946
FXUS66 KSGX 141638
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
938 AM PDT Sat Sep 14 2024

.SYNOPSIS...
A weak weather disturbance will move through Southern California
and keep temperatures slightly below averages. The marine layer
will remain deep providing cool conditions for the valley and
coast. A stronger weather system is expected to arrive Sunday
night and Monday and bring gusty winds and unseasonably cool air.
Areas of light precipitation are also expected on Monday, west of
the main mountains. A slight warming trends will start on Tuesday
but another cool weather disturbance will enter southern
California for mid week.

&&

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

Deep marine layer continues, up to 3500 feet MSL and as high as
4000 feet. A weak short wave trough will arrive today increasing
southwest flow ahead of it and sustaining the deep marine air
mass. Temperatures today are expected to be several degrees below
average. Very dry air does exist still above 6000 feet, affecting
the mountains. Dewpoint temps as low as teens above 7000 feet.

An unseasonably strong upper trough will enter Socal during Sunday
night Monday. The winds will be gusty and much stronger but due to
the deep marine layer and even colder air mass the humidity will
be considerably high and widespread light rainfall and even
scattered showers with the trough passage on Monday. Wind gusts of
40 to 60 mph for wind prone mountains passes and ridges. 700 mb
southwest wind flow is forecast to be 30 to 40 knots with
temperatures down to 2C for San Gabriel mountains. Mixed out
marine layer for Tuesday and Wednesday along with a modified
warming air mass and light winds.

The pattern looks to repeat itself for mid week, with a similar
strong cold front crossing Socal by Thursday. This would also
bring some precipitation in addition to the deep marine layer. By
Friday this would shift to slight offshore flow and drying. This
system has potential to close off and dig with time.

&&

.AVIATION...
141600Z...Coasts/Valleys...Satellite shows that log clouds pushed 30
miles inland this morning, with CIGs at all valley and coastal
sites. Bases around 2000-2500ft MSL with tops to 3200ft MSL. Ongoing
FU from nearby fires will continue to reduce VIS, with the marine
layer trapping FU near KSBD where VIS is currently 3SM. Similar to
what was observed on Friday, clearing will occur from southeast to
northwest through the morning, with most sites clearing by 17-18z.
Hazy conditions may continue to be observed through the afternoon
due to the FU, especially for the valleys. There remains some
uncertainty if complete clearing will occur along the coast or if
some sites (primarily KSAN) will have a CIG through the afternoon.
If clearing manages to happen, marine layer will build back in again
this evening, around 00-02z Sunday, with similar bases and tops.

Mountains/Deserts...Local VIS restrictions will continue through Sat
evening due to FU over the San Bernardino County Mountains near the
Line Fire and Bridge Fire and the Santa Ana Mountains near the
Airport Fire. Otherwise, mostly clear skies with unrestricted VIS
prevails through Sunday morning.

&&

.MARINE...
Stronger winds will occur in the outer coastal waters Monday and
Monday night with gusts 20-25 knots likely from the W/NW. Otherwise,
no hazardous marine conditions are expected through Wednesday.

&&

.FIRE WEATHER...Ongoing wildfires, Line, Airport and Bridge
continue to be the main weather support. Increased wind and drier
air above 6000 feet will be main concern for Sunday night and
Monday otherwise deep marine layer and cooler air mass is helping
with containment. Fuel moistures that were record low are
recovering quickly expect less on high terrain.

&&

.CLIMATE...The upper troughs on Monday and Thursday are
unseasonably cool in addition to some precipitation. This is
after a record heat wave we experienced the first week of
September.

&&

.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/FIRE WEATHER...Tardy
AVIATION/MARINE...Zuber