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000
FXUS66 KSGX 181539
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
839 AM PDT Thu Apr 18 2024

.SYNOPSIS...
A weak low pressure system moving inland through southern
California will bring cooling through Friday, gusty southwest to
west winds for the mountains and deserts during the afternoons and
nights with the stronger gusts to 50 mph, and deepening of the
marine layer with night and morning coastal low clouds extending
inland across much of the valleys by Friday night. Warming for
Saturday and Sunday under high pressure with the marine layer
becoming shallower. Then a cooling trend for Monday into the
middle of next week as low pressure develops near the West Coast.

&&

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

.Morning Update...
A thick shield of high clouds over the region is accompanied by a
deeper marine layer, blanketing coastal areas in clouds and haze.
Per latest HREF guidance, low clouds will begin to mix out later
this morning with the shield of high clouds associated with a weak
shortwave to push east. Better clearing with more sunshine can be
expected from west to east today, most likely by the afternoon
hours. Depending on how quickly skies clear, temperatures may be
slightly cooler than anticipated across San Diego County today.

With the passing trough, winds will increase across the mountains
and deserts, strongest and most widespread on Friday. No major
changes to the forecast this morning, but we will keep an eye on
how hot the lower deserts will be this weekend, as well as a slow
weather pattern change by next week.

.SHORT TERM (Today through Saturday)...
Subtropical high clouds will thicken and spread inland across
southern California today with a weak low pressure system moving
inland through southern California tonight and Friday.

The marine layer will deepen into Friday with coastal low clouds
and fog extending inland into the far western valleys this
morning, farther into the valleys for tonight into Friday morning,
and inland across much of the valleys for Friday night and
possibly onto the lower coastal slopes of the mountains.

The will be cooling for today and Friday. High temperatures for
the coast and valleys for Friday will be a few to around 5 degrees
below average for the coast and valleys with the deserts still
around 5 degrees above average. There will be gusty southwest to
west winds for the mountains and deserts this afternoon and
tonight with the stronger gusts to 40 to 50 mph with another round
of gusty winds for Friday afternoon and night with the stronger
gusts to 45 to 55 mph. Saturday will be warmer with high
temperatures a few degrees warmer to around 5 degrees warmer for
the mountains.

&&

.LONG TERM (Sunday through Wednesday)...
High pressure aloft will continue the warming on Sunday with the
marine layer becoming shallower and night and morning low clouds
and fog patchier and closer to the coast. With the warming, high
temperatures near the coast will be a few degrees above average on
Sunday to around 8 to 12 degrees above average for the mountains,
high desert, and inland valleys. NBM chances for Palm Springs to
reach 100 or higher on Sunday have decreased to 65 percent. If
Palm Springs doesn`t have its first 100 degree day for 2024 on
Sunday, it could be delayed until some time in May.

There will be a cooling trend for Monday through Wednesday as a
low pressure system develops in the vicinity of the California
coast. There remain model differences in the placement and
details. NBM has high temperatures on Wednesday cooling to around
5 degrees below average at lower elevations to 8 to 12 degrees
below average the mountains and inland valleys. The marine layer
is expected to deepen with night and morning coastal low clouds
extending inland across much of the valleys by Wednesday and
possibly onto the lower coastal mountain slopes. There will also
be gusty southwest to west winds for the mountains and deserts for
each afternoon and night.

&&

.AVIATION...
181530Z...Coast/Valleys...Low clouds and fog will continue with
bases 500-900 feet MSL and tops to 1200 feet. Vis 0-5SM over mesas
and higher coastal terrain. Clearing will occur in most areas 16-
18Z. Low clouds to push ashore after 02-03Z this evening and into
western valleys after 10Z Friday. Bases should be around 1200-1600
feet MSL with local vis reductions along inland extent.

Otherwise...BKN high clouds at/above 20000 feet MSL will continue
through 23Z, SCT thereafter. VIS will remain unrestricted.

&&

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

&&

.BEACHES...
A long-period swell from the Southern Hemisphere will continue to
bring surf up to 6 feet this morning, especially on south-facing
beaches in Orange County, before gradually subsiding thereafter.
This will generate a high rip current risk.

&&

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


&&

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

&&

$$

MORNING UPDATE/PREVIOUS PUBLIC...APR/17
AVIATION/MARINE...Adams