112
FXUS66 KSGX 291032
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
332 AM PDT Tue Sep 29 2026

.SYNOPSIS...
Strengthening high pressure will bring warming this week. A long-
duration heat wave, with widespread Major to locally Extreme
HeatRisk for the coast and valleys, is likely for this weekend
through much of next week into the following weekend. Record warm
overnight temperatures are likely for the coast and valleys for
Saturday through Monday.

&&

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

.SHORT TERM (Today through Thursday)...
A thunderstorm developed in the area around Indio Hills in the
Coachella Valley on Monday evening with heavy rainfall resulting
in flash flooding, strong gusty winds, and more than 1000
lightning flashes and strikes of all types. There have been
reports of mud, rocks, and boulders covering portions of Dillon
Road near and to the northwest of Indio Hills. A Caltrans sensor
along Interstate 10 east of Dillon Road had gusts to 44 mph
between 9:30 PM and 10:30 PM.

A closed low pressure system centered over southern Nevada will
move eastward across Arizona today with a period of weak offshore
lower level flow developing today. For this morning into this
afternoon, north winds will gust to 35 to 45 mph in the San
Bernardino County mountains with north to northwest winds in
portions of the Coachella Valley gusting to 30 to 40 mph. There
will also be gusty north winds to 20 to 30 mph in portions of the
Inland Empire. Onshore flow will return on Wednesday and weaken on
Thursday.

High pressure aloft off the California coast will move across
California and slowly strengthen through Thursday. High
temperatures for today will warm a few to as much as 5 to 10
degrees. On Wednesday, high temperatures will warm 5 to locally 10
degrees while coastal areas cool a few degrees with the return of
onshore flow. On Thursday, high temperatures will warm a few to
around 5 degrees with the greatest warming for the inland
valleys.

High temperatures on Thursday will be a few degrees above average
for the lower deserts and 5 to 10 degrees above average elsewhere.
High temperatures on Thursday will range from around 80 near the
coast to the 90s for the Inland Empire with the lower deserts in
the upper 90s to around 100.

&&

.LONG TERM (Friday through Monday)...
High pressure aloft will strengthen into the weekend with periods
of weak easterly offshore flow during the weekend. Not much
change is expected in high temperatures on Friday for the
mountains and deserts while the coast and valleys warm 4 to 8
degrees. High temperatures on Friday for the coast and valleys
will range from the 80s near the coast to the upper 90s to 105
for the Inland Empire with Moderate to locally Major HeatRisk for
the coast and valleys.

Not much change in high temperatures is expected for mountains and
deserts for the weekend while coastal areas warm another 5 degrees
on Saturday with only slight additional warming on Sunday. Low
temperatures for coastal areas will warm from around 70 on
Saturday to the lower to mid 70s on Sunday. Widespread Major
HeatRisk is expected on Saturday for the coast into the western
valleys with Major to isolated Extreme HeatRisk on Sunday.

High temperatures for the weekend will range from around 5 degrees
above average for the lower deserts to as much as 15 to 20 degrees
above average for coastal areas into the western valleys. High
temperatures for the weekend will range from the mid 80s to around
90 near the coast to the mid 90s to 105 for the valleys with the
lower deserts around 100.

There could be periods of gusty east winds during the weekend for
the coastal slopes of the mountains into the inland valleys with
gusts to 25 to 35 mph.

A long-duration heat wave, especially for the coast and valleys,
is likely to persist for much of next week into the following
weekend.

&&

.AVIATION...
290530Z...Coast...Patchy low clouds based at around 1500-2000
feet MSL will continue overnight. Any cigs at coastal airports
would be very brief and intermittent. Otherwise, mostly clear
through Tuesday evening.

Otherwise...mostly clear skies through Tuesday, except for cumulus
based at around 9000 feet MSL over mountains and deserts 18-01Z
Tuesday.

&&

.MARINE...
With winds in the outer waters diminishing, no hazardous marine
conditions are expected tonight through Friday.

&&

.BEACHES...
Southeast swell from Hurricane Polo will continue to generate
elevated surf with sets to 7 feet into Tuesday in northern Orange
County. There is a high risk for strong rip and longshore currents
through Tuesday. In addition to elevated surf, high tides will peak
at 6.8-7.1 feet during the late mornings Tuesday and Wednesday,
highest on Tuesday. High tides and elevated surf will combine to
generate minor coastal flooding in low lying areas and coastal
erosion. A Coastal Flood Advisory is in effect through Wednesday
afternoon.

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

&&

.FIRE WEATHER...
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. There could be periods of
gusty east winds along and below the coastal slopes of the
mountains into the inland valleys with gusts to 25 to 35 mph on
Saturday and 30 to 40 mph on Sunday with lowest daytime relative
humidity for the coastal slopes of the mountains into the valleys
falling to 15 to 25 percent with elevated fire weather conditions.
There could be additional periods of mostly weak offshore flow
next week, but with lower confidence in the timing and other
details.

&&

.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 Wednesday for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...17
AVIATION/MARINE...MM

NWS San Diego (SGX) Office