082
FXUS66 KSGX 092057
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
157 PM PDT Thu Oct 9 2025

.SYNOPSIS...
A low pressure system off the West Coast will draw moisture from
Tropical Storm Priscilla northward into the area for today through
Saturday morning, with chances for showers and a chance for
thunderstorms at times. Cooler with drying and a return of the
marine layer for Saturday through Monday. For Tuesday and Wednesday
of next week, a low pressure system moving southward along the West
Coast will bring a chance of showers along with stronger westerly
winds.

&&

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

Today through tomorrow...

Priscilla has been weakening all morning, and the mid to upper level
moisture associated with this has been streaming up over the region,
and has allowed for some showers and a few very high-based embedded
thunderstorms to impact some of the areas, including Palm Springs
and Ontario. Training storms over the vicinity of Ontario has also
so allowed for measurable amounts up to around a tenth of an inch
for areas near Running Springs. This will continue to be possible
for more training storms for portions of the Inland Empire, and
possibly over some of the lower desert later this evening. The
moisture plume appears as if it is going to be located mostly over
the southeastern half of the CWA by later this evening. Given the
upper level difluence over the region, as there is a trough
located to the northwest, and this could allow for enough
instability to initiate some convection by later this afternoon
over the mountains, even outside of the moisture plume. Given the
"dry slot" that is being produced by the troughing upstream, there
is a very sharp moisture gradient, which may translate to the
southeastern potion of San Diego County having a much better
chance of seeing storms later today, while the northwestern
portion may remain mostly dry.

By later this evening and through tonight, more of this moisture
plume will continue to move up from the south and over the region,
with likely a mid level cloud shield and intermittent showers
possible, for even the coastal and inland areas overnight. By
tomorrow, the area of low pressure associated with this weakening
tropical system will become absorbed into the trough to our south
and increasing southerly flow with more instability will give way to
a better chance of showers and thunderstorms for tomorrow,
especially over the mountains and deserts. An isolated storm over
the mountains can`t be ruled out during the afternoon on Saturday,
otherwise conditions will become much drier and cooler.

The rest of the weekend though the end of next week...

The forecast still appear to be on track with the system becoming
sheered off towards the east by early Saturday morning, with chances
of precipitation diminishing as it does and a temporary drying trend
on Sunday. With much more influence from the trough upstream, and
the will carry into next week, as a series of deepening troughs
bring bouts of light rain and cooler temperatures to southern
California. Some of the deterministic models are also hinting at a
possible impactful area of low pressure which could potentially
given portions of the region very beneficial amounts during the
mid part of next week. Temperatures could get much colder, and
there could even be some of the higher elevations getting
measurable snow for the first time of this year`s rainy season.
&&

.AVIATION...
092030Z....BKN high clouds based 6000-9000 feet through Friday.
Scattered -SHRA and isolated TSRA through Friday. Greatest chances
for TSRA in the afternoons/evenings over mountains and deserts. Any
TSRA could lower cloud bases to 4000 feet MSL briefly, and could
bring gusty winds and reduced vis in +RA.

&&

.MARINE...
Northwest winds occasionally exceeding 20 knots around San Clemente
Island during the afternoons and evenings Friday and Saturday. There
is a slight chance of thunderstorms through Friday, most likely
during the afternoons. Lightning, erratic winds, choppy seas, and/or
reduced visibility in heavy rain is probable in the vicinity of any
thunderstorm.

&&

.BEACHES...
There is a 5-15% chance of thunderstorms producing lightning
today and Friday, most likely during the afternoons.

&&

.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...Stewey
AVIATION/MARINE/BEACHES...KW