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Area forecast discussion
National Weather Service San Diego California
403 am PDT sun Apr 22 2018

Synopsis...
high pressure aloft and weak onshore flow will bring warmer
weather through Monday with a gradual return of night and morning
coastal low clouds and fog. For Tuesday through Friday, a low
pressure system off the West Coast will begin to move towards the
Pacific northwest late in the week. This will slowly strengthen
onshore flow across Southern California and bring slow deepening
of the marine layer. Areas of night and morning coastal low clouds
and fog will spread into portions of the valleys with a cooling
trend spreading into the valleys.

&&

Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...

Short term (today through tuesday)...
early this morning...a weak low pressure system is moving into
northern baja with a few high clouds extending into Southern
California. Stratus coverage is still quite limited with a narrow
band of stratus just off the northern Baja Coast extending
northward just off coast of San Diego and Orange counties with
the coverage much patchier off the Southern California coast.
Coverage may increase a little just off the Southern California
coast early this morning and may spread locally inland after
sunrise. With the marine inversion near 600 feet...locally dense
fog is possible near the coast. Greater coastal stratus coverage
is expected for tonight into Monday morning along with slight
deepening of the marine layer. Locally dense fog is possible from
the coast inland to around The Mesas. A little more deepening of
the marine layer for Monday night into Tuesday morning should
allow the stratus to extend into portions of the western valleys
for late Monday night into Tuesday morning.



Coastal and valley areas will remain warmer today with slow
cooling beginning to spread into the valleys on Monday and
Tuesday. Inland areas will be a few degrees warmer for today than
Saturday with similar high temperatures expected for Monday and
Tuesday.

&&

Long term (wednesday through saturday)...
a low pressure system off the West Coast will move slowly towards
the Pacific northwest with the GFS farther south and a little
faster and the European model (ecmwf) slower and farther north with the European model (ecmwf)
ensemble mean in between and favored for now. Onshore flow will
strengthen with slow cooling for inland areas for Wednesday
through Saturday with periods of gusty southwest to west winds in
the mountains and deserts. The marine layer will slowly deepen
with slow cooling spreading into the valleys and with areas of
night and morning coastal low clouds and fog spreading farther
into the valleys.

&&

Aviation...
220945z...coast...patchy low clouds with bases 300-700 ft mean sea level and
vis 3 sm or less possibly forming within 5 miles of the coast
through 16z. Confidence is low that any cigs will reach the
coastal airports. Otherwise few-scattered clouds at/above 25000 ft mean sea level
through late tonight. More widespread low clouds with bases
400-800 ft mean sea level and areas of vis below 3 sm developing along the
coast and up to 5 miles inland after 23/03z.

Valleys/mountains/deserts...few-sct clouds at/above 25000 ft mean sea level
through late tonight and unrestricted vis.

&&

Marine...
patchy fog may develop over the coastal waters each morning through
Tuesday. Otherwise no hazardous marine weather is expected through
Thursday.

&&

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

&&

Sgx watches/warnings/advisories...
California...none.
Pz...none.

&&

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