691
FXUS66 KSGX 192032
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
132 PM PDT Sun Oct 19 2025

.SYNOPSIS...
Weak offshore flow will continue with mostly light winds today and
easterly breezes in the foothills and coastal mtn slopes for
Monday and Tuesday. Near to slightly above average temperatures
expected through Tuesday before below average conditions return
for the middle of the week. Warmer for Friday then cooler again
for next weekend. Patches of marine layer low clouds and fog this
morning, with the potential for areas of dense fog. Low cloud
coverage will become more widespread over the next several days.
Areas of drizzle possible Wednesday for lower elevations west of
the mountains.

&&

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

Patches of low clouds and fog over the coastal waters this
afternoon, moving towards the coast. Low clouds and fog could move
onshore tonight but likely will not spread inland beyond the
coastal areas. Sfc pressure gradients are still weakly offshore in
some locations but a sea breeze has developed and the favored
locations are reporting wind gusts to 20 mph in the last hour.
Current temperatures are within a few degrees of what they were at
this time yesterday...most inland locations are a few degrees
warmer and most coastal locations are a few degrees cooler. High
temperatures today will be near or a few degrees warmer than
seasonal averages.

From previous discussion...
Weak high pressure aloft will persist over the region early this
week but will slowly shift north and east by late Tuesday as a
closed upper low about 600 miles southwest of San Diego moves
toward SoCal. The high pressure will keep temperatures a little
above seasonal averages through Tuesday. Weak offshore pressure
gradients will persist into Tuesday but offshore winds will be
relatively weak and mostly restricted to the coastal slopes of the
mountains and locally into the foothills. The offshore gradients
will likely limit marine layer low cloud and fog coverage. Any low
clouds and fog that do develop will most likely occur over the
coastal waters and near the coast with areas of dense fog
possible.

The closed upper low to the southwest will reach SoCal by
Wednesday, moving northeast and accelerating as another cold
trough begins to move inland to the north over WA/OR. The passage
of this low will bring an increase in cloud cover as the marine
layer deepens, and cooler, locally breezy conditions. Onshore
flow will strengthen and locally gusty winds will develop in the
favored locations of the mtns and deserts. By Wednesday, high
temperatures for inland locations are expected to be 7 to 12
degrees below seasonal averages, with some mountain locations
seeing highs 15 to 20 degrees below average. Rain chances
associated with this system continue to look marginal as most of
the available moisture will be confined to the marine layer.
Chances of measurable rainfall occurring remain less than 10
percent, with the best chances for any accumulating rain on the
coastal mountain slopes. Areas of patchy drizzle are possible west
of the mountains on Wednesday, especially with the increase in
onshore flow and rapid deepening of the marine layer.

As the low moves east on Thursday...a weak, transient ridge will move
in from the west. This ridge will bring a brief period of warming,
weak offshore flow, and a shallower marine layer for Friday.
Marine layer low clouds will be reduced and daytime high
temperatures will be near or a little above seasonal averages.

For next weekend...a deep trough of low pressure from the Gulf of
Alaska will move inland over the western US. Currently, most of
the ensemble members keeps the parent low off the coast of the
Pacific Northwest through next Saturday, which would keep us dry
through then. By next Sunday, most ensemble guidance has the
trough moving inland, although there remains some differences in
timing and amplitude of the trough. There is fairly good consensus
that the track of the low will be more inland and well to the
north, setting up a pattern of high-zonal flow over CA. This
pattern and a lack of deep-layer moisture makes it less favorable
for significant precipitation to occur. There are still some
ensemble members showing that light rain is possible, but more
than likely the main impact from this system for SoCal will be a
strengthening of westerly winds over the mountains and into the
deserts. This trough will also bring a cooling trend with daytime
high temperatures once again below seasonal averages for next
weekend.

&&

.AVIATION...
192000Z....Coasts...Clouds/FG has generally cleared but a few stray
patches of very low marine clouds (based 200-400 ft MSL) remain over
the waters. Low clouds and fog will develop along the coast
beginning around 06z Monday, with around a 55% chance for a CIG at
KSAN for at least 1 hour, a 25% chance at KCRQ, and a 40% chance at
KSNA. Bases will be around 400-900ft MSL, clearing by around 15-16z
Monday.

Valleys/Mountains/Deserts...VFR conditions continue through Monday.

&&

.MARINE...
Patchy fog with visibilities under 1SM will be possible Monday
morning. Otherwise, no hazardous marine conditions are expected
through Thursday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE...Zuber

NWS Tucson (SGX) Office