322
FXUS65 KPSR 212302
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
400 PM MST Thu Nov 21 2024

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
High pressure over the region will bring slightly above normal
temperatures into the weekend with lower desert highs in the upper
70s to around 80 degrees through Saturday. Dry conditions will
continue through at least the weekend with skies eventually becoming
fairly cloudy starting Sunday. For the first half of next week,
temperatures are expected to be near to slightly above normal under
mostly cloudy skies, while rain chances are currently forecast to
remain less than 10% for most places.

&&

.DISCUSSION...
The latest visible and IR satellite imagery show a well-defined
upper level low spinning off the Pacific Northwest coast while an
atmospheric river brings excessive rainfall to northern California.
Across the Desert Southwest, an upper level ridge continues to
dominate our weather with dry, tranquil conditions persisting.
Today, 500 mb heights will peak upwards of 586-588 dm, which is
above the 90th percentile for this time of year. As a result,
temperatures will warm upwards of 4-9 degrees above seasonal normals
as high temperatures across the lower deserts top out in the upper
70s to low 80s today and tomorrow. Cool overnight lows will remain
in the 40s to around 50 degrees with a few colder spots dipping into
the 30s over the next couple of mornings. Above normal temperatures
will persist into the weekend, while skies are forecast to remain
mostly clear through Saturday with some passing cirrus at times.

Ensemble guidance show good agreement that heights will gradually
lower through the weekend into the beginning of next week as the
current eastern Pacific longwave troughing pushes further south and
east. As this occurs, the ongoing AR will push toward the south
while weakening before a second weaker AR pushes into southern
California and the southwest CONUS for the start of next week. This
will usher in mid and upper level moisture and promote expansive
cloud cover over our area for the start of the new week. Despite the
increase in moisture with ensemble PWAT anomalies climbing upwards
of 150-200%, the lack of boundary layer moisture and forcing
mechanisms will limit rain chances across the region with NBM PoPs
remaining below 10% early next week. Ensemble cluster analysis
indicate the potential for a shortwave trough to propagate
southeastward into the Four Corners region heading into the middle
part of next week. Currently, the best dynamics with this system are
favored to remain to our north with much higher PoPs focused over
the Arizona high terrain during the Tuesday/Wednesday timeframe. For
now, the most likely outcome for our area will be to have overall
cloudy skies starting Sunday, with near to slightly above normal
temperatures persisting into the middle part of next week as
forecast highs top out in the mid 70s. Overnight lows will trend
upward into the mid 40 to mid 50s starting this weekend and
continuing into early next due to the thick cloud cover.

&&

.AVIATION...Updated at 2300Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

No weather issues will exist through Friday evening under a few
passing high cirrus decks. Trends in winds will be nearly identical
to the past 24 hours with speeds under 8kt and extended periods of
calm conditions.

&&

.FIRE WEATHER...
High pressure will persist across the region into the weekend with
temperatures running a few degrees above normal. Dry conditions are
expected through at least Saturday with MinRHs around 10% across the
lower deserts to 15% in higher terrain areas before humidities
increase Sunday into early next week under fairly cloudy skies. The
weather pattern will continue to support overall light winds with
only some periodic light breezes mainly during the morning hours and
focused along ridgetops.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.

&&

$$

DISCUSSION...Smith
AVIATION...18
FIRE WEATHER...Kuhlman