805
FXUS65 KPSR 121220
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
520 AM MST Wed Mar 12 2025

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
The unsettled pattern will prevail through the remainder of week,
bringing cooling temperatures and additional precipitation
chances. A potent weather system will move through the region on
Thursday bringing a strong cold front through the region.
Widespread showers and isolated thunderstorms are expected with
the cold front, while windy conditions are likely for much of the
day on Thursday. A second much weaker weather disturbance is then
likely to bring light showers across the Arizona lower deserts and
higher elevation light snow later Friday through Friday night.
Starting Sunday and Monday, drier and warmer conditions take hold
across the region with highs briefly warming into the lower
eighties on Monday.

&&

.DISCUSSION...
Early morning shower activity is expected to quickly wind down
across higher terrain areas as the weakening shortwave trough
gradually exits eastward into New Mexico. However, some isolated
very light showers will remain possible mainly across the higher
terrain northwest and north of the Phoenix area through the
evening hours as somewhat moist upslope flow remains in place.
Elsewhere, expect gradual decreasing clouds today with highs
falling just short of normals.

Attention then turns toward the next weather system quickly
approaching from the northwest today into Thursday. This next
upper level trough will be quite strong and it will maintain its
strength or even strengthen further as it pushes into our region
on Thursday. The NAEFS continues to show H7 and H5 heights and
temperatures reaching near climatological MINs for much the
Interior West with this incoming trough. Upper level dynamics will
be fairly strong as the main shortwave trough pushes across
southern California into Arizona on Thursday, in addition to a
well-defined cold front with H8-H7 winds of 45-55kts associated
with the front. The main forecast concern with this incoming
weather system will be the strong winds during the afternoon and
early evening hours with gusts likely peaking between 40-50 mph
over a good portion of the area. A Wind Advisory has been issued
for the entire area focused on Thursday afternoon and lingering
into the evening across the western deserts and the Arizona higher
terrain.

Cold frontal induced showers are likely to push into southeast
California during mid morning Thursday, while southerly winds
increase elsewhere across southern and central Arizona. Winds are
likely to start gusting to around 30-35 mph by late morning well
ahead of the frontal band with some areas of blowing dust
becoming possible. Winds should continue to strengthen into the
afternoon hours with advisory level wind gusts over 40 mph in many
locations. As the front continues to march to the east through
western Arizona early in the afternoon, we may begin to see some
embedded thunderstorms develop mainly along the leading edge. Any
stronger showers or thunderstorms will be capable of mixing down
even stronger winds in excess of 50 mph. Hi-res guidance also
begins to show some line segments, likely associated with
thunderstorms, developing as the frontal rain continues into
south-central Arizona mid to late afternoon. If this were to
occur, a few locations could see winds reaching severe limits.
This line of showers and isolated thunderstorms should only last
two to three hours max with the Phoenix area likely seeing the
peak rain and wind between 2-5 pm. Winds behind the frontal band
are also likely to strengthen across southeast California and
southwest Arizona later in the afternoon and last through early
evening with advisory level wind gusts of 40-50 mph likely. QPF
amounts are largely unchanged from previous forecast packages with
generally under 0.2" expected across much of southeast and
southwest Arizona, between 0.3-0.5" in the Phoenix area, to a bit
more than 0.5" across the higher terrain.

Snow levels will also be plunging during the evening hours behind
the cold front, dropping to near 4000 feet by late evening.
However, the bulk of the expected precipitation is expected to
fall by early evening across the higher terrain east of Phoenix.
Rain should change over to snow above 5000 feet by early evening
with accumulating snows of between 2-5" possible through the rest
of the overnight hours. A dusting to maybe an inch or so will be
possible between 4000-5000 feet. A Winter Weather Advisory for
elevations above 5000 feet may be needed.

