Corona California Weather Forecast Discussion

662
FXUS66 KSGX 091601 CCA
AFDSGX
Area Forecast Discussion...CORRECTED
National Weather Service San Diego CA
901 AM 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...
Update: Priscilla continues to weaken at this hour, and the remnants
are beginning to stream up over the region this morning, which has
allowed for some showers and a few very high-based embedded
thunderstorms. The moisture plume appears as if it is going to be
located mostly over the southeastern half of the CWA throughout the
day. Although, 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" the 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 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. The forecast still appears 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. An isolated storm over the mountains can`t be ruled
out during the afternoon on Saturday, otherwise conditions will
become much drier and cooler, 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.
(Previous discussion submitted at 259 AM):
Patches of low clouds persist in the San Diego County coastal areas
and valleys this morning but are not showing signs of increasing
in coverage while mid and high clouds are moving in from the south
on the edge of a plume of deep-layer moisture from Tropical Storm
Priscilla. The bulk of the moisture from Priscilla will stay to
the south and east of San Diego County but enough moisture should
make it into the region for a chance of showers and potentially
isolated tstms from the deserts to the coast and from San Diego
County north to southwestern San Bernardino County, beginning
later this morning. Showers will be mostly light but heavier
showers could develop this afternoon into this evening. Scattered
light showers could continue tonight into Friday morning. More
widespread and heavier showers/tstms are likely Fri afternoon/evening,
and light showers could persist into Saturday morning. Due to the
showery nature, rainfall amounts will vary greatly but will range
from a few hundredths in the coastal areas and valleys to nearly
an inch in some mountain locations between today and Saturday.
Heavier showers or tstms could produce locally heavy rainfall, as
much as 0.60 inch per hour. By Friday night, Priscilla will become
absorbed into the southwesterly flow between the low pressure
system to our northwest and the high pressure centered near the
TX/MX border. As this process continues, available moisture will
be transported to the northeast.
Sunday and Monday will see a return to dry and more typical
conditions as the low pressure system moves inland and the upper
closed low becomes an open wave over the Rockies...leaving an area
of broad troughing over the western US. Temperatures will remain
below seasonal averages and the marine layer low clouds will
return for Sat and Sun nights.
For next Tue and Wed, another low pressure system moving south
over the west coast will bring cooler and windy conditions along
with more chances for precipitation. At this time, the spread
among model solutions makes the forecast more uncertain but a
plurality of ensemble solutions across model platforms indicate
precipitation moving in from the northwest as early as Tuesday
morning and lasting through Wed morning.
&&
.AVIATION...
091530Z....Clouds at or above 10000 feet will thicken and lower at
times to 6000-9000 feet. Isolated -SHRA and sprinkles through
tonight. Isolated TSRA after 21Z Thu, most likely 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 today 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

NWS SGX Office Area Forecast Discussion