503
FXUS66 KSGX 211809
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1109 AM PDT Sat Mar 21 2026

.SYNOPSIS...
Gradual cooling through the weekend with a return of marine layer
low clouds and fog at the coast. Even with the cooling,
temperatures will remain 15-25 degrees above normal into next
week, highest on Wednesday during the next peak in the heat.

&&

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

...NEW AVIATION DISCUSSION...

Today through tomorrow night...

Currently, low clouds are still nearly absent within the inner
waters of the SoCal bight, and will likely continue to struggle to
develop throughout the morning, with likely just some patchy low
clouds and fog being possible along some of the coastal areas, with
higher confidence along the southern coast of San Diego County.

The very strong ridge overhead that has resulted in record-breaking
heat is finally going to begin to weaken and allow for some relief
in the intense heat, although temperatures will still be well above
average for this time of year. The low deserts still have an Extreme
Heat Warning in place for today as temperatures still look to
approach 110 for some areas. There will be an enhancement in onshore
flow, bringing a slight cooling trend from west to east through
tomorrow. This will help to knock down high temperatures nearly 10
degrees cooler from where they were yesterday for some of the inland
areas by Sunday. This will also help to some of the lower level
moisture to surge in from the west as there is some weak troughing
upstream which will help to influence the marine layer with better
coverage expected overnight Saturday into Sunday morning. There
could also be some patchy fog, which may even be locally dense along
some of the coastal slopes. Winds will become stronger and gusty out
of the west by later this afternoon and through the early evening,
especially across the higher terrain and within the mountains passes
and canyons which are more vulnerable to gusty winds. These winds
look to primarily remain below criteria, and will be gusty again
during the afternoon hours on Sunday, although even slightly weaker.

Monday through Friday...

As the ridge continues to break down, the longwave flow will become
more zonal, then followed by more ridging (although not as strong as
the ridge in place this past week) going into the latter part of the
week, which will bring back a gradual warmup and keep temperatures
still some 15 to 20 degrees above the seasonal average for this time
of year, especially within the inland valleys and IE. There is
pretty good agreement with the ensemble solutions showing slight
ridging becoming the dominant feature again, and then a little
beyond the forecast shows that there could begin a pattern shift
going beginning the following weekend, although this is still too
far out in the forecast to be reliable at this time.

&&

.AVIATION...
211800Z...Currently a patch of low clouds around 300 ft MSL are
hanging out just off the southern San Diego coast. Higher chances
for fog and low clouds for coastal sites this evening beginning
after 02Z Sunday. Cloud bases are expected to be around 300-800 ft
MSL, increasing in coverage 6Z-9Z. Vis restrictions around 2-5SM
with fog along elevated coastal terrain are expected to develop 7Z-
10Z.  Low clouds and fog will begin to clear 16-18Z Sunday.
Otherwise, VFR conditions expected through the period.

&&

.MARINE...Patchy, but not dense, fog out over the local waters
currently. Fog is expected to increase in coverage this evening with
locally reduced visibility under 1 nautical mile possible.
Visibility will improve by late morning Sunday. Otherwise, no
hazardous marine conditions expected through Thursday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Extreme Heat Warning until 8 PM PDT this evening for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass near
     Banning.

PZ...None.

&&

$$

PUBLIC...Stewey
AVIATION/MARINE...Villafane

NWS San Diego (SGX) Office