737
FXUS66 KSGX 190053
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
553 PM PDT Sat Apr 18 2026

.SYNOPSIS...
Inland areas will warm this weekend while coastal areas begin to
cool on Sunday as onshore flow returns. Onshore flow will strengthen
and spread cooling inland on Monday as a low pressure system
moving into California brings cooler and breezy conditions for the
middle of next week, along with a slight chance of precipitation
Tuesday afternoon into Wednesday morning. Cool weather and breezy
onshore flow persist for the remainder of the week.

&&

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

Hazy sunshine this afternoon under a ridge of high pressure, with
variable high clouds ahead of a weak upper level trough approaching
from the west. Temperatures are close to what they were yesterday
in the coastal areas while inland they are as much as 10-12
degrees higher. Surface pressure gradients remain weakly offshore
and helped to prevent low clouds from spreading inland last night.
In the mountain passes and foothills, northeast to east winds are
still occasionally gusting 25-35 mph but will continue to weaken
while a sea breeze is developing in the coastal areas and valleys.

The high pressure ridge will shift eastward over the next several
days as a vigorous low pressure system moves in from the northwest.
Temperatures will generally remain several degrees above seasonal
average through Monday as we remain in the warm sector ahead of
the approaching low pressure system. Highs will be in the low to
mid 70s along the coast, upper 70s to mid 80s for inland coastal
areas and valleys, upper 50s to upper 60s in the mountains, mid to
upper 70s in the high desert, and upper 80s to around 90 in the
low desert. A return of onshore flow will spread cooling inland
west of the mountains, and bring more widespread low clouds along
the coast tonight into Sunday morning.

Onshore flow strengthens Monday through Wednesday as the low
pressure system moves inland through California. Gradual cooling
takes place through this period, with highs decreasing to around 3
to 8 degrees below normal by Wednesday. Wednesday will likely be
the coolest day as the upper level trough axis moves inland and
colder air filters into SoCal from the northwest. Gusty southwest
to west winds develop over the mountains, deserts, and through
the passes each afternoon and evening, peaking on Tuesday as the
closed upper low moves inland to our north. Wind gusts around
30-45 mph will occur along the desert mountain slopes, below the
passes, and into the deserts Tuesday, with locally higher gusts
below the San Gorgonio Pass.

The passage of the upper level trough will bring a slight chance
of showers sometime late Tuesday into Wednesday. Forecast details
are still somewhat uncertain but most likely we will be on the
southern periphery of the moisture with limited potential for
precipitation. The National Blend of Models probabilities of
measurable rain (at least 0.01") for the 24 hr period ending at 5
am Wednesday range from around 20% for Orange County/far west
Inland Empire and the mountains to 10-15% for the remainder of the
Inland Empire, high desert, and San Diego County coasts and
valleys, and less than 5% in the low desert. Chances of at least
0.10" is around 15%-20% along the south slopes of the San
Bernardino Mountains and less than 10% elsewhere. A second short
wave moves through sometime late Wednesday, but is currently
forecast to be to dry and unlikely to produce any precipitation.

We will remain under broad troughing aloft through the end of next
week, continuing the cooler weather with high temperatures a few
degrees below normal and breezy conditions in the mountains and
deserts each afternoon. The marine layer will also be fairly deep
during this time, but the marine inversion will likely be so weak
that low cloud coverage will be patchy in the coastal areas and
valleys once the main trough axis passes on Wednesday.

&&

.AVIATION...
190000Z...Mostly clear skies and VFR conditions through this
evening. Patchy low clouds building in from the south with higher
confidence to cover areas of coastal San Diego County between
09-16z Sunday. Cigs near 1300-2000ft MSL with a 50-70% chance of
BKN conditions at VCTY KSAN. Increasing south and west winds
across the desert slopes into the deserts Sunday afternoon/evening
near 20-30 kts.

&&

.MARINE...
No hazardous marine conditions are expected through Tuesday.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE...Munyan

NWS San Diego (SGX) Office