Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 231032
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
332 AM PDT Tue Apr 23 2019

.SYNOPSIS...
There will be gusty north winds in southwestern San Bernardino
County near and along the coastal mountain slopes and below
passes and canyons into early afternoon. A weak coastal eddy at
times into Thursday will bring areas of night and morning low
clouds and fog with the coastal low clouds spreading a little
farther inland each night. High pressure aloft will expand across
California continuing the warming trend into Thursday for inland
areas. Coastal and valley areas will continue to warm today, but
slight cooling is possible for Wednesday and Thursday if slow
deepening of the marine layer occurs. A slow moving low pressure
system will move inland across southern California around Sunday
night. This will bring cooling and deepen the marine layer onto
the coastal mountain slopes during the weekend. It will also bring
strong and gusty west winds to the mountains and deserts with a
slight chance of light showers, mainly for the coastal slopes of
the mountains into the valleys, for late Sunday into early
Monday.

&&

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

.SHORT TERM (Today through Thursday)...
A low pressure system centered over northwest Mexico early this
morning will continue to move slowly to the southeast as high
pressure aloft over the eastern Pacific expands into California.
This will continue the warming trend through Thursday for inland
areas. Coastal and valley areas will also be warmer today. Slight
deepening of the marine layer is possible for Wednesday and
Thursday which would bring slight cooling into coastal and valley
areas.

There`s a weak coastal eddy early this morning with stratus along
the Baja coast extending northward along the coasts of San Diego
and Orange Counties. Higher resolution models show a weak coastal
eddy continuing at times through Wednesday and Thursday. Coastal
low clouds will spread slightly farther inland each night, into
the western valleys for Thursday night into Friday morning. As
high pressure aloft strengthens the marine inversion, clearing
near the coast could be slow or limited for the next few
afternoons.

&&

.LONG TERM (Friday through Monday)...
A closed low pressure system off the California coast to the west
of San Diego on Friday will move slowly eastward. The GFS and
ECMWF ensembles are similar on timing in moving the trough axis
across southern California on Sunday night. This will bring cooling
of a few degrees per day for Friday and Saturday with greater
cooling for Sunday into Monday. Stronger onshore flow will bring
periods of stronger and gusty west winds in the mountains and
deserts with the strongest winds for late Sunday into early
Monday with the trough passage. The low pressure system will also
deepen the marine layer onto the coastal mountain slopes and bring
a slight chance for light showers for late Sunday into early
Monday.

&&

.AVIATION...
230900Z...Coast...Areas of coastal low clouds will continue to
form through sunrise. Bases will be around 1000-1200 feet MSL with
tops to 2000 feet. Local vis 2-4 miles will occur over higher
coastal terrain and in the coastal valleys. Clearing of low clouds
expected by 15-17Z. Areas of coastal clouds to gradually develop
after 06Z tonight and into Wednesday. Bases would be a little
lower...800-1000 feet MSL. Otherwise, mostly clear skies today and
tonight.

Mountains/Deserts/Valleys...Areas of N/NE surface winds 20-30 knots
with local gusts 35-45 knots will occur mainly on southern slopes of
the San Gabriel/San Bernardino Mountains and far northern Coachella
Valley through 19Z. Mostly clear skies today and tonight.

&&

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

&&

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

&&

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

&&

$$

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


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