The main shortwave trough is forecast to exit into New Mexico late
Thursday night, but we will remain under broad upper level
troughing. Friday looks to be quite chilly with only some
occasional peaks of sunshine as some low level moisture will
linger over the area and additional higher level moisture is
expected to spread in from the northwest. Guidance is now a little
more optimistic with a weak follow-on shortwave producing some
light shower activity as early as Friday afternoon focused over
south-central Arizona into the higher terrain. This could bring up
to another tenth of an inch of rain across the Phoenix area to
0.1-0.2" over the higher terrain east of Phoenix. Snow levels will
remain quite low Friday into early Saturday at around 4000-4500
feet, but surface temperatures will be above freezing for most of
Friday. Another 1-2" of snow looks to be possible mainly above
5000 feet Friday night once temperatures fall back to around
freezing.

Upper level ridging and increasing subsidence aloft will gradually
spread over the region from west to east during the daytime hours
Saturday, but it still looks possible for some lingering showers
over the eastern Arizona higher terrain through the afternoon.
Temperatures will warm up modestly on Saturday with highs likely
reaching to around 70 degrees across the western deserts to the
mid 60s in the Phoenix area. The main warming will occur going
into Sunday and Monday as guidance shows H5 heights increasing to
between 577-580dm. Drier air will also move into the region during
this time with sunny skies expected Sunday and partly sunny skies
on Monday. NBM forecast highs show readings topping out near
normal on Sunday and then around 80 degrees across the lower
deserts Monday. An overall dry and quick moving upper level trough
is slated to move through the region Monday night into Tuesday
and this will usher in some cooler air and drop temperatures to a
few degrees below normal for next Tuesday and Wednesday. Ensemble
guidance then mostly favors weak ridging over our region later
next week with dry conditions prevailing and temperatures
gradually warming to slightly above normal.

&&

.AVIATION...Updated at 1220Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Showers are now beginning to exit the Phoenix metro area this
morning, allowing drier conditions to prevail at the terminals.
Lower CIGs will continue to be an issue, however, with a 30-50%
chance of seeing some MVFR CIGs through the rest of the morning.
VFR conditions are likely by midday but will continue to hold onto
CIGs around 5-7 kft through the afternoon. Clouds are expected to
decrease in coverage this evening with FEW-SCT decks aoa 6 kft.
Light winds favoring the SSW this morning will see periods of
variability before switching to the E-SE later this morning. Winds
are expected to make a late switch to the W this evening, while
speeds remain light aob 8 kts.

Southeast California/Southwest Arizona including KIPL and KBLH:
The primary aviation weather concern will be the possibility of
fog this morning at KIPL, however, confidence remains too low to
reflect in the TAF at this time. Will continue to monitor trends
and update the KIPL TAF as needed. Otherwise, light and variable
winds are favored this early this morning before taking on a
southerly component mid morning. West winds take hold at KIPL
later this afternoon with gusts around 20 kts through the evening.
At KBLH, winds will favor the south through the period with gusts
to around 20 kts this afternoon. SCT-BKN clouds aoa 6 kft will
continue throughout the period.

&&

.FIRE WEATHER...
An unsettled weather pattern will continue through at least Friday
with a strong weather system moving through on Thursday.
Lingering showers will be possible across the higher terrain early
today, while breezy southerly winds develop across the western
districts. Windy conditions will then develop areawide by late
Thursday morning as a cold front with a line of showers and
isolated thunderstorms sweeps eastward through the area. Chances
for wetting rains Thursday will mostly be above 70% areawide.
Humidities will remain elevated through the period with MinRHs
generally above 35%. Below normal temperatures will persist into
the coming weekend with additional light rain and snow chances
mainly across south-central and eastern AZ Friday night and
Saturday morning. Drier and warmer conditions are then expected to
prevail Sunday through early next week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory from 8 AM to 10 PM MST Thursday for AZZ530.

     Wind Advisory from 11 AM to 10 PM MST Thursday for AZZ556>558-
     560>563.

     Wind Advisory from 11 AM to 8 PM MST Thursday for AZZ531>533-535-
     536.

     Wind Advisory from 11 AM to 6 PM MST Thursday for AZZ534-537>555-
     559.

CA...Wind Advisory from 8 AM to 10 PM PDT Thursday for CAZ560-561-
     563>570.

     Wind Advisory from 8 PM this evening to 11 AM PDT Friday for
     CAZ562.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Smith
FIRE WEATHER...Kuhlman