Area forecast discussion
National Weather Service San Diego California
300 am PDT Wednesday may 22 2013
Synopsis...
low pressure will bring cooler weather with more extensive coastal
clouds for the next several days. Locally strong and gusty winds are
expected through mountain passes and into adjacent deserts as
well...but will be strongest today and Thursday during afternoons
and evenings. The cooler weather will continue with night and
morning low clouds and fog throughout most of the coastal basin
through early next week.
&&
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
counties...
The marine layer has deepened in response to a low pressure trough
approaching from the north and a continuing coastal eddy. As a
result the low clouds have already filled most of the inland
valleys. However...the extent of the low cloud deck off the coast is
not impressive. With cooler air coming the marine inversion will
weaken and allow for decent clearing in all areas today. The low
clouds will gather and head inland quite early as the low pressure
trough over California maxes out its amplification over the state.
That will bring our deepest marine layer along with spotty drizzle
late tonight and early Thursday. The clouds could pull a reverse
clearing pattern Thursday with the coast clearing before inland
areas...especially the coastal foothills. Onshore pressure gradients
will produce pockets of strong winds in the mountains and deserts
this afternoon through the evening. With little contribution from
winds aloft these winds will be mainly driven by surface pressure
gradients. And so they will be localized and strongest through and
just to the Lee of mountain passes and into the deserts. The same
will be true Thursday afternoon and evening. The low pressure trough
along the West Coast backs off a little Friday but continues for a
long while. It keeps getting reinforced by shortwaves that rotate
through the mean cyclonic flow over the weekend. We will continue
with slightly cooler than normal weather with a deeper than normal
marine layer. Overall fairly seasonal weather. One shortwave in
particular arrives next Monday (gfs model) or Tuesday (euro model).
It looks stronger...something that would deepen the marine layer and
produce drizzle...and stronger wind in the mountains and deserts. We
will lean that direction in the forecast. What happens beyond
Tuesday is either a strong jet stream heading into California with
wind and possible showers (gfs)...or a pretty decent ridge of high
pressure and very warm weather (euro).
&&
Aviation...
220910z...coast/valleys...stratus with bases around 1400-1800 feet mean sea level
will continue to fill into the inland valleys this morning. 3-5 sm
visibility in br/haze possible in the inland valleys. Stratus will clear 15
to 17z inland and 16 to 18z near the coast. Stratus will move back
into the coastal airports 00-04z...spreading into the lower coastal
slopes of the mountains overnight. Bases will be around 1500-2000 feet mean sea level.
Mtns/deserts...otherwise...mostly clear with unrestricted visible
through Thursday morning. West winds with surface gusts to 40 knots will develop
over the mountains and deserts this afternoon and evening...weakening
tonight.
&&
Marine...
a 3 feet...16 second period period southwest swell will continue surf of
3-5 feet and the potential for strong rip currents. A 6-8 feet
short-period northwest swell will move into the outer coastal waters
this afternoon through Thursday resulting in rough seas near San
Clemente Island and a slight increase in surf along exposed west
facing beaches.
Swell and surf will gradually subside Friday through the weekend.
&&
Sgx watches/warnings/advisories...
Wind Advisory from 4 PM today until 2 am Thursday for areas of the
mountains and deserts.
&&
$$
Public...mm
aviation/marine...sunset
