835
FXUS65 KPSR 062208
AFDPSR

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

.SYNOPSIS...
Dry and tranquil weather conditions continue today before an
unsettled weather pattern prevails tomorrow. A weather system
will move through the region Tuesday 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 to slightly below normal and are expected to continue 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 1817Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

A low pressure system currently centered over the Great Basin will
lead to windy conditions, increased cloudiness, and a chance of
light showers starting Tuesday evening. But, there is only about
a 10% chance of ceilings dipping below 6kft AGL. Chances of
visibility dropping below 6SM are even less than that. Before
then, Cirrus will continue thinning out early in the TAF period
and surface winds will have a somewhat slow onset of light (AOB
7kts) upvalley/westerly directions (mainly after 21Z) before light
downvalley/easterly winds slowly develop after 02Z.

Southeast California/Southwest Arizona including KIPL and KBLH:

A low pressure system currently centered over the Great Basin will
lead to windy conditions from the north (gusts 25-35kt),
increased cloudiness, and a slight chance of light showers
starting Tuesday morning. But, there is less than a 10% chance of
ceilings dipping below 6kft AGL. Chances of visibility dropping
below 6SM are a little better due to blowing dust but too low to
reflect in the TAFs (better chances at KBLH than KIPL). Before
then, skies will be mostly clear and winds will be light (AOB
8kts). Conditions at KBLH may approach LLWS criteria for a few
hours prior to about 17Z but probability too low at this time to
reflect in the TAF.

&&

.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...AJ
FIRE WEATHER...Berislavich