San Ysidro, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

080
FXUS66 KSGX 221641
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
941 AM PDT Thu May 22 2025

.SYNOPSIS...
High pressure aloft will weaken with a low pressure system moving
inland through California on Friday night. High temperatures will
cool from around 10 degrees above average today to within a few
degrees of average on Saturday. Sunday will be around 5 degrees
warmer, then gradual cooling to around average for next Wednesday.
There will periods of stronger and gusty southwest to west winds
for the mountains and deserts during the afternoon and evening
for today and Thursday with the stronger gusts today to 30 to 40
mph and on Thursday to 35 to 45 mph. The marine layer will deepen
into Saturday with night and morning coastal low clouds spreading
farther inland into the valleys each morning through Saturday.
Coastal low clouds won`t extend as far into the valleys on Sunday.
For the early and middle part of next week, the marine layer will
be deepen with night and morning coastal low clouds extending
inland across much of the inland valleys with slower or more
limited afternoon clearing near the coast.

&&

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

Update: Areas of fog within some of the inland areas is continuing
to dissipate, and will continue to do so throughout the next couple
of hours from east to west. The marine layer will remained more
confined to the coastal areas until around Noon. By afternoon, most
areas should be cleared out, although there could still be some
locations right along the coast that could have skies intermittently
become broken to overcast throughout the afternoon.

Models have remained on track for weak troughing moving in
to allow for increased onshore flow and cooler temperatures, which
will be much closer to the seasonal average for this time of year.
There will continue to be more of a push of the marine layer, and
some areas of drizzle, or even light rain against the foothills,
which may occur by late tonight through tomorrow morning. Tomorrow
will likely be the coolest day of the week for most locations, then
there will be a slight warmup for Sunday.

(Previous discussion submitted at 243 AM):

.SHORT TERM (Today through Saturday)...
High pressure aloft will begin to weaken today with a low pressure
system moving inland through California on Friday night. High
temperatures will cool from around 10 degrees above average today
to within a few degrees of average on Saturday. With the cooling,
high temperatures on Saturday will range from the mid to upper 60s
near the coast to the mid 70s to lower 80s for the Inland Empire
with the lower deserts in the mid to upper 90s.

The marine layer is slowly deepening early this morning.
Satellite imagery shows more widespread low clouds spreading
inland past Interstate 5 in Orange County and into the far
western valleys in San DIego County. Deepening of the marine layer
to around 1500 feet is expected for this morning, 2000 feet for
Friday morning, and 2500 feet for Saturday morning. Coastal low
clouds will spread farther into the western valleys for early
Friday morning, and into portions of the inland valleys for early
Saturday morning.

Onshore flow will strengthen for today and Thursday. There will
periods of stronger and gusty southwest to west winds for the
mountains and deserts during the afternoon and evening for today
and Thursday with the stronger gusts today to 30 to 40 mph and on
Thursday to 35 to 45 mph.

&&

.LONG TERM (Sunday through Wednesday)...
High pressure aloft for Sunday will result in around 5 degrees of
warming. Then gradually cooler for Monday through Wednesday with
high temperatures for next Wednesday near average. The marine
layer will decrease in depth to around 2000 feet on Sunday with
coastal low clouds not extending as far into the valleys for early
Sunday.

For the early and middle part of next week, a weak upper level
low pressure system may develop in the vicinity of southern
California. The marine layer will deepen with night and morning
coastal low clouds extending inland across much of the inland
valleys with slower or more limited afternoon clearing near the
coast.

&&

.AVIATION...
221600Z...Coast...Low clouds (based 400-1000ft MSL) and fog that
moved in about 10 miles inland this morning are now efficiently
eroding from east to west and should fully clear by 17z this
morning. Visibility has been gradually improving, but VIS down 2-5SM
remains possible for coastal mesas and inland valleys until the
clouds clear. Marine layer clouds redevelop again tonight, pushing
ashore as early as 02-03z with slightly higher bases - likely above
700ft MSL with better visibility along the coasts and western
valleys, but VIS restrictions focused more within inland higher
terrain. Clearing Friday morning expected at a similar time as this
morning, around 17-18z.

Elsewhere...Clear with unrestricted VIS through Friday morning. West-
northwest wind gusts locally 25-35 kts this afternoon within
mountain passes and along desert mountain slopes strengthen to 35-45
kts Friday afternoon.

&&

.MARINE...
Winds gusting near 20 kts near San Clemente Island on Friday
afternoon, otherwise, no hazardous marine conditions are expected
through Tuesday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

UPDATE...Stewey
PUBLIC...17
AVIATION/MARINE...Munyan