859
FXUS66 KSGX 191133
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
433 AM PDT Sun Apr 19 2026

.SYNOPSIS...
Cooler west of the mountains today and warmer inland. A low
pressure system moving into California brings cooler and breezy
conditions Monday through 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...

...New Aviation and Marine Discussion...

Scattered high clouds are lifting northeast across the region this
evening well ahead of an upper level low off the Pacific Northwest
coast. With the high cloud coverage, low clouds off the coast
remain sparse. Patchy low clouds may develop over the coastal
areas and far western valleys later this morning, clearing by
mid-morning.

An upper level ridge currently near the Lower Colorado River
Valley will shift slightly eastward and amplify over the Desert
Southwest today, bringing warmer weather in the mountains and
deserts. A stronger sea breeze today will help spread marine air
into the coastal areas and valleys for some cooling. In general
high temperatures will be around 3-8 degrees above normal today.
The upper level low gradually drops south today and then moves
towards the coast on Monday, bringing more widespread cooling with
increasing southwest to west winds in the mountains and deserts.
The marine layer will deepen with this approaching low, with more
widespread low clouds tonight into Monday morning spreading into
parts of the inland valleys.

A negatively tilted short wave associated with the upper low lifts
across So Cal Tuesday afternoon and evening. We`ll be on the tail
end of this system with limited moisture to work with. The 00Z
ensembles have trended drier with this trough with ensemble mean
precipitation now down to a couple hundredths of an inch for the
coastal areas and valleys. Chances of measurable precipitation (at
least 0.01") range from around 50% along the LA County boarder and
coastal mountain slopes to 30% in southern San Diego County, 25%
in the high desert, and less than 10% in the low desert. Chances
of 0.10" or more have decreased since yesterday, now down to
around 5-25% for the mountains westward, highest near the LA
County border and decreasing to the southeast. The bigger impact
from this trough will be strong and gusty southwest to west winds
in the mountains and deserts Tuesday afternoon through Tuesday
night when local gusts to 55 mph are possible along the desert
mountain slopes and through the passes. The main trough axis moves
through by Wednesday morning, at which point winds will begin to
weaken. Wednesday will be the coolest day of the week when highs
will be around 5-10 degrees below normal away from the coast, and
up to 3 degrees below normal near the coast.

Weak troughing remains across the Western US for the rest of the
week, maintaining cool weather, a deep marine layer, and breezy
conditions in the mountains and deserts. Another upper low may
develop off the coast in the southern branch of the split flow and
eventually make it towards So Cal late in the week, but there is
still a lot of spread in the ensembles regarding the evolution of
this pattern. If the low develops far enough west that it could
pick up moisture before making it here we will have another chance
at precipitation by early next week, but this pattern is
generally low predictability so don`t count on anything yet.

&&

.AVIATION...
191130Z...Mostly high clouds out there with a small patch of low
clouds coming in at the very southern part of coastal San Diego
County at 1000-1500ft MSL. There is a 40-60% chance of these low
clouds reaching KSAN after 12Z and lasting through 17Z. Low clouds
are expected to redevelop after 04Z Monday mainly along the coast
with higher probabilities for coastal San Diego.

Increasing westerly to southwesterly winds across the desert slopes
into the deserts this afternoon/evening near 20-30 kts.

Otherwise, VFR conditions expected through the TAF period.

&&

.MARINE...
No hazardous marine conditions are expected through Tuesday.
Elevated onshore (northwesterly) wind gusts near 20-25 knots are
possible Wednesday into Thursday.

&&

.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...SS
AVIATION/MARINE...Villafane