740
FXUS65 KPSR 131110
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
410 AM MST Sat Sep 13 2025

.UPDATE...Updated Aviation Discussion

&&

.KEY MESSAGES...

- Near to slightly below-average temperatures this weekend before
  gradually warming through early next week.

- No showers or storms expected this weekend through early next
  week, with mostly sunny skies and light winds.

- Potential for an increase in rain chances late next week with a
  push of moisture, but this forecast is still highly uncertain.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...
It was an active afternoon yesterday across eastern AZ with
isolated to scattered organized strong to severe thunderstorms,
including some supercells, and storms are still popping up early
this morning. This activity was and is being driven by a trough
pushing through the West. The base of the trough is seen on WV
satellite early this morning pushing into AZ. With the dry
westerly flow across the base of the trough, monsoon moisture is
slowly being scoured out. Phoenix yesterday afternoon dropped from
a dew point temperature of 60 down to 30 in 5 hours and most of
the Phoenix area is sitting in the 30s to lower 40s dew point this
morning. Mesoanalysis also shows 100mb mean mixing ratios have
fallen to 5-6 g/kg for south-central AZ to southeast CA, with the
remaining monsoonal moisture pushed to primarily southeast AZ. As
drying continues today, storms will be confined to southeast AZ,
mainly White Mountains and points south. The trough will enter
into NM Sunday and the monsoonal moisture will be even further
suppressed, even to south of AZ completely. NBM PoPs drop to 0%
in southern Gila County by this afternoon and will remain at 0%
across the entire local CWA through Sunday, with mostly clear
skies and lighter winds as well.

The combo of this passing trough, suppressing heights over the
region, mostly clear skies, and dry conditions will result in
cooler temperatures across the region, especially at night where
radiational cooling will help temperatures in the lower deserts
dip into the low to mid 70s the next few mornings. Some rural
communities are even forecast to drop below 70 degrees the next
couple mornings. For some locations, these will be the coolest
ambient low temperatures since the end of May to start of June.
So, mornings this weekend will be much more pleasant and
refreshing. High temperatures this weekend are forecast to come up
shy of daily averages, with most lower desert locations only
reaching the middle to upper 90s. Despite this refreshing change,
it is still good to practice heat safety in the afternoons. Long
exposure to 90 degree heat in full sun can have negative effects
without proper heat safety.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Heading into the beginning of next week, following the passage of
the trough this weekend, the synoptic pattern across the Desert
Southwest will enter a relatively weak westerly to southwesterly
flow regime, with high pressure ridging nudging back into the
area and H5 heights gradually rising. Global ensembles support H5
heights going from 582-582dam today to 588-590dam by Tuesday,
which is slightly above normal for this time of year. As a result,
this trend will allow temperatures to remain near seasonal levels
through at least Monday and then temperatures are forecast to
rise to or slightly above daily averages on Tuesday and Wednesday,
with lower desert highs forecast to reach the lower 100s.

This weaker flow pattern through early next week will allow for
at least a slow return of PBL moisture from the southeast, with
PWATs forecast to climb back to normal to slightly above normal
during the first half of next week. However, afternoon shower and
storm chances during the first half of next week will mostly
favor Southeast AZ, with NBM PoPs across South-Central AZ to
Southeast CA at or below 10% through Wednesday.

There still remains a high degree of variability in the forecast
for late next week, largely due to uncertainties in the magnitude
of moisture advection and potential showers and storms. There is
at least good confidence that tropical moisture will move up the
western coast of Mexico, along and west of Baja, with highest PWAT
anomalies favoring SoCal and just offshore by Thursday. While the
ensemble mean PWAT forecasts for the 3 primary global models are
pretty similar in magnitudes, each model still has large spreads,
with interquartile ranges up to 0.5 inches. The 25th percentiles
though, do have well above normal PWATs spreading across the
region, which is a good sign for shower and storm chances. There
is also the question of forcing for shower and storm development.
Given the overall weak synoptic pattern heading into late next
weak forcing may be very limited, unless shortwaves not yet
resolved in modeling can move through or troughing further up the
west coast can play a role. Latest NBM forecast has rain chances
going up starting Thursday in the western deserts and then
widespread 30% PoPs on Friday. Ultimately, it is still too early
to know what to expect. On the high end of the spectrum there
could be flooding rains while the other end may just be thick
clouds and little or no rain at all.

&&

.AVIATION...Updated at 1110Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT, and
No aviation concerns are expected through Sunday morning under
mostly clear skies. Winds will follow familiar diurnal trends,
with extended periods of variability, especially for the western
terminals. Speeds will remain generally less 10 kts, with perhaps
a few afternoon gusts in the mid-teens for the Phoenix metro
sites.

&&

.FIRE WEATHER...
Near to slightly below normal temperatures will be common across
the region through this weekend thanks to an area of low pressure
passing to the north. Outside of some breezy conditions this
afternoon in eastern districts, with peak gusts up to 20-25 mph,
winds will be light over the next several days and directions will
favor familiar diurnal trends. Dry conditions are expected through
the first half of next week with no chances for wetting rains.
MinRHs this weekend through early next week will mostly range
from 15-25% across all districts with fair overnight recoveries at
30-50%. Certain details of the forecast for the second half of
next week are still highly uncertain, but a push of moisture into
the region is anticipated and could lead to better rain chances.

&&

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

$$

SHORT TERM...Benedict
LONG TERM...Benedict
AVIATION...RW
FIRE WEATHER...Benedict