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 (

NWS Phoenix (PSR) Office