313
FXUS66 KSGX 021212
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
512 AM PDT Tue Sep 2 2025

.SYNOPSIS...
Monsoonal moisture will increase from the southeast this morning
with scattered showers and thunderstorms across much of the area
for today. Thunderstorms would produce cloud-to- ground
lightning, brief heavy downpours, and strong gusty winds to 40 to
50 mph. Chances for mainly afternoon and early evening
thunderstorms, mainly for the mountains and deserts, will
gradually decrease for Wednesday through Friday. Then drier and
gradually cooler for the weekend into early next week.

&&

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

.SHORT TERM (Today through Thursday)...
Upper level low pressure will move northwestward across the area
today with monsoonal moisture increasing from the southeast
today. This will bring showers and a chance of thunderstorms over
much of the area today with the greatest chances over the
mountains and high desert for this afternoon.

Radars show showers and thunderstorms extending from around El
Centro to Lake Havasu City at 5 AM. These will begin moving into
the mountains and deserts in San Diego County by 6 AM and into the
Coachella Valley after 6 AM. Brief downpours, cloud-to-ground
lightning, and strong gusty winds are expected as these showers
and thunderstorms move toward the west across San Diego and
Riverside Counties.

The incoming 12Z NKX sounding shows layers with greater saturation
around 550 mb and around 350 to 400 mb. Some of the higher
resolution models show the potential for strong downdraft winds
from high-based showers and thunderstorms. The greater chances for
heavier rainfall are over the mountains where the depth of the dry
air below the mid level cloud bases is less.

The coast and valleys will cool a few to around 5 degrees through
Thursday with lesser changes for the deserts. High temperatures on
Thursday will range from the mid 70s to lower 80s near the coast
to the 90s for the Inland Empire with the upper 90s to 102 for
the lower deserts.

&&

.LONG TERM (Friday through Monday)...
There will be gradual cooling and drying through Monday with
Monday high temperatures around 5 degrees below average for inland
areas. High temperatures on Monday will range from the 70s near
the coast to the mid 80s to lower 90s for the Inland Empire with
the upper 90s to 102 for the lower deserts. There is a chance of
showers and thunderstorms for the mountains and deserts for Friday
afternoon and a slight chance on Saturday afternoon.

&&

.AVIATION...
020930Z...Patchy and intermittent coastal low clouds with isolated
CIGs 400-600 feet MSL and vis 0-5SM through 15Z. Regionwide...
increasing clouds AOA 10000 feet MSL with SCT -SHRA and isold -TSRA
after 16Z. This will continue all day, but after 00Z gradually
migrating inland with decreasing chance after 06Z. Gusty and erratic
winds, low visibility, and lightning will accompany any TSRA, along
with lower bases 6000-9000 feet MSL.

&&

.MARINE...
SCT -SHRA and isold -TSRA 16-02Z. Gusty winds and low visibility
near any TSRA. After 02Z, no hazardous marine conditions are
expected through Saturday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 6 PM PDT this evening for Orange County
     Inland Areas-San Bernardino and Riverside County Valleys-
     The Inland Empire-San Diego County Valleys-Santa Ana
     Mountains and Foothills.

PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE...MM