Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
230 am PDT Tuesday Apr 28 2015
Synopsis...high pressure will keep the weather warm and dry much of
the week. Afternoon sea breezes will keep the days more moderate
along the coast...but temperatures will still be well above average.
The onshore flow will increase later in the week...building the
marine layer and associated coastal clouds...fog...and cooler days.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
A cloudless night will be followed by a sunny warm day today. For
areas near the coast it will be likely the warmest day in the coming
week. A high pressure ridge over California has brought US the warm
weather. We still have a touch of the offshore flow this morning but
no more strong Santa Ana winds. It will continue quite dry except at
the beaches as we slowly transition to neutral flow and then weak
onshore flow. A big low cloud deck has smothered the central coast
and is trying to turn the corner at Point Conception into The
Channel islands. This might otherwise portend a quick return of
coastal clouds and fog for Southern California...but our best
guidance keeps the onshore flow rather weak or even neutral over US
through Wednesday. So it will take some time for a decent marine
layer to develop and bring back the coastal clouds. Right now we
expect Wednesday night for their reappearance. The high pressure
ridge will lean over under a weak amorphous trough that bears down
over the West Coast Wednesday through the weekend. The changes will
be subtle and gradual. For Wednesday into Friday there will be a
cooling trend at the coast beginning and nosing a little farther
inland each day. That will mean mountains and deserts will not start
cooling until about Friday. A very weak shortwave out west in the
Pacific gets picked up by the weak West Coast trough and moves
through northern Baja California California around Monday. There is limited
moisture entrainment into our region with this feature so no real
chance of rain is manifest. The marine layer GOES deep however for a
more accelerated clouding and cooling trend next week.
Aviation... 280900z...a few patches of low clouds and fog may form
over the coastal waters by this evening but are not expected to
reach the coastal airports. Otherwise a few high clouds and
unrestricted visible through Wednesday morning.
Marine... 205 am...no hazardous marine weather expected through
Beaches... 215 am...a powerful storm over the southeast Pacific
with a large fetch of 50 knots winds has generated combined seas of
over 50 feet. While most of the swell energy will move into central
and South America...south-southwest swells of 4-5 feet with a 20-22
second period are forecast to reach the Southern California beaches
late this weekend into early next week. This will likely generate
large and potentially damaging surf and very strong rip currents
along the Orange and San Diego County beaches as the swell peaks
Sunday and Monday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.