Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 221100
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
400 AM PDT Mon May 22 2017

.SYNOPSIS...
High pressure aloft will continue the slow warming trend for
inland areas through Tuesday. For coastal and valley areas...weak
onshore flow will bring slow deepening of the marine layer with
areas of night and morning low clouds and fog extending a little
farther inland each night with slow cooling spreading inland.
Cooling will spread farther inland on Wednesday as high pressure
aloft begins to weaken. For Thursday and Friday...a trough of low
pressure will bring stronger onshore flow with strong gusty west
winds in the mountains and deserts. Cooling will take high
temperatures to around 10 degrees below average for Friday. The
marine layer will deepen into the inland valleys on Thursday and
onto the coastal mountain slopes with a few light showers possible
from the coast to the coastal slopes late Thursday night into
Friday morning. High pressure aloft will bring an inland warming
trend for the holiday weekend with areas of night and morning low
clouds and fog for coastal areas.

&&

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

.SHORT TERM (Today through Wednesday)...
Early this morning...satellite imagery shows widespread stratus
over the coastal waters extending inland to far inland Orange
County and near the mesas in San Diego. It may spread into the far
western valleys around sunrise. The marine layer is near 1000 feet
deep with lowest visibilities mostly near the mesas in San Diego
County. Continued slow deepening of the marine layer is expected
to take the low clouds a little farther inland into the valleys
for Tuesday and Wednesday.

High pressure aloft will continue the inland warming trend through
Tuesday with Tuesday expected to be the warmest day for the
deserts...mountains...and far inland valleys. This will elevate
the heat risk in the lower deserts for today into Tuesday.
High pressure aloft will begin to weaken on Wednesday with slow
cooling spreading farther inland.

&&

.LONG TERM (Thursday through Sunday)...
A trough of low pressure over the western states will bring
stronger onshore flow for Thursday and Friday. Periods of strong
gusty winds are expected for the mountains and deserts and could
be near advisory strength at times. Greater cooling will spread
inland with high temperatures for inland areas around 10 degrees
below average on Friday. The marine layer will deepen enough for
coastal low cloud and fog to extend into the inland valleys for
late Wednesday night into Thursday morning with continued
deepening taking it onto the coastal mountain slopes Thursday
night into Friday morning. The lower resolution global models
along with the 6-km local workstation WRF with GFS boundary
conditions all show light precipitation from the coast waters
inland to the coastal mountain slopes for late Thursday night into
Friday morning. A slight chance of showers has been added to the
forecast for this time period...but any rainfall is expected to be
light.

For next weekend...high pressure aloft will return along the West
Coast bringing a warming trend for inland areas with high
temperatures warming to a few degrees above average by Memorial
Day. Areas of night and morning low clouds and the marine layer
will keep high temperatures near the coast near average.

&&

.AVIATION...
220900...Clear skies today and tonight except near the coast.
Coastal clouds and fog will continue through about 16-17Z. Bases
will be around 600-800 feet msl with tops to 1500 feet. Vis 2-5sm at
times on the coastal mesas, but locally lower along inland edge of
clouds. Coastal low clouds with similar bases and extent are
expected to move ashore after 05Z this evening.

&&

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

&&

.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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