Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 051158
Area Forecast Discussion
National Weather Service San Diego CA
358 AM PST Mon Dec 5 2016
A low pressure system moving inland through the western states
will bring stronger onshore flow across Southern California
through Tuesday with cooling...a return and deepening of the
marine layer with areas of night and morning spreading on the
lower coastal mountain slopes on Tuesday...and gusty west winds in
the mountains and deserts. For Wednesday and Thursday...weak high
pressure aloft near the West Coast and weak surface high pressure
over the Great Basin will bring warming and locally gusty
northeast winds near the coastal foothills. Towards next
weekend...another low pressure system developing near the West
Coast will bring cooling...a return of the marine layer with areas
of night and morning coastal low clouds and fog....and gusty west
winds in the mountains and deserts.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
A trough of low pressure will move inland through the western
states bringing stronger onshore flow across Southern California
through Tuesday. Cooling of high temperatures will spread inland
through Tuesday and Wednesday. High temperatures will fall to
around 5 degrees below average for some inland areas.
The stronger onshore flow will bring gusty west winds to the
mountains and deserts for Tuesday afternoon and evening...but with
winds mostly remaining just below advisory strength.
A coastal eddy has developed with areas of stratus off the
northern Baja coast extending northward into portions of coastal
Southern California...but with patchier coverage. The marine layer
has been deepening overnight with improving visibilities near the
coast in Orange and San Diego Counties. Additional deepening
is expected to push the low clouds onto the lower coastal
mountain slopes late tonight into Tuesday. Some patchy drizzle or
a few sprinkles toward the coastal foothills is not out of the
question for late tonight into Tuesday morning...but little or no
measurable precipitation is expected.
For Wednesday and Thursday...weak high pressure near the West
Coast and weak surface high pressure over the Great Basin will
bring a warming trend with warming to near average high
temperatures on Thursday. There will be locally gusty northeast
winds near the coastal foothills at times and below passes and
canyons...but with winds mostly remaining below advisory strength.
Toward next weekend...broad weak upper troughing will develop
near the West Coast bringing a return of onshore flow to Southern
California. This will bring a cooling trend and a return of the
marine layer with areas of night and morning coastal low clouds
and patchy fog. There will also be gusty west winds in the
mountains and deserts. It is possible that trough of low pressure
could have enough amplitude combined with a plume of subtropical
moisture to bring some light precipitation for Southern California
around Sunday. For now...the forecast remains dry.
051000Z...Coastal low clouds and fog will continue through 17Z this
morning. Bases will be around 400-800 feet msl with areas of vis 3-
5SM. Low clouds will redevelop at around 1000 feet after 03Z tonight
and spread farther inland overnight. Otherwise, variable thin high
clouds and VFR conditions today and tonight.
No hazardous marine weather is expected today through Friday.
Onshore flow and deepening of the marine layer will bring a
recovery of humidities through Tuesday. For Wednesday into
Thursday...weak high pressure aloft near the West Coast and weak
surface high pressure over the Great Basin will bring
warming...gusty northeast winds near the coastal foothills and
below passes and canyons...and lower inland humidities. Winds are
expected to be a little stronger on Wednesday...with humidities
lowest and temperatures warmest on Thursday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.