112
FXUS66 KSGX 040409
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
909 PM PDT Tue Jun 3 2025

.SYNOPSIS...
An upper level low pressure system will continue to provide a
chance of showers and thunderstorms through tonight across
Southern California and the coastal waters; decreasing by early
tomorrow morning. There is a slight chance for showers and
thunderstorms tomorrow afternoon, mainly for the mountains. Drier
with a warming trend for Thursday into the weekend with high
temperatures for Sunday and Monday around 4 to 8 degrees above
average for inland areas. Dry and warm conditions continue into
early next week.

&&

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

Update: The upper level low which has been influencing the region
with widely scattered showers and thunderstorms this afternoon and
evening is continuing to slowly propagate east, which has allowed
the cluster of thunderstorms to begin shifting southward from the IE
and into San Diego County. There have been several storms which have
became strong enough to result in brief heavy downpours and hail up
to a half an inch in Hemet earlier this evening (confirmed by
photo), which has prompted the issuance of a few Flood Advisories
and one Flash Flood Warning (for southern San Bernardino and
northern Riverside counties). Unconfirmed reports of some
locations receiving more than an inch of rainfall so far have been
coming in. These showers and thunderstorms will continue to slide
southward ever so slowly over the mountains and into the inland
areas from east to west over the course of the next couple of
hours. It has been interesting with more stable conditions near
the surface with the marine layer in place and more unstable
conditions aloft with the thunderstorms, which have been obscured
by the lower clouds. There could still be some moderate to heavy
rainfall with these, and flash flooding concerns will continue
through the early evening hours but then as the U/L low continues
to move east with the more convergent quadrant of the low coming
overhead, as well as the overall stabilization of the lower levels
with the loss of surface heating, these should continue to
gradually weaken and become more of just showers as they make
their way into southern San Diego County.

The influence of the U/L low tomorrow could still allow for some
thunderstorms to build during the afternoon hours over the
mountains, and possibly deserts, with a much lesser chance of
impacting the coastal and inland areas given the mid to upper level
wind flow and more likely movement of storms. Having said that, a
rogue storm for these locations is not out of the question,
especially within the IE. It will still be on the relatively cooler
side tomorrow, with temperatures slightly below the seasonal average
for this time of year. After that, conditions will continue to
gradually dry and warm throughout the rest of the week and into the
weekend as slight ridging building from the south in the long wave
pattern continues to become more prevalent.

(Previous discussion submitted at 300 PM):

This afternoon...Organized bands of showers and tstms have
developed over the San Bernardino Mountains and over the coastal
waters about 10 miles east of San Clemente Island. These bands are
likely to shift south and east as the closed upper low continues
to move in that direction. The convective cells will continue to
move northwest with the flow around the upper low. This will
bring ISOLD-SCT showers and tstms to the mountains and slight
chances for showers/tstms elsewhere. Thunderstorms could produce
locally gusty winds, small hail, lightning and periods of locally
heavy rain. Minor flooding will be possible in those areas that
experience heavy rain. The marine layer low clouds are clearing
but could return late tonight.

From previous discussion...
The closed upper low will continue to move south and east through
tonight, becoming an open wave over AZ by late Wednesday morning.
It will produce chances for SCT/ISOLD showers/tstms across all
parts of SoCal into early Wed morning. Residual moisture and
daytime heating could maintain chances for showers/tstms over the
mtns again Wed afternoon.

Some high-resolution WRF models show rainfall totals of as much
as 2-3 inches in the mountains while others show around 1 to 1.5
inches. NBM probabilities for one-half inch of rainfall is as
much as 30 percent for portions of the San Bernardino County
mountains and adjacent desert areas with isolated locations with
around a 10 percent chance for one-inch or more of rainfall.
Shower and thunderstorms are expected to decrease late tonight
with a slight chance of showers and thunderstorms on Wednesday
afternoon, mainly in the mountains.

High temperatures for today and Wednesday will be mostly a few to
around 5 degrees below average with Thursday a few degrees warmer
with drying. Warm and dry weather with seasonal marine layer low
clouds and fog during the nights and mornings will continue into
early next week under broad low pressure troughing.

&&

.AVIATION...
040310Z....SHRA/TSRA will continue to move south across the area and
gradually weaken through 10Z. CB bases near 10 kft MSL and tops to
25-30 kft this evening with local VIS 3-5 SM and small hail in TSRA.
Otherwise stratus with bases 1300-2000 ft MSL with tops to 3000 ft
MSL filling in across the remaining portions of the coastal basin
overnight, clearing in the inland valleys 15-18Z and near the coast
18-20Z, though portions of the San Diego County coast may remain BKN
through the afternoon. ISO SHRA/TSRA over the mountains and deserts
developing around 19Z and dissipating around 05/02Z. Low clouds with
similar bases/tops as tonight spreading back inland Wednesday
evening.

&&

.MARINE...
Small (10%) chance of thunderstorms near the San Diego County coast
trough about 10 PM. Storms may produce cloud-to-water lightning and
small hail. No additional hazardous marine conditions are expected
later tonight through Sunday.

&&

.BEACHES...
Elevated surf of 3 to 5 feet with sets to 6 feet are expected for
the rest of today, primarily for south to southwest facing beaches.
There is a 10% chance of thunderstorms at the beaches through about
10 PM. A Beach Hazards Statement remains in effect through 2 AM
Wednesday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 2 AM PDT Wednesday for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

UPDATE...Stewey
PUBLIC...PG
AVIATION/MARINE...SS