Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 281134
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
434 AM PDT Thu May 28 2020

.SYNOPSIS...
Through Saturday, high pressure over southern California will
weaken and move east as a low pressure system well to the
southwest of California moves toward the northeast and into and
through California late Friday and Saturday. Onshore flow will
strengthen, the marine layer will deepen with night and morning
coastal low clouds spreading farther into the valleys, and
cooling will spread inland. Sunday is expected to be a little
warmer. There is greater uncertainty in the forecast for early
next week ranging from warmer with a shallower marine layer to
cooler with a deeper marine layer with more persistent low clouds
for the coast and valleys.

&&

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

.SHORT TERM (Today through Saturday)...
High pressure over southern California will weaken and move east
as a low pressure system well to the southwest of California
moves toward the northeast and into and through California late
Friday and Saturday. Onshore flow will strengthen, the marine
layer will deepen, and cooling will spread inland.

The marine layer has deepened over the past 24 hours. Widespread
coastal low clouds have spread farther into the San Diego County
valleys and may make into the southern and western portions of the
Inland Empire early this morning. Deepening of the marine layer
is expected to continue into Saturday with the night and morning
coastal low clouds extending farther into the valleys each night.
The low clouds could linger near some beaches in the afternoons.

With the deepening of the marine layer, the greatest cooling today
is expected in the valleys. More widespread cooling will spread
inland for Friday and Saturday.

&&

.LONG TERM (Sunday through Wednesday)...
Sunday and Monday may be a little warmer and Tuesday and Wednesday
may be a little cooler. There remain large differences among the
global models and their ensemble members on the placement of an
upper level low pressure system that could be any where from near
southern California to well offshore. The more offshore solutions
would strenghten high pressure over southern California with a
more significant warming trend for Sunday through Tuesday with the
marine layer becoming shallower. The solutions with an upper low
near southern California would be cooler and maintain a deeper
marine layer. For inland areas for early next week, there is a 15
to 20 degree spread in high temperatures between the cooler and
warmer solutions. The current forecast has Monday and Tuesday a
little cooler, then Wednesday a little warmer.

&&

.AVIATION...
280915Z...Coast/Western Valleys...Low clouds based 900-1200 feet MSL
with tops to 1800 feet will continue into western valleys this
morning. Reduced vis 0-5SM at elevations between bases/tops. Scatter
out 16-17Z, but with lingering clouds at some beaches. Low clouds to
move ashore after 02Z this evening with similar bases/vis and extend
farther into western valleys by early Friday.

Inland Valleys/Mountains/Deserts...Mostly clear with unrestricted
vis today and tonight.

&&

.MARINE...
No hazardous marine weather is expected through Monday.

&&

.BEACHES...
A long-period south-southwest swell will bring elevated surf and
high rip current risk Friday through Sunday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 7 PM PDT Friday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...NONE.

&&

$$

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


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