098
FXUS65 KPSR 081845
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1145 AM MST Wed Jan 8 2025

.UPDATE...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
A cutoff low pressure system will continue to progress through the
region today, resulting in widespread breezy to windy conditions and
widely scattered showers/virga. Much cooler temperatures will follow
in the wake of this system with highs remaining below normal through
this weekend. Morning lows will also be significantly colder with
some desert locales expected to reach the freezing mark beginning
Thursday morning.

&&

.DISCUSSION...
Latest mid-lvl wv imagery and 500 mb streamline analysis reveals a
cutoff low situated over the Baja Del Norte. Our forecast region
is located just north of this feature in the deformation axis/band
which has set up over southcentral AZ. Unfortunately this system
is currently moisture starved and precipitation has been hard to
come by. Despite adequate lift and divergence aloft, the lack of
low lvl moisture has been a limiting factor in precipitation
reaching the ground. The main impacts with this system so far has
been winds. A strong mid tropospheric jet coupled with a tight
pressure gradient near the sfc has resulted in wind gusts in the
30- 50 mph range across southeast CA and portions of southcentral
AZ. Gusty winds will persist today, especially after sunrise as
strong winds aloft mix down to the sfc. A Wind Advisory remains in
effect until 21Z (2PM CST) for portions of southeast CA, the
Lower Colorado River Valley, in addition to the foothills of E
Maricopa and N Pinal Counties where the strongest gusts will
reside. The most notable impacts with these winds will be
difficult driving conditions for high-profile vehicles and
localized dense blowing dust channels. The I-10 corridor in
southeast CA and Pinal County, AZ will have the greatest risk
for these impacts through this afternoon.

Heading into tonight, the center of the upper low will continue to
weaken and push southward into N MX. As this occurs, precipitation
chances will come to an end and wind speeds will subside region-
wide. Dry air will begin to filter into the region from the NW as
the system pulls away from our area. This dry air coupled with
clearing skies will allow temperatures to plummet on Thursday
morning. Most lower desert communities will see morning lows in
the mid 30s to low 40s early Thursday, however some locations will
see lows dip below freezing. Therefore, the previous Freeze Watch
has been upgraded to a Freeze Warning for Globe/Miami, San
Carlos, Superior, Wickenburg, and lower elevations of N Pinal
County where temperatures are expected to fall into the upper 20s
to low 30s. A reinforcing shot of cool air will arrive Thursday
afternoon as a secondary shortwave trough dives south into far E
AZ. The trajectory of this trough looks to remain east of the
region which will keep any precipitation chances well off to the
east. The 700-500 mb hght gradient will tighten on the back side
of this system, leading to another bout of gusty winds primarily
across SE California and SW Arizona where gusts up to 25-35 mph
will be possible. Highs will be much closer to seasonal norms
Thursday afternoon in the low to mid 60s across the lower deserts
with 50s in the higher terrain.

Ensemble clusters are in good agreement that negative hght anomalies
and overall troughing will linger into this weekend which means we
will continue to see near to slightly below normal temperatures from
Friday through at least Monday. High temperatures should remain in
the low to mid 60s across the lower deserts (normal high for Phoenix
is 67 degrees). We will also likely continue to see cold mornings
with lows settling into the 30s and 40s. There is currently a
greater than 70% chance for locations that are currently in the
Freeze Warning to see a recurrence of freezing temperatures each
morning from Friday through Monday. The current Freeze Warning is
in effect through Friday morning, but will likely need to be
extended into this weekend. The coldest morning according to the
NBM looks to be Sunday where lows could even fall into the mid to
upper 30s in the Phoenix Metro. Other than the cooler than normal
temperatures, expect dry conditions to persist into early next week.

&&

.AVIATION...Updated at 1845Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Gusty E/NE winds will be the main weather concern through this
afternoon, under 10-15 kft AGL CIGS. Confidence is excellent that
stronger, more widespread gusts will continue over the entire
metro with mixing yielding frequent 25-35 kt gusts into mid/late
afternoon before relaxing considerably by sunset. Skies will clear
this evening, and winds will either go VRB overnight or establish
their typical E`rly drainage directions.

Southeast California/Southwest Arizona including KIPL and KBLH:
Strong, gusty north winds through this afternoon will be the
primary aviation concern during the TAF period. Strong wind gusts
30-40 kt (and occasionally higher) will affect KBLH into the
afternoon with lesser speeds (gusts to 25-30 kt) at KIPL. Periods
of BLDU and lofted dust will be likely around KBLH with brief
periods of MVFR vsby restrictions. Visibility impacts at KIPL
should be minimal though lofted dust will be possible affecting
slantwise vsby. Current SCT-BKN coverage will become SKC by this
evening and through the remainder of the period.

&&

.FIRE WEATHER...
A low pressure system will continue to progress through the
region today, resulting in breezy to locally windy conditions.
Easterly winds will be strongest mid-morning today with gusts
ranging from 40-50 mph across southeast CA and foothills of
E Maricopa and N Pinal Counties. Elsewhere, gusts ranging from
20-35 mph can be expected through this afternoon before gradually
diminishing around sunset. Light precipitation will be possible
across south-central AZ today, although little to no measurable
accumulations are anticipated. Relative humidity will bottom out
between 20-35% across the eastern districts and as low as 15-25%
in the western districts this afternoon. Overnight recovery will
range from poor along and west of the Colorado River to good
across south-central AZ. A drying trend is expected through the
remainder of this week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory until 2 PM MST this afternoon for AZZ530-541-542-
     545-547-549-551>553-555-557-558-561-562.

     Blowing Dust Advisory until 2 PM MST this afternoon for AZZ551-
     553-555.

     Freeze Warning from midnight tonight to 9 AM MST Thursday for
     AZZ534-552-553-556-560>562.

     Freeze Warning from midnight Thursday night to 9 AM MST Friday
     for AZZ534-552-553-556-560>562.

CA...Wind Advisory until 1 PM PST this afternoon for CAZ560-561-
     563>565-567>570.

&&

$$

DISCUSSION...Salerno
AVIATION...Whittock/Ryan
FIRE WEATHER...Salerno