Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 221635
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
935 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...

...Update...

The sky is mostly clear this morning. Just a few high clouds out
there. Over the ocean, it is mostly clear as well though there is
patchy low stratus just off the Orange County coast. The stratus
off the San Diego coast has dissipated. So a sunny, warm day is
expected, except cool at the coast with patchy stratus possible.
The coastal stratus likely will increase in coverage tonight
along with a potential of patchy fog. See previous discussion
below for further forecast details.

...Previous Discussion (Issued at 403 AM PDT Sun Apr 22 2018)...

.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 ECMWF slower and farther north with the 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...
221630Z...Coast...Patchy low clouds and fog could return to some
beaches as early as 18Z but impacts at coastal TAF sites are
unlikely at that time. Low clouds could begin to increase in
coverage and spread inland around 03Z Mon, but timing is uncertain.
Expect cloud bases 400-800 ft MSL and areas of vis below 3 SM
extending up to 5 miles inland by 12Z Mon. Vis of 1 mile or less
will be possible on higher coastal terrain. Otherwise, FEW-SCT
clouds at/above 25000 ft MSL through late tonight.

Valleys/Mountains/Deserts...FEW-SCT clouds at/above 25000 ft MSL
with unrestricted vis through late tonight.

&&

.MARINE...
Patchy fog may develop over the coastal waters each morning through
Wednesday. 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...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...Gregoria (Update)/17 (Prev Discussion)
AVIATION/MARINE...PG



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