177
FXUS66 KSGX 211949
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1249 PM PDT Sat Mar 21 2026

.SYNOPSIS...
Slight cooling through Sunday, though warm, above average
temperatures persist, with a return of marine layer low clouds and
fog at the coast during the mornings. Slight warming next week as
weaker high pressure builds back into the region, with
temperatures 10-25 degrees above average through at least Friday.

&&

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

Intense, early season high pressure that brought unseasonal,
multiple-record breaking heat has finally weakened and shifted
eastward as a low pressure system in the Gulf of Alaska finally
flattens the persistent ridge that covered the western half of the
U.S. for the last week. Compared to temperatures at noon
yesterday, today`s noon temperatures are anywhere from a degree
to twelve degrees cooler. Sunday`s high temperatures will be
another 2-6 degrees cooler as a small, transient low moves through
the region. Despite this, we`re not close to being out of the
woods in terms of unusually warm temperatures, with even Sunday`s
high temperatures remaining 5-20 degrees above average.

As heights aloft drop and pressure gradients turn onshore, our
long-absent marine layer will make a return to coastal regions
mornings over the weekend into early next week, though a somewhat
patchy one at points. Persistent high pressure will keep clouds to
within 10-15 miles of the coast or so, and low enough that patchy
mist and fog are likely over coastal highlands. Onshore flow will
also lead to breezier afternoon and evening winds today through
Monday for the mountains and deserts, with areas locally gusting
20-35 mph this evening.

Ridging moves back over the region Monday-Tuesday, then amplifies
through mid-week as it moves eastwards into the desert southwest.
As a result, temperatures will increase again Monday-Wednesday by
a degree or two each day, but not to the extent of this previous
week. Temperatures Wednesday will be 10-25 degrees above average
for this time of year. Coastal areas will remain in the mid to
high 70s, with 80s to low 90s in the valleys, low to mid 90s in
the IE and high desert, 70s in the mountains, and mid 90s to about
101 in the low deserts. Several daily temperature records are
likely to be tied or broken over the next week for inland sites,
but monthly records at least are very unlikely to be challenged.

Little change day to day from mid-week to late week as high
pressure remains over the area and temperatures remain well above
average. A pattern shift does appear to be in our future, however,
with the majority of long range models showing some form of low
pressure trough near the end of the month. High uncertainty
remains as there are some significant model differences, but at
least some cooling is very likely.


&&

.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.

&&

.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...CSP
AVIATION/MARINE...Villafane

NWS San Diego (SGX) Office