainfall potential with any slow moving
or training thunderstorms.

With the local environment recovering from convection Sunday and
Monday, the forecast area is situated in a fairly favorable location
for sustained thunderstorms with modest stretching and divergence at
jet level between well defined easterly waves/cutoffs over Texas and
western Mexico and a SW jet over the Great Basin. Forecast BUFR
soundings for this afternoon/evening suggest MLCape 500-750 J/kg
materializing after daytime heating and coincident with minimal
CinH. While the moistening of the boundary layer has reduced DCape
somewhat, values in excess of 1200 J/kg still appear probable
indicating robust outflows likely producing very gusty winds (albeit
largely sub-severe), blowing dust, and sufficient lift capable of
initiating new storms. The minimal inhibition may allow new storms
to form along a single outflow, however colliding outflows will be
more beneficial, and the preponderance of model output indicates
these collisions focused over western Maricopa County this evening.
Forward storm motion and influence from rapidly propagating outflows
should restrict the flash flood threat this evening, though
congealing storms could produce a localized threat.

The synoptic pattern will become even more conducive for robust
thunderstorms Thursday as at least one shortwave shed from the
aforementioned Texas cutoff progresses towards south-central Arizona
during peak heating. With convective debris and outflows pumping
additional moisture into the middle and lower troposphere, total
column PWATs 1.75-2.00" should be common while boundary layer mixing
ratios settle around 12-13 g/kg by Thursday afternoon. This moisture
profile should result in a near equal MLCape/DCape balance in a
"sweet spot" of 1000-1500 J/kg historically present during big
monsoon thunderstorm events. Convective inhibition should be nearly
absent late afternoon/early evening, and with underlying deep layer
ascent, it should only take weak outflows to initiate additional
storms. Intersecting outflow boundaries are also likely with
consolidating storms over parts of the CWA resulting in heavy
rainfall and flash flooding. Rainfall rates at least 2-3"/hr appear
likely given the moisture profiles, and a Flash Flood Watch has been
issued for south-central Arizona counties. At this point, HREF and
global model output suggests northern Pinal and SW Maricopa counties
as the focus for the heaviest rainfall.

Considerable forecast uncertainty exists Friday contingent upon the
strength and expanse of thunderstorms Thursday night. A large subset
of modeling indicates the atmosphere becoming completely overturned
by storms and outflows Friday morning with forecast soundings
depicting a classic, post-event moist adiabatic profile. Should this
come to fruition (better than a 50% chance), convective potential
the remainder of Friday would become minimal, at best, given the
combined extensive cloud cover and poor lapse rates resulting in
essentially no instability. A slight alternative outcome is hinted
at by recent operational ECMWF and NAMNest output which suggests a
well defined MCV juxtaposed with a pool of higher theta-e advecting
north through the Phoenix metro Friday morning. While these type
model forecasts with morning storms forced by an MCV and copious
deep moisture are common during the monsoon, they only come to
fruition occasionally every summer, but when this scenario unfolds,
very efficient rain rates and flooding ensues. Regardless, the
strongest model evidence indicates only small pockets of instability
remaining Friday afternoon, and have cut mandated NBM POPs
substantially as even the most aggressive modeling that always
forecasts storms has little convective response Friday
afternoon/evening.

&&

.LONG TERM /Saturday through Tuesday/...
Moderate forecast uncertainty is still an issue for this weekend
into next week as day-to-day shower and thunderstorm chances are
likely to persist. Some slight drying over the weekend, as the
easterly wave to our east southeast gradually weakens, is likely to
bring lower rain chances compared to Thursday and Friday, but that
does not mean it will not be active in some areas. As of right now,
guidance is favoring the Arizona high terrain this weekend with
daily PoPs of 50-70%. An easterly steering flow is also likely to
persist which will enable at least some chances (20-30%) of showers
and storms into the lower deserts this weekend. Lingering ascent
also looks possible this weekend from the easterly wave, although
this is more likely to benefit far southeast Arizona and northern
Mexico.

Model uncertainty increases further during the first half of next
week as guidance is shifting where the subtropical high center may
be and whether or not another easterly wave will impact our region.
There seems to at least be some agreement in gradually shifting the
high center southwestward to somewhere over the Central Rockies or
Central Plains Sunday into Monday, but where it goes thereafter is
much more uncertain. The GEFS favors the high center settling
anywhere from the Four Corners area to into central New Mexico,
while the EPS shows it more over New Mexico into western Texas. The
first half of next week is still likely to be fairly active as far
as storm potential, and could even be very active if the easterly
wave becomes a big factor. However, the latter half of next week may
involve a decrease in monsoon activity if the high center truly
moves closer to or into Arizona.

NBM temperature trends show below normal temperatures lasting
through the weekend for much of Arizona and likely persisting but
gradually warming through the first half of next week. Locations
across southeast California and southwest Arizona should see
temperatures right around normal with most days seeing little
monsoon convection.

&&

.AVIATION...Updated at 1800Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Gusty outflow winds along with TS impacts will be the main aviation
concerns during the forecast period. Multiple boundaries look
possible this evening sometime between 23-03Z, though what direction
they may originate from remains uncertain at this time. Elected to
keep TAFs consistent from the previous forecast to prevent frequent
planning changes, but the forecast will likely change over the next
several hours so multiple updates should be expected. VCTS/TS will
follow soon after, but there is low confidence surrounding direct
impacts at the terminals. PROB30 groups remain at each site to
account for this uncertainty. What direction winds will favor after
this initial wave of activity will depend heavily on the direction
of the dominant outflow. In the meantime, winds will follow familiar
diurnal trends with perhaps some occasional afternoon gusts in the
mid to upper teens.

Lingering VCSH/VCTS may stick around through 09Z, but where this
activity sets up and its residence time is another forecast
uncertainty. This second round should be relatively less impactful
than the previous convection, but could result in reduced VIS under
heavier rainfall and erratic winds. The expectation at this time is
that extended periods of VRB conditions will occupy most of the
morning hours.


Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected during the next 24 hours.
SE winds will be common at KIPL, though a brief switch of the W/SW
this evening can`t be ruled out. S/SW`rly winds will prevail at KBLH
with a brief window of gusts around 25 kt overnight. Mostly clear
skies will give way to increasing mid-level clouds tonight into
Thursday morning.

&&

.FIRE WEATHER...
Active monsoon weather with elevated moisture levels will continue
through the rest of the week. Shower and thunderstorm chances will
increase over the eastern districts today through Thursday with only
isolated chances over the western districts. Heavy rainfall will
also be possible across the eastern districts by Thursday afternoon.
MinRHs will improve from east to west over the next few days,
increasing from 20-35% today to 30-50% by Friday. Outside of
potential thunderstorm outflows, winds for the eastern districts
will tend to be light and somewhat favor diurnal trends.
Winds will predominately favor the south while becoming breezy
starting Thursday across the western districts.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Thursday for AZZ530-532.

     Flood Watch from Thursday afternoon through late Thursday night
     for AZZ534-537>563.

CA...Extreme Heat Warning until 8 PM PDT Thursday for CAZ562-563-
     565>567-569-570.

&&

$$

SHORT TERM...18
LONG TERM...Kuhlman
AVIATION...RW
FIRE WEATHER...Kuhlman