Garden Grove, California Weather Forecast Discussion

846
FXUS66 KSGX 202057
AFDSGX
Area Forecast Discussion
National Weather Service San Diego CA
157 PM 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 arrives Thursday. 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...
Low clouds have been rather persistent along the immediate coast
today, but everywhere else has been bright and sunny with a few
cotton ball cumulus over the mountains and desert. It has been
cooler near the coast today with the marine layer reasserting
itself, but warmer inland under sunnier skies and drier air. 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, mostly to the south and east. 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 Tuesday,
adding a little more energy to the system and also concentrating
and deepening the moisture column. That`s when chances of
measurable rain and instability increase, enough for deeper
convection and a small chance of thunderstorms. But this is when
the range of outcomes widens. In a new development, many
ensembles now do not bring the plume directly into our region
Tuesday, but rather a glancing blow as the main plume hits to our
west. The chances and forecast amounts of rainfall have come down
a little for the three days. Finally, the moisture pushes out to
the north on Wednesday, leaving only a slight chance of showers
and thunderstorms in the mountains and desert of San Bernardino
County. 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...
202000Z....Coast/Valleys...Satellite shows low clouds have generally
cleared to just along the coast with bases 700-1000ft MSL. These
clouds will hang for much of the afternoon before pushing back
inland around 01-02z Sun. Bases may lower just a bit to 600-1000ft
MSL with similar inland coverage as was observed this morning. Low
clouds look to clear quicker to the coast on Sunday, closer to 15-
17z. SHRA will begin to move into the region generally after 10z,
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 which could briefly lower visibly. Slight chance for a few
thunderstorms over the waters Monday night into Tuesday evening. 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 Tuesday, peaking Tuesday afternoon.
&&
.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/BEACHES...Zuber

NWS SGX Office Area Forecast Discussion