579
FXUS66 KSGX 222109
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
209 PM PDT Thu May 22 2025

.SYNOPSIS...
High pressure aloft will weaken with a low pressure system moving
inland through California on Friday night. High temperatures will
cool from around 10 degrees above average today to within a few
degrees of average on Saturday. Sunday will be around 5 degrees
warmer, then gradual cooling to around average for next Wednesday.
There will periods of stronger and gusty southwest to west winds
for the mountains and deserts during the afternoon and evening
for today and Thursday with the stronger gusts today to 30 to 40
mph and on Thursday to 35 to 45 mph. The marine layer will deepen
into Saturday with night and morning coastal low clouds spreading
farther inland into the valleys each morning through Saturday.
Coastal low clouds won`t extend as far into the valleys on Sunday.
For the early and middle part of next week, the marine layer will
be deepen with night and morning coastal low clouds extending
inland across much of the inland valleys with slower or more
limited afternoon clearing near the coast.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Tonight through tomorrow...

Most of the low clouds have scattered out completely, with only a
few areas of broken skies right along the immediate coast of
southern Orange County and northern San Diego County. There could
also be some patchy areas of fog again, although likely a little
further inland due to ceilings rising a little more. As clouds
thicken up due to an approaching trough, there could be some areas
of drizzle possible, especially for the foothills and west-facing
slopes. Winds will continue to increase and become gust for some of
the deserts and mountains, with some more localized areas within
Banning Pass and other locations which are more prone to strong
winds to occasionally reach Wind Advisory criteria. These winds will
begin to decouple and weaken going into the later hours overnight.

For tomorrow, there will be some areas of fog during the early
morning hours for portions of the inland valleys, and likely a
little further eastward. There could be some patchy drizzle
possible, likely more for the inland areas and foothills, although
not highest enough confidence to put this into the forecast grids.
As a shortwave trough begins to move in over the region, the
tightening of the pressure gradient is going to allow for winds to
increase for the lower elevations of the deserts, and approaching
Wind Advisory criteria. There could also be some areas of blowing
dust, especially within the first couple of hours after winds
increase within the Coachella Valley. Due to this, and winds being
strongest within this location, a Wind Advisory has been issued for
the San Gorgonio Pass near Banning from 5 PM Friday through 3 AM
Saturday.

This weekend through mid next week...

Winds will continue to diminish going into the early hours on Sunday
as the trough continues to pull away from the region. There will be
an overall area of troughing over the northwestern region, and
possibly a weak upper level low transitioning over California during
the early part of next week, which could help to reinforce some
cooler temperatures and allow for a slight chance of precipitation.
Otherwise, generally it will remain cooler and more moist with a
persistent onshore flow in place through the middle of next week.

&&

.AVIATION...
222045Z...Coast...This morning`s low clouds have cleared but remain
along most beaches and just offshore this afternoon. These clouds
will push back ashore as early as 02-03z this evening with more
inland extent and slightly higher bases than this morning. Expecting
CIGs near 800-1400ft MSL with about 15-20 mile of inland extent. 40%
chance CIGs reach KONT and 20% at KSBD. Better visibility along the
coasts and western valleys, but VIS restrictions focused more within
inland higher terrain. Clearing Friday morning expected at a similar
time as this morning, around 17-18z.

Elsewhere...Clear with unrestricted VIS through Friday morning. West-
northwest wind gusts locally 25-35 kts this afternoon within
mountain passes and along desert mountain slopes strengthen to 35-45
kts Friday afternoon.

&&

.MARINE...
Winds gusting near 20 kts near San Clemente Island on Friday
afternoon, otherwise, no hazardous marine conditions are expected
through Tuesday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 5 PM Friday to 3 AM PDT Saturday for San
     Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...Stewey
AVIATION/MARINE...Munyan