Area Forecast Discussion
Issued by NWS Phoenix, AZ

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858
FXUS65 KPSR 061710
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1010 AM MST Wed Nov 6 2024

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
An active weather pattern will help keep temperatures in a below to
near normal range through the next 7 days, with generally dry
conditions prevailing. As a low pressure system dives south into the
Desert Southwest, breezy to locally windy conditions are expected
today, particularly along the Lower Colorado River Valley and over
portions of Southeast California. This system will be capable of
producing overall light precipitation amounts for the Eastern
Arizona high terrain through Thursday.

&&

.DISCUSSION...
Satellite imagery and objective analysis depict a potent upper level
low diving south southwest at this hour, currently centered over
eastern Utah. This is the system that will be responsible for
ushering a colder air mass into the region over the day today, as
well as bringing widespread breezy to locally windy conditions. The
strongest winds today will be focused over the Lower Colorado River
Valley and portions of SE CA, with northerly gusts to between 35-45
mph. This is supported by ensemble and Hi-Res guidance, which
advertises 850 mb flow upwards of 30-35 kt, peaking sometime this
morning over the western CWA. As such, A Wind Advisory will be in
effect through this evening for locations along the Lower Colorado
River Valley and zones just to the west. Another Wind Advisory
segment has been added to capture the Yuma Area and Southeastern
Imperial County including Glamis, though Advisory-level (40+ mph)
gusts are only expected to pick up there after sunrise and last into
early this afternoon as the pressure gradient slackens over the
course of the day. Moisture availability with this system will be
lacking (South-Central AZ PWATs peaking around 0.4-0.5") resulting
in near zero rain chances across lower elevation areas. However, the
dynamics of this system, along with orographic assistance, may be
enough to squeeze out some showers over the eastern Arizona high
terrain through Thursday, resulting in overall light accumulations.

Another aspect of this system will be the much colder air parked
over the region, as the upper low settles over eastern AZ later
today and lingers through Thursday. At the center of the low, NAEFs
and ENS mean 850-700 mb temperatures are below the 1st percentile of
climatology. As the position of the low has trended slightly further
south in the latest model runs, the most recent NBM now advertises
that some of the higher elevation desert communities east of Phoenix
will have a decent chance at seeing freezing temperatures (overnight
lows in the lower 30s). A Freeze Warning has been issued for the
high terrain east of Phoenix including the communities of
Globe/Miami and San Carlos, valid midnight tonight through 9 AM MST
Thursday morning. Lower desert highs through the end of the work
week will range mostly in the 60s to lower 70s, with Thursday
shaping up to be the coolest day.

By Friday, the upper low will have shifted east of Arizona, and
heights aloft will begin to rebound to near average for this time of
year. Weak ridging is still depicted by ensembles over this weekend,
with potentially a weak disturbance passing over the area that will
act to keep heights aloft from increasing much above average. As a
result of this evolution, a gradual warming trend should carry us
through the weekend, with near normal highs in the upper 70s to
lower 80s by Sunday and into early next week. Beyond Monday,
guidance begins to diverge, with another trough expected to enter
the western US. Cluster analysis reveals considerable uncertainty
with respect to how progressive this next trough will be and how
much it will deepen once it moves inland. This is reflected in the
NBM temperature spread, with IQRs of around 10F Tuesday onward.
Either way, the somewhat active pattern continues into next week,
and PoPs for the system next week are currently quite low (no more
than 20%, and only over the high terrain of the eastern CWA).

&&

.AVIATION...Updated at 1710Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
An extended period of northerly cross runway winds along with
occasional gustiness will be the primary weather issues through
Thursday morning as mid/high level cigs clear the region. Confidence
is good that NE winds will prevail across the metro through the
afternoon with occasional gusts up to 20 kt. There will be a
tendency for wind directions to attempt to become more NW after
sunset, however a period of 030v330 may be common until the early
morning hours. Directional variability and multiple subtle wind
shifts may impact operations later Thursday morning.


Southeast California/Southwest Arizona including KIPL and KBLH:
Very gusty north winds with areas of lofted dust will be the
greatest weather concerns through Thursday morning under mostly
clear skies. North gusts will increase through the afternoon with
good confidence of peaking in a 25-40kt range. While there may be
some sfc visibility restrictions, lofted dust and late afternoon
slantwise vsby issues seem more likely. Otherwise, gusts should
relax somewhat after sunset with more modest gustiness
returning Thursday afternoon.

&&

.FIRE WEATHER...
Well below normal temperatures will prevail through the end of the
work week. A mostly dry weather system will dive south into the
Desert Southwest today and linger through Thursday. This system will
bring breezy to locally windy conditions across the western
districts for much of today, with wind gusts along the Lower
Colorado River Valley and portions of Southeast California to
between 35-45 mph. Light shower activity will be possible across the
eastern Arizona higher terrain through Thursday afternoon, but CWR
for the high terrain of the eastern districts is 5% or less. MinRHs
today will fall in the upper single digits up to around 15% and will
mainly fall into the teens on Thursday across the lower deserts,
with readings closer to 20-30% over higher terrain areas each day.
For late this week into the weekend, dry conditions will persist
with weak high pressure eventually pushing temperatures from below
normal into the normal range over the weekend.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory until 8 PM MST this evening for AZZ530.

     Wind Advisory until 2 PM MST this afternoon for AZZ532.

     Freeze Warning from midnight tonight to 9 AM MST Thursday for
     AZZ557-558-560-562.

CA...Wind Advisory until 7 PM PST this evening for CAZ564-569-570.

     Wind Advisory until 1 PM PST this afternoon for CAZ565.

     Freeze Warning from 11 PM this evening to 8 AM PST Thursday for
     CAZ560.

&&

$$

DISCUSSION...Whittock
AVIATION...18
FIRE WEATHER...Whittock