470
FXUS65 KPSR 111025
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
325 AM MST Fri Sep 11 2026

.KEY MESSAGES...

- Extreme Heat Warnings continue across portions of southeast
  California and southwest Arizona through early evening while
  temperatures gradually cool into the weekend.

- Chances for scattered showers and isolated thunderstorms will
  continue to be focused mainly over the Eastern Arizona high
  terrain through the weekend before increasing in coverage and
  spreading into the lower deserts early next week.

- Near to slightly above normal temperatures are expected for this
  weekend and likely through the first part of next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Relatively quiet weather conditions will prevail today and likely
through Saturday. The subtropical ridge has weakened enough to
start a cooling trend today, but above normal temperatures will
still easily persist today. Extreme Heat Warnings for portions of
the western lower deserts continue through this evening with
highs from 106-110 degrees with even higher heat indices. The
lower heights and slight cooling aloft will help to bring daytime
highs across the south-central Arizona lower deserts to 103-106
degrees, or 3-4 degrees above normal. Today will also bring
limited convective potential with the subsidence inversion still
inhibiting convection over the lower deserts and to a decent
degree over the high terrain. The best potential (10-20%) PoPs
looks to be from late evening through the first part of the
overnight hours from Phoenix and areas east of Phoenix.

Saturday looks quite similar to today with moisture levels
remaining marginal enough to have a hard time overcoming the
subsidence inversion. Although the subtropical ridge will be
weaker and the center moves into New Mexico, it will still be the
dominant feature across the region. PoPs Saturday afternoon and
evening are still at most 10-20%, but increase Saturday night to
20-30% across the Phoenix area as there are indications of a weak
mid-level disturbance moving northward into southern Arizona. This
unfortunately is of high uncertainty at this point. However, if
some convection does get going Saturday night, forecast soundings
show 1000-1500 J/kg of elevated CAPE. We will have to watch for
any signs of the CAMs picking up on this potential as it could
result in some localized strong wind gusts and/or a low-end chance
of heavy rainfall. Temperatures Saturday are also anticipated to
drop another couple of degrees from Friday with lower desert highs
mostly between 102-106 degrees.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As stated last night, forecast uncertainty remains quite high for
storm potential for the first part of next week. Guidance is in
good agreement with the synoptic set up for Sunday through early
next week, but it`s the subtle mesoscale features that differ and
where the main uncertainty lies. Models are also in better
agreement with increasing moisture Sunday into Monday compared to
last night and this in turn is leading to higher forecast
instability and even PoPs. The ridge will continue to shift
farther to the east during this time as a trough moves into the
Northwestern U.S. The main shortwave within the trough will track
across the Northern Rockies, but the southern fringes of the
trough is still likely to bring increased support for showers and
thunderstorms by early next week. Models show a seasonably strong
upper level jet setting up from the Northern Rockies through the
Great Basin by Monday which is expected to place our region within
a favorable area for ascent as early as Sunday night and
potentially lasting through next Tuesday or Wednesday.

Other unknowns for early next week will be the placement of the
best moisture and likely the small swatch of the best instability.
It seems likely there will be considerable cloudiness somewhere
over or near eastern Arizona which will limit instability, while
the best instability/lower CIN sets up in a more cloud-free area
to the west (South-central AZ). There is also a decent chance of
having some sort of mesoscale disturbance tracking northward out
of Mexico at some point early next week which will help to
initiate storm activity. However, uncertainty is still too high to
be able to pinpoint the timing and the potential for storms, but
there is more optimism for at least one or two busy storm days
early next week. NBM PoPs have increased for early next week and
look fairly reasonable at anywhere from 30-70% across south-
central and eastern Arizona. If moisture and instability ends up
on the higher end of guidance, we are likely to have to worry
about some strong storms and heavy rainfall/flooding potential.
How long this increased rain potential may last is also uncertain
as models really don`t change the synoptic set up through at least
next Thursday or Friday. It`s doubtful we will have good rain
chances each day next week, but it also seems likely there will
not be any strong drying that will affect the area.

Temperatures next week are almost as uncertain as rain chances as
fairly high model spread is seen from Sunday-Wednesday, but with
at least a downtrend in temperatures. The latter half of next week
shows even higher spread, but with an uptrend in temperatures with
readings eventually warming back to above normal by next weekend.

&&

.AVIATION...Updated at 1000Z.

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

The only aviation weather issue will be low confidence on winds this
evening, with the possibility of a distant TS outflow causing sudden
gusty winds out of the SE or NE. A delayed southeast wind switch is
expected within the next couple hours at KPHX followed by a switch
back to SW/W between 17-19Z across all the terminals. Occasional
afternoon gusts to between 15-20 kts are likely. Chances for
TSRA/SHRA are too low (10% or less) to include in the TAF late
afternoon/evening. FEW-SCT and at times BKN mid and high cloud decks
will persist through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will continue to oscillate between SE and SW at the terminals
with speeds 8 to 15 kts sustained (periods with lower speeds likely
at KIPL). A few periods with gusts between 20-25 kts are possible at
KBLH this afternoon and this evening. The possibility of another
distant TS outflow reaching KIPL cannot be ruled out late this
afternoon/early evening. Periods with FEW-SCT and occasionally BKN
mid and high cloud decks will continue.

&&

.FIRE WEATHER...
Above normal temperatures will continue into the weekend, but
with some gradual cooling as humidities remain somewhat elevated.
Isolated chances for showers and a few thunderstorms can be
expected through the weekend, with the best chances over the
Arizona high terrain. Rain chances should improve during the first
half of next week with temperatures eventually dipping to around
average for mid September. MinRHs through early next week will
generally be between 15-25% across the western districts and
25-35% across the eastern districts. Winds will somewhat follow
typical diurnal patterns, but with more of a south southwesterly
predominant wind across the western districts. Daily afternoon
gusts of 20-25 mph will be common across the Lower CO River
Valley through the weekend before becoming more widespread early
next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ530-532-533.

CA...Extreme Heat Warning until 8 PM PDT Friday for CAZ562-566-567-
     569-570.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Whittock
FIRE WEATHER...Kuhlman