591
FXUS65 KPSR 291742
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1042 AM MST Mon Dec 29 2025

.UPDATE...Updated 18Z Aviation Discussion.

&&

.KEY MESSAGES...

- High pressure will spread into the region early this week
  resulting in dry and locally breezy conditions with temperatures
  slightly above normal.

- An unsettled weather regime moving into the region during the
  latter half of the week will lead to periods of increased light
  rain chances.

&&

.SHORT TERM /Today through Tuesday/...
The remnants of a shortwave trough are now shifting southwest of
the region with ridging beginning to move in from the southeast
and from the northwest. A strong surface high pressure system over
the Great Basin will help to maintain a strong pressure gradient
across central Arizona into southern California today into
Tuesday. This will result in northerly breezy conditions across
the Lower CO River Valley and northeast to easterly breeziness
across eastern and south-central Arizona. Temperatures will also
begin to recover today with highs reaching near 75 degrees in the
Phoenix area to around 70 degrees across the western lower
deserts. Similar readings are forecast for Tuesday despite
increasing high clouds.

&&

.LONG TERM /Wednesday through Sunday/...
The main forecast concern for the the latter half of the week will
be the dramatic increase in moisture Tuesday into Wednesday and
eventually some rain chances by Wednesday evening. The remnant
energy from the shortwave that is currently moving to the
southwest is expected to merge with a cut-off low well west of
Baja. This will help to reinvigorate the cut-off low by Tuesday
and to allow it to begin to move back to the northeast starting
Tuesday night.

Increasing southerly flow will develop across northern Mexico and
eventually into our region on Tuesday sending moisture northward.
Upper level moisture will be first to spread into our region
creating fairly cloudy skies by Tuesday night with low and mid
level moisture increasing on Wednesday. PWATs are forecast to
quickly rise from near seasonal normal today to 250-300% of normal
by late Wednesday. Light showers should become possible from
southwest to northeast across the area starting Wednesday
afternoon, but forcing will be quite limited. The peak of the
forced ascent should occur during the first half of Thursday with
rain chances of 50-70% over much of the area. Shower chances
should diminish across the western deserts by Thursday evening and
then through Arizona during the overnight hours Thursday night.
Expected rainfall amounts are still a bit uncertain, but due to
the overall weak forcing most lower desert areas should stay
between 0.05-0.20" while the more favored upslope areas north and
northeast of Phoenix may see 0.25-0.50". Upper level ridging is
forecast to move over the region Thursday night into Friday with
considerable drying occurring aloft. Some lingering light shower
chances may stick around into Friday across the eastern Arizona
high terrain, but this should result in little if any additional
rainfall.

Guidance shows another upper level trough approaching the west
coast of California on Friday, but the current track is likely to
mostly bypass our region to the northwest next weekend. The NBM
is still trying to suggest this may bring another round of rain
chances, but that seems to be a stretch so PoPs have been reduced
by nearly half for Saturday and Sunday. Forecast high
temperatures are expected to dip later this week, but readings are
likely to stay 3-5 degrees above normal most days. Overnight
temperatures will become quite mild starting midweek with lows
mostly in the 50s due to the the cloudy skies.

&&

.AVIATION...Updated at 1740Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns expected through the TAF
period. Elevated E/NE winds are expected this afternoon, with
gusts into the upper teens to around 20 kt expected. Winds will
relax slightly after sunset, but remain generally aob 10 kt
through the remainder of the period. SCT high cirrus clouds are
expected through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected through the TAF period.
Winds at KBLH are expected to maintain a northerly component
through the period, with speeds generally aob 10 kt, with some
gusts up around 20-25 kt this afternoon. At KIPL, northerly winds
are expected through this afternoon, then this evening (~04Z)
winds will go westerly. Speeds at KIPL, will generally be aob 8 kt
through the period. Increasing mid and high level clouds are
expected through the period.

&&

.FIRE WEATHER...
Dry weather with slightly above normal temperatures will be seen
early this week with minimum humidity levels in a 20-30% range.
Enhanced north to northeast winds will be common through Tuesday,
particularly across ridge tops of eastern districts where gusts
of 20-30 mph are expected today. Moisture will begin to seep back
into the region by Wednesday raising humidities and bringing rain
chances late Wednesday and Thursday.

&&

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

$$

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