077
FXUS65 KPSR 221730
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1030 AM MST Fri Nov 22 2024

.Update...Updated 18z Aviation Discussion.

&&

.SYNOPSIS...
High pressure over the region will promote well above normal
temperatures with lower desert highs in the upper 70s to around 80
degrees through Saturday. Pacific moisture aloft will lead to
increasing cloud cover starting Sunday, which will result in warmer
overnight lows. For the first half of next week, temperatures are
expected to gradually fall to near normal under mostly cloudy skies.
Any precipitation chances early next week will be confined to the
higher terrain of Northern Arizona.

&&

.DISCUSSION...
Current mid-lvl wv imagery and 500 mb streamline analysis reveals
a deep cutoff low located over the Pacific NW with a broad plume
of moisture and rainfall overspreading NorCal. Meanwhile, a ridge
of high pressure remains the predominate feature over the Desert
Southwest which will continue to result in warm and dry weather.
500 mb hghts will peak around 583-585 dam today which is around
the 90th percentile of climatology for late November. Thus, highs
are expected to reach upwards of 8-10 degrees above normal across
the lower deserts this afternoon. Expect highs to top out in the
upper 70s across SE California to lower 80s in S/C Arizona. A very
dry airmass remains in place with relative humidity in the teens
and single digits which should result in another cool night across
the area with lows in the 40s to around 50 degrees.

Heading into this weekend, ridging over the Desert Southwest will
begin to flatten and zonal flow aloft will develop as the
aforementioned trof over the Pacific NW begins to deepen and move
on shore. As this occurs, a reinforcing push of Pacific moisture
will arrive over SoCal, bringing soaking rainfall to the West
Coast. Forecast soundings for KPHX and KYUM do show increasing
moisture in the 700-500 mb layer beginning Sunday which would
indicate an uptick in mid to high lvl cloud cover over our region.
However, the boundary layer looks to be far too dry for any
precipitation at this time. If cloud cover becomes thick enough,
temperatures will likely be much closer to normal by Sunday with
highs in the low to mid 70s across the lower deserts.

Ensemble cluster analysis continues to show the deep cutoff low over
the Pac NW transitioning to an open wave and eventually swinging
through the Intermountain West early next week. Currently, the best
lift with this system well remain focused well north of our region,
keeping higher PoPs focused over the Arizona high terrain during the
Tuesday/Wednesday timeframe. We will continue to see periods thick
mid to high level clouds Monday through Wednesday with near to
slightly above normal temperatures persisting.

&&

.AVIATION...Updated at 1830Z.

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

No aviation weather concerns are expected through Saturday
morning under mostly clear skies, with some high cirrus mainly to
the south of the region. Light winds, AOB 5 kt, with extended
periods of variability and even calm conditions will be common.
Expect directions for the Phoenix sites to generally favor a
westerly component later this afternoon into the evening before
switching back out of the typical drainage (E`rly) directions.

&&

.FIRE WEATHER...
High pressure will persist over the region with temperatures
running several degrees above normal through Saturday until
increasing cloud cover brings temperatures closer to normal by
Sunday. 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 above 30% 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...Salerno
AVIATION...Whittock
FIRE WEATHER...Salerno