114
FXUS65 KPSR 062310
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Mon Jan 6 2025

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
A weather system will move through the region tomorrow into
Wednesday bringing cooler temperatures, breezy to locally windy
conditions, and precipitation chances. The best precipitation
chances will be in the Arizona higher terrain areas with little to
no rainfall accumulation across the lower deserts. Temperatures will
cool to near and slightly below normal levels through the weekend.

&&

.DISCUSSION...
A highly amplified ridge of high pressure situated over the eastern
Pacific, with positive height anomalies extending into western
Canada, continues to provide dry, tranquil weather conditions across
the Desert Southwest. Temperatures will once again be slightly above
seasonal normals today as afternoon highs top out in the upper 60 to
low 70s under mostly clear skies. This will change starting tomorrow
as an unsettled pattern sets up over the region.

Early afternoon satellite WV imagery showed a shortwave trough
digging southward across the Great Basin along the eastern periphery
of the amplified ridge. This trough will continue to dive southward
into Arizona going into Tuesday while deepening into a closed low.
As this system pushes into our area while strengthening, gradients
will increase and lead to increasing winds across the western
deserts starting tomorrow morning. Strong, gusty winds will
initially be focused along and west of the Lower Colorado River
Valley tomorrow where gusts could exceed 40 mph at times. Thus, a
Wind Advisory is in effect for much of southeast California starting
tomorrow morning and continuing into Wednesday morning. As the
closed digs further southward into northern Mexico with a
strengthening surface low, gradients will tighten across Arizona
heading into Wednesday with strong, gusty winds expanding across the
region. Gusts across the region for Wednesday are expected to climb
upwards of 20-35 mph with some gusts in excess of 40 mph,
particularly across the high terrain east of Phoenix and areas along
and west of the Lower Colorado River Valley. Given the magnitude of
the winds forecast and dry conditions in place, blowing dust will be
possible in dust prone areas, which can reduce visibilities and make
travel hazardous.

Precipitation chances will increase Tuesday evening into Wednesday,
however, moisture with this system will be limited given the inland
trajectory and thus limit any precipitation we see. Ensembles show
PWAT values only increasing to around 0.4-0.5" with much of this
moisture residing in the 700-400 mb layer according to the latest
forecast soundings. The latest 12Z HREF show isolated virga/light
showers popping up Tuesday evening with the better precipitation
residing across the Arizona high terrain. Locally, PoPs are highest
across the southern Gila County high terrain with lower chances
across the lower deserts. Little to no rainfall accumulation is
forecast across the lower deserts with WPC QPF focusing amounts
upwards of 0.10-0.25" across the high terrain east of Phoenix. Snow
showers will be possible late Tuesday into early Wednesday across
southern Gila County as snow levels fall to around 3,000 feet, but
any accumulation is expected to remain light.

&&

.PREVIOUS DISCUSSION...
For the latter half of the workweek, global ensembles continue to
show the closed low moving through northern Mexico before opening up
and moving into the Plains and Midwest. Ensemble members also show a
shortwave trough moving down into our region on the backside of the
low on Thursday. While precipitation chances will come to an end by
Wednesday night, this shortwave trough will help keep temperatures
near or slightly below seasonal levels for the end of the workweek.
With the NBM deterministic model showing afternoon high temperatures
in the mid 60s to near 70 degrees across the lower deserts and in
the 50s for the higher terrain areas. Mostly clear skies and light
winds will result in chilly overnight and early morning low
temperatures with temperatures forecasted to be in the mid 30s to
low 40s across the lower deserts. The more rural and typical cold
spots, like Wickenburg and Casa Grande, are forecasted to see
temperatures dip to near freezing or even into the upper 20s. These
cooler temperatures are forecasted to last for several days and
freeze products may be needed for these locations. The
aforementioned shortwave could also lead to some more breezy
conditions Thursday afternoon, mainly in southeastern California.
Global ensemble models show another trough moving through our region
late this weekend and into early next week, which would help to keep
our temperatures near seasonal levels heading into next week.

&&

.AVIATION...Updated at 2310Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
A period of northerly cross runway winds with the potential for
highly variable directions Tuesday afternoon will be the greatest
weather issue this TAF period. Confidence is good that light west
winds will revert to an easterly component by mid evening, then
maintain a E/NE direction into Tuesday afternoon. In attempting to
switch to a westerly direction, a period of 030v330 directions will
be possible late afternoon into early evening with speeds increasing
near (or above) 10kt. Concurrently, confidence is excellent that 10K
ft AGL cigs will develop with some localized virga during the
afternoon. While a much lower probability, erratic winds are
possible with any concentrated areas of virga before wind directions
settle back into a NE direction Tuesday evening.


Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty north winds Tuesday afternoon and evening will be the primary
weather issue this TAF period as cigs 10K ft AGL develop over the
region. Confidence is very good that light winds this evening will
steadily become northerly overnight, then increase in speed with
stronger gusts by late morning. Gusts should be most pronounced at
KBLH above 30kt at times. This may result in some MVFR BLDU during
the afternoon, however confidence in any given time range is too low
to include in this TAF package.

&&

.FIRE WEATHER...
Dry conditions with slightly above normal temperatures and light
winds will continue today. MinRHs will be in the teens today before
increasing to 20-30% across the majority of the area on Tuesday and
Wednesday. A weather system moving through the region Tuesday
through Wednesday will lead to breezy to locally windy conditions
along with some light precipitation chances. Highest winds are
expected along the Lower CO River Valley and highest precipitation
chances are expected in the higher terrain to the east of Phoenix.
This system will also knock temperatures down to near to slightly
below normal levels.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory from 8 AM Tuesday to 11 AM MST Wednesday for
     AZZ530.

CA...Wind Advisory from 7 AM Tuesday to 10 AM PST Wednesday for
     CAZ560-561-564-565-568>570.

&&

$$

DISCUSSION...Smith
PREVIOUS DISCUSSION...Berislavich
AVIATION...18
FIRE WEATHER...Berislavich