659
FXUS65 KPSR 170454
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
954 PM MST Thu Oct 16 2025

.UPDATE...Updated 06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Dry and tranquil weather conditions with zero rain chances will
  prevail through the weekend with temperatures remaining below
  normal.

- Temperatures will warm back into the near normal range for early
  next week with rain chances potentially returning to at least
  the Arizona high terrain during the middle of next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Early afternoon water vapor satellite imagery shows the upper-
level trough that brought active weather to portions of the
western CONUS earlier this week situated over the northern Rockies
with the Desert Southwest under continued cyclonic flow aloft.
Westerly flow aloft continues to advect a dry air mass into the
region with PWATs now below 0.5", thus dry and tranquil conditions
with mostly clear skies will prevail into the weekend. The below
normal height anomalies will continue to keep temperatures a good
5-8 degrees below normal through Friday with afternoon highs
topping out in the low to mid 80s across the lower deserts with
early morning lows bottoming out in the 50s across most areas. By
Saturday, an upper-level ridge will begin to build over the region
as an upper-level trough builds off the coast of the northern
Baja Peninsula, marking the beginning of a warming trend.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The first part of next week should see a weak ridge extending from
central California through the Desert Southwest, while the trough
energy that sinks to our southwest earlier in the weekend forms a
cut-off low. Models are in good agreement with this cut-off low
formation and eventually drifting it back to the north northeast
toward southern California by around next Tuesday/Wednesday. The
ridging over our region early next week is expected to push
temperatures back into the normal range with highs in the mid to
upper 80s across the lower deserts Sunday and Monday before
beginning to cool again as early as Tuesday.

Where models begin to diverge is seen within moisture fields as
the cut-off approaches our region. Both the GEFS and EPS do
showing moisture increasing Tuesday into Wednesday, but the GEFS
only shows PWATs returning to 100-110% of normal across eastern
and central Arizona whereas the EPS shows PWATs increasing to
150-170% of normal. This discrepancy is fairly significant and
is leading to high uncertainty in PoPs for the middle of next
week. If the system is closer to the GEFS solution, then any rain
chances should mostly be across Arizona high terrain areas, while
the EPS would have chances easily extending into at least the
south-central Arizona lower deserts. Either way, potential
rainfall amounts are expected to be on the lighter side. Both
ensemble suites eventually show the cut-off low quickly weakening
as it moves northeastward through our region around next Wednesday
and Thursday. The weather system may also lead to a brief dip in
temperatures during the middle part of next week, but for now they
are not likely to fall much below normal.

&&

.AVIATION...Updated at 0455Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
Light winds (AOB 7 kts) will prevail. Winds, across the Greater
Phoenix Area, will generally follow their typical diurnal
tendencies with extended periods of light and variable to nearly
calm conditions. Wind directions will vary between north and west
at KIPL and KBLH. Skies will remain mostly clear.

&&

.FIRE WEATHER...
Dry, tranquil weather with below normal temperatures will prevail
through the end of the week. Minimum afternoon humidity levels
will generally fall into a 15-25% range across the lower deserts
to upwards of 30-35% over the eastern Arizona high terrain.
Overnight recovery will be good to excellent. Light diurnal winds
are expected across the eastern districts, while some occasional
breezy northerly winds will be seen across the western districts.
Similar weather conditions are likely to persist for the first
part of next week with temperatures returning to normal.

&&

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

$$

SHORT TERM...Lojero
LONG TERM...Kuhlman
AVIATION...Berislavich
FIRE WEATHER...Kuhlman