612
FXUS66 KSGX 301130
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
430 AM PDT Wed Sep 30 2026

.SYNOPSIS...
Strengthening high pressure aloft will bring a warming trend with
a long-duration heat wave likely for this weekend through much of
next week into the following weekend. The highest HeatRisk is
expected for the coast and valleys with widespread Moderate or
greater HeatRisk for the coast and valleys for Friday through next
week with widespread Major to Extreme HeatRisk for the weekend
into next week for inland coastal areas into the western valleys.

&&

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

...UPDATED AVIATION DISCUSSION...

.SHORT TERM (Today through Friday)...
High pressure aloft will strengthen across California through
Friday with 500 mb heights rising to near or slightly above the
90th percentile. This will bring a warming trend into the weekend
with warming for today ranging from a few degrees near the coast
to around 10 degrees for the mountains. The warming for Thursday
and Friday will be mainly for the coast and valleys.

High temperatures for today will be mostly a few to around 5
degrees above average, ranging from the mid to upper 70s near the
coast to the upper 80s to mid 90s for the Inland Empire with the
lower deserts in the upper 90s. On Friday, high temperatures for
the coast and valleys will be 10 to 15 degrees above average to
locally 15 to 20 degrees above average for portions of the western
valleys in San Diego County. High temperatures on Friday will
range from the 80s near the coast to the upper 90s to 105 for the
Inland Empire with the lower deserts around 100. This will result
in Moderate to Major HeatRisk for the coast and valleys on Friday.

There could also be weak easterly offshore winds on Friday with
gusts to 20 to 30 mph along the coastal slopes of the mountains
into the adjacent inland valleys in Riverside and San Diego
Counties. Areas of late night and early morning low clouds for
coastal areas will become much patchier by the weekend.

&&

.LONG TERM (Saturday through Tuesday)...
A weak trough of low pressure moving inland into northern and
central California on Sunday and Monday could bring slight cooling
for coastal areas for Sunday through Tuesday followed by weaker
onshore flow near the coast returning by Wednesday.

ECMWF ensemble output for Campo is strongest with the offshore
winds on Saturday with uncalibrated gusts to around 40 mph. High
temperatures on Saturday could be another 5 or so degrees warmer
for coastal areas into the western valleys with high temperatures
ranging from around 90 near the coast to the upper 90s to 108 for
the valleys with the lower deserts around 100. Low temperatures
on Saturday will be mostly in the lower 70s for coastal areas,
around 10 degrees above average. Widespread Major HeatRisk is
expected for the coast and valleys on Saturday.

For Sunday through Tuesday, low temperatures for the coast into
the western valleys will warm into the lower to mid 70s, 10 to 15
degrees above average. Moderate HeatRisk will continue for the far
inland valleys with Major to Extreme HeatRisk for inland coastal
areas into the western valleys.

This long-dursation heat wave, with highest HeatRisk for the
coast and valleys, may continue through much of next week into
the following weekend.

&&

.AVIATION...
301130Z...Coast/western valleys: Low clouds based at around 1000-
1200 feet MSL will continue this morning, most uniform in San Diego
County, more patchy in Orange County. Scatter out should occur by 16-
18Z. Low clouds based around 1000 feet MSL to move ashore 03-08Z
this eve and locally into western valleys by sunrise Thursday.

Otherwise...clear skies today and tonight.

&&

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

&&

.BEACHES...
High tides will peak at 6.8-7.1 feet between 11 AM and 1 PM today,
leading to minor coastal flooding in low-lying areas and coastal
erosion. A Coastal Flood Advisory is in effect through this
afternoon.

Please note: mentioned tide predictions in the Advisory have been
adjusted to reflect actual measured tide observations.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Coastal Flood Advisory until 5 PM PDT this afternoon for Orange
     County Coastal Areas-San Diego County Coastal Areas.

     Extreme Heat Watch from Friday morning through Wednesday evening
     for Orange County Coastal Areas-Orange County Inland Areas-
     San Bernardino and Riverside County Valleys-The Inland
     Empire-San Diego County Coastal Areas-San Diego County
     Valleys-Santa Ana Mountains and Foothills.

PZ...None.

&&

$$

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