656
FXUS65 KPSR 121733
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1033 AM MST Sat Jul 12 2025

.UPDATE...Updated 18z Aviation Discussion.

&&

.KEY MESSAGES...

- Temperatures will hover a few degrees above the daily normals
yielding widespread moderate HeatRisk through early next week before
cooling closer to the seasonal average during the latter half of the
week.

- Thunderstorm chances will slowly increase over eastern Arizona
higher terrain into early next week with chances and associated
impacts eventually descending into lower elevations by the middle of
the week.

&&

.SHORT TERM /Today through Sunday/...
Early morning objective analysis and WV imagery clearly depict a
pronounced subtropical anti-cyclone migrating westward off the
southern California coast with resultant W/NW flow over the forecast
area temporarily non-condusive for deep convection. With the highest
heights aloft shifting west, H5 values in a 592-595dm range will be
common over the forecast area the next several days; and numerical
guidance spread remains very narrow advertising readings 2F-4F above
normal yielding widespread moderate Heat Risk. The shallow moisture
advected into lower elevations yesterday (and to a lesser extent
early this morning) from a classic "Gulf surge" has been partially
scoured/mixed such that favorable 10 g/kg boundary layer mixing
ratios have been depressed mostly south of the international border.
As such, any thunderstorm development today should be relegated to
mountainous areas outside the CWA. By Sunday, a piece of the anti-
cyclone will begin to build into southern UT fostering better
synoptic scale flow while marginally better moisture profiles advect
westward from New Mexico. HREF membership suggests more concentrated
thunderstorm activity blossoming over E/SE Arizona which should
induce better organized outflows, albeit at a distance from the
forecast area, but likely still favorable towards importing a deeper
mixed, higher theta-e airmass into the CWA setting the stage for a
typical progression of monsoon impacts next week.

&&

.LONG TERM /Monday through Friday/...
During the first half of next week, subtropical ridging will
propagate back towards the four corners, however midtropospheric
heights should be further eroded by the combination of northern
stream jet energy in the Great Basin and a very distinct inverted
trough approaching through northern Mexico. Ensemble agreement is
actually quite good with respect to this evolution with uncertainty
primarily tied to the timing and exact location of the latter
mentioned inverted trough which could potentially materialize into a
slow moving closed low by the end of the week. During this synoptic
transition, deeper moisture profiles will slowly improve over the
region through both low level advection and midlevel residual
moisture shed from upstream convective complexes. Recent GFS BUFR
soundings suggest this moistening phase rather gradual with deep
boundary layer mixing ratios near 10 g/kg and total column PWATs
above 1.50" not settling over the CWA until Wednesday. Regardless,
this appears to align with a typical monsoon season progression
where mountain storms first send distant outflows into lower
elevations, then marginally moisture profiles support storms
beginning to encroach towards lower elevations with stronger
outflows and blowing dust impacts, and finally stronger, colliding
outflows sparking storms across a larger portion of the forecast
area. During this evolution, confidence is good that slightly above
normal temperatures early in the week will retreat close to the
seasonal normal by the middle of the week.

During the latter half of the week, the synoptic pattern should
become extremely favorable for both higher theta-e advection and
large scale ascent mechanisms. A large preponderance of model output
suggests the aforementioned inverted trough nearly stalling over
northern Sonora providing some vorticity forced ascent and a highly
divergent and optimal jet level wind profile. In fact, operational
models indicate an enhanced meridional jet developing over the CWA
which would encourage pronounced lift juxtaposed with plumes of
higher theta-e surging into Arizona. Whereas strong winds and
blowing dust would be the initial impacts early/midweek, this
pattern may evolve into one of a heavier rainfall/flash flooding
threat late in the week supported by deeper moisture profiles, warm
rain processes, and training rainfall scenarios. Forecast soundings
suggest an evolution towards more moist adiabatic thermal profiles
hitting a "sweet spot" of low level 12 g/kg mixing ratios, PWATS
1.50-1.75", and MUCape 500-1000 J/kg. Historically, these types of
synoptic and thermodynamic profiles have produced some of the larger
thunderstorm impacts for the forecast area. Interestingly, the 00Z
ECMWF is now producing a classic signal of possible morning storms
with a theta-e surge both Thursday and Friday indicative of strong
forced ascent. While these forecasts don`t always come to fruition,
this signal has occasionally been a precursor to some larger
convective and flash flood events around south-central Arizona, and
close attention will need to be paid to these days later next week.
Not surprisingly, temperature guidance spreads widen substantially
with the uncertainty of thunderstorm effects, however readings near
to slightly below normal should be common with the potential for any
morning/early afternoon storms to relegate readings below 100F in
some lower elevation communities.

&&

.AVIATION...Updated at 1733Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns will exist through Sunday morning under
mostly clear skies. Winds will follow typical diurnal trends for
this time of year, with afternoon gusts possible in the mid
teens. Lower confidence exists Sunday morning as to whether winds
obtain a true east component, possibly becoming light and VRB
instead, similar to the previous few mornings.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns through the TAF period under SKC skies.
KIPL will primarily stay out of the SE with winds generally AOB 10
kts, with a brief SW`rly component late this evening before
ultimately switch back out of the SE. KBLH will be S`rly with wind
speeds around 10-15kts diminishing to AOB 10 kts tonight.

&&

.FIRE WEATHER...
Above normal temperatures and primarily dry conditions will persist
through early next week before moisture increases and thunderstorms
chances blossom over higher terrain of eastern districts, then
eventually into lower elevation locations. Wetting rainfall chances
will initially be quite low with the greatest fire weather threat
being lightning with minimal rainfall amounts, however by the
middle of the week, more widespread storms with higher moisture
content will favor areas of beneficial rainfall, particularly in
higher elevations of eastern districts. Otherwise, minimum RH
levels will fall into a 10-20% range the next several days before
improving closer to a 15-30% range during the middle of next week.
Poor to fair overnight recovery of 20-50% will similarly improve
closer to a 30-70% range. Afternoon upslope gustiness 20-25 mph will
be common through the period with stronger thunderstorm outflow
winds becoming more prevalent next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...18
LONG TERM...18
AVIATION...Ryan/Whittock
FIRE WEATHER...18