Capistrano Beach, California Weather Forecast Discussion

577
FXUS66 KSGX 201603
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
903 AM PDT Sat Sep 20 2025
.SYNOPSIS...
Warm and dry today with some coastal clouds. Tropical moisture
returns Sunday with scattered light showers, most widespread
across the mountains and San Diego County. Small chances of
showers continue Monday, increasing for Tuesday and possibly into
Wednesday, along with a slight chance of thunderstorms. Drier
weather appears to arrive Thursday and Friday. Temperatures will
be mild this coming week, with decreasing coastal low clouds.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Coastal low clouds made a valiant return overnight, except in
northern Orange County. Look for lots of sunshine today for all
areas after the coast clears. There is a slim layer of residual
mid level moisture today, but that should only bring some cumulus
clouds over the mountains this afternoon. It will be a little
warmer today than it was yesterday. An upper level low pressure
trough drops south off the CA coast and camps out just west of
SoCal in the next few days. It draws a lot of mid and upper level
moisture into our region late tonight and Sunday from a tropical
disturbance southwest of Cabo San Lucas, not a tropical cyclone.
The moisture is rather high, staying mostly above 12,000 feet, but
enough to warrant isolated to scattered showers, but also
sprinkles and virga. The moisture plume thins out a little on
Monday, for a lesser but nonzero chance of showers. Meanwhile,
the destabilizing environment will wreak havoc on our marine
inversion so that coastal low clouds incrementally decrease each
night and morning. The upper low seems to cut off and deepen,
adding a little more energy to the system and also concentrating
and deepening the moisture column for Tuesday. That`s when
chances of measurable rain and instability increase, enough for
deeper convection and a small chance of thunderstorms. This is
when the range of outcomes widens. Some ensemble members rotate
the low northward late Tuesday, taking the moisture with it, so
that Wednesday looks dry. Other ensembles show a slower
progression such that SoCal remains within the more potent
moisture plume both Tuesday and Wednesday. Still other solutions
keep the Wednesday moisture mostly to our west, with SoCal on the
fringes. Still, a very slight chance of precipitation Wednesday.
Greater certainty actually comes later next week as most solutions
weaken the cutoff low over the west, north of SoCal, to bring dry
weather. With a weak trough over the West, high temperatures will
continue mild, a few degrees below average, through the end of
the week. In the absence of the tropical moisture, the marine
layer should be able to tepidly rebound and rebuild and bring
more coastal clouds.
&&
.AVIATION...
201600Z....Coast/Valleys...Low clouds based 400-1000ft MSL
sufficiently pushed 5-10 miles into San Diego County this morning
with patchy low clouds in Orange County. VIS remains very low, 1-5SM
within 10 miles of the coastline, locally lower to 1/2SM in some
valleys and at coastal terrain. Bases will slowly rise and clear to
the water by 18z, with stratus potentially prevailing at the beaches
into the afternoon. Low clouds with bases 600-1000ft MSL develop and
push inland again tonight after 01-02z Sun through 10z, with similar
inland coverage. Low clouds look to clear quicker on Sunday, closer
to 15-17z. SHRA will begin to move into the region generally after
10z Sun, with more widespread SHRA after 15z. Locally lower VIS and
CIGs with any shower.
.Mountains/Deserts...VFR conditions and mostly clear skies through
early Sunday. Mid and high level clouds AOA 10,000 ft MSL enter the
region this evening. SHRA move into the region generally after 15z,
with brief lowering of VIS and CIGs with any shower.
&&
.MARINE...Rain showers possible for much of the day Sunday and again
Monday afternoon which could briefly lower visibly. Slight chance
for a few thunderstorms over the waters overnight Monday into
Tuesday afternoon. Any storm could briefly produce lightning, gusty
erratic winds, and choppy seas. Otherwise, no additional hazardous
marine conditions are expected through Wednesday.
&&
.Beaches...
Thunderstorm chances return early Tuesday, peaking early Tuesday
afternoon, and may prevail into early Wednesday.
&&
.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...MM
AVIATION/MARINE...Zuber

NWS SGX Office Area Forecast Discussion