675
FXUS65 KPSR 031150
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
450 AM MST Thu Sep 3 2026

.UPDATE...Updated 12Z Aviation Discussion.

&&

.KEY MESSAGES...

- Isolated showers and thunderstorms will be possible across South
  Central Arizona late this afternoon.

- Tropical moisture will arrive into the region tonight into Friday,
  further increasing rain chances mainly across the foothills and
  high terrain areas east of Phoenix before chances shift into
  Southwest Arizona and Southeast California this weekend.

- Temperatures remain in a near to below normal category for the
  rest of this week and into the weekend, resulting in widespread
  Minor Heat Risk and localized areas of Moderate Heat Risk.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
Latest GOES-18 mid-lvl wv imagery and 500 mb streamline analysis
reveals a broad trough of low pressure encompassing the Pacific NW
and Intermountain West while a ridge of high pressure extends from
the Southern Plains into the southeastern U.S. Our forecast area is
situated between both of these features under a prominent fetch of
dry SW flow aloft. Meanwhile, now Cat 2 Hurricane Marie is churning
over the E Pacific, well southwest of the tip of the Baja Peninsula.
Moisture advection is ongoing well out ahead of the main circulation
into N Sonora MX and beginning to encroach on southern AZ. Moisture
will continue to be transported nwd into central AZ with PWAT values
expected to climb to around 1.5-1.7" later today through early
Friday, however there is expected to be a well defined moisture
gradient from E to W across AZ. Much drier air associated with the
troughing to the NW of our region will extend into SE California and
southwest AZ through Friday which will really limit rain chances
across the western half of the forecast area until better moisture
arrives this weekend. NBM PoPs have continued to shift ewd with each
subsequent run and the main focus for shower and storm activity now
looks to be east of Phoenix, mainly in the foothills of Maricopa
County and S Gila County. This aligns with the latest WPC ERO for
Day 2 (Friday) with an eastward shift in the slight risk which
mostly encompasses the TWC forecast area and clips S Gila County.
Nonetheless, CAMs still indicate a few pop up isolated showers and
storms in central Maricopa County including the Phoenix Metro area
late today through early Friday and again Friday afternoon/evening.
Some storms could produce gusty wind and localized flash flooding.

Due to the presence of troughing to our west maintaining 500 mb
hghts within a 587-590 dam range, temperatures will be within a
degree or two of daily normals through the end of this week. Lower
desert highs will generally range from the upper 90s to around 105
degrees each afternoon, following morning lows from the upper 70s to
middle 80s. The West Coast trough will also promote a tighter mid
lvl pressure gradient over southeast CA and western AZ which will
lead to continued breezy to locally windy conditions across the
Imperial and Lower Colorado River Valleys. Gusts could reach upwards
of 25-30 mph in the aforementioned areas and potentially as high as
40 mph in far SW Imperial County.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Global models are coming into somewhat better agreement with the
pattern evolution this weekend. Both the ECMWF and GFS show high
pressure strengthening over the southern Plains with the western
periphery of the ridge extending over E AZ and NM. This will cause
the subtropical jet to shift wwd beginning Saturday, setting up
better moisture advection over southeast CA and southwest AZ. NBM
PoPs are still not overly impressive, mainly in the 20-30% range
on Saturday, however the GEFS/GFS indicates a final slug of
moisture from Marie being pulled into southeast CA on Sunday with
PWATs rising above 2.0". Therefore we will have to monitor for
heavier rainfall potential in portions of SE California including
Joshua Tree NP on Sunday. Elsewhere, across southcentral AZ, rain
chances look to be meager due to more extensive cloud cover and
very low instability. The latest WPC QPF field shows a local
minimum in rainfall totals (<0.10") in southcentral AZ including
the Phoenix Metro through this weekend. By early next week, there
are large discrepancies in the ridge/trough positioning which will
complicate the precipitation forecast, but there will still be
adequate moisture across our region which will keep low end PoPs
in place across eastern and southeastern AZ Monday and Tuesday
with potentially better precipitation chances arriving Wednesday.

The temperature forecast this weekend into early next week remains
largely unchanged, although there will likely be a gradual increase
from near normal temperatures on Saturday to slightly above normal
temperatures Sunday into early next week as ridging strengthens over
the region. Depending on how strong the ridge gets, NBM temps could
climb a few more degrees in subsequent runs and it is not out of
the question that we could see lower desert highs approaching 110
degrees as indicated by the NBM 75th percentile on Monday and Tuesday.

&&

.AVIATION...Updated at 1150Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation concern this TAF period will be the possibility
of VCTS/TSRA/VCSH this evening and during the overnight/early
morning hours on Friday. Winds will tend to favor diurnal trends
with a slower than usual turn to westerly flow, resulting in a
window of southerly crosswinds at KPHX and KDVT later this
morning. Hi-res guidance is hinting at TS developing in the
southern and eastern portions of the airspace during the late
afternoon/early evening hours with perhaps some cells migrating to
within the vicinity of the terminals. KIWA is the most likely
(20-30% chances) to see VCTS, but nearby convection cannot be
ruled out for the other sites. However, chances are too low (<20%)
to warrant inclusion of even VCTS at this time for KPHX, KDVT,
and KSDL. Hi-res guidance is also hinting at some additional
SHRA/TSRA developing during the overnight/early morning hours
within the airspace. VCSH has been included in the TAFs for now,
but confidence is low in this occurring. The activity may stay to
the east of the terminals. FEW- SCT cloud decks around 8-12 kft
are expected through the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:
Breezy conditions, once again during the afternoon and evening,
hours will be the main aviation concern. Winds this morning will
be aob 10 kt, with some variability being observed at times,
mainly at KBLH. Flow will contain some degree of a westerly
component at KIPL while KBLH switches between southerly and
southwesterly directions. Mostly clear skies will be common over
the region.

&&

.FIRE WEATHER...
Isolated to widely scattered showers and storms will be possible
in southcentral AZ later today through Friday. Rain chances will
expand westward through this weekend, becoming focused over the
western districts Saturday and Sunday. The best chances for
wetting rainfall will be over the higher terrain areas of eastern
and southeastern AZ. Afternoon minimum humidities will range from
7-15% across southeast CA and between 20-35% for the remainder of
the region through Friday and will likely increase above 25%
areawide this weekend. Overnight recoveries will range from poor
across the western deserts and good to excellent across the
eastern districts. Daytime winds will remain elevated out of the
south to southwest, with the strongest gusts in Southeast CA and
along the Lower Colorado River Valley peaking between 20-30 mph
during the afternoon/early evening.

&&

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

$$

SHORT TERM...Salerno
LONG TERM...Salerno
AVIATION...Berislavich/RW
FIRE WEATHER...Whittock/Salerno