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FXUS65 KPSR 081130
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
430 AM MST Mon Sep 8 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Overall dry conditions are expected this week with only slight
  chances for rain over the eastern Arizona high terrain late
  Wednesday into Thursday.

- Temperatures will stay within the normal range into mid week
  before cooling slightly late week.

- Localized Moderate Heat Risk is expected mainly across the
  south-central Arizona lower deserts into the middle part of the
  week with highs as warm as 105 degrees.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...
The current synoptic pattern shows the subtropical high centered
just off the coast of Baja with a closed Pacific low off the coast
of northern California. Dry air continues to spread eastward
through southern California into Arizona in between the two
weather systems. This dry air has thus far mainly stayed aloft
across our area, but over the next few days some of it will mix
down into the boundary layer lowering surface dew points into the
50s today areawide and into the 30s across the western deserts
starting Tuesday.

The residual lower level moisture was enough to bring some
isolated showers and thunderstorms yesterday, but this will be
even less likely to occur today. We can`t rule out a few isolated
afternoon showers or even a weak thunderstorm today, but overall
chances will be less than 10% across the entire area.

The subtropical ridge to our south has boosted heights across our
region since Saturday and today should bring the peak heights
allowing temperatures to heat up another 2 or 3 degrees across the
area. Forecast highs have trended upwards slightly for the first
half of this week with readings now likely to reach 101-105
degrees today and Tuesday across the lower deserts.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The Pacific low to our northwest will begin to expand and push
inland Tuesday into Wednesday with the low center stalling out
across northern California. The southeastern fringes of the larger
scale trough will eventually spread over our region by Wednesday
causing noticeable height falls. This will drive an increase in
winds by Wednesday with much of the area seeing afternoon wind
gusts to around 25 mph. Temperatures will also begin to lower on
Wednesday, more so across southeast California and southwest
Arizona where highs should drop to below 100 degrees.

As the trough gradually spreads over our region, southerly flow
will also increase briefly advecting some moisture northward into
eastern Arizona. PWATs will still be on the lower side at around
1.0", but with some weak upper level forcing moving into the area
it may be enough for some low end rain chances across the eastern
Arizona high terrain Wednesday night into Thursday.

Ensemble guidance is in fairly good agreement showing the low
center sagging farther to the south into the southern half of
California and/or into southern Nevada late Thursday before
lifting back to the northeast on Friday. This should bring even
lower heights over our region by Friday likely resulting in our
`coolest` day of the week with highs in the mid to upper 90s
across the lower deserts. Broad troughing is then expected to
somewhat stay over our region through the weekend and possibly
longer with a second Pacific low developing off the California
coast next weekend. This pattern should keep temperatures from
rising much next weekend with the latest NBM forecast highs
showing readings mostly in the upper 90s to around 100 degrees.
Guidance also shows even drier air filtering through the entire
area by next weekend pushing PWATs to as low as 0.5", or around
50% of normal for the period.

&&

.AVIATION...Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
There is moderate confidence that winds will remain westerly at
KPHX this morning, while other terminals see light variability to
a light east wind. West winds will prevail at all terminals by
late morning. Confidence is higher of an east wind developing
Tuesday morning at KPHX. Wind speeds during the day will mostly
stay between 5-10 kts, with a few afternoon breezes into the
teens. Skies will remain mostly clear with the exception of a FEW
CU with bases around 7-8 kft developing this afternoon. There is a
very low chance (

NWS Phoenix Office