Scientific Forecaster Discussion
Southwest California area forecast discussion...updated
National Weather Service Los Angeles/Oxnard California
440 am PDT Tuesday Sep 23 2014
Updated aviation section
Building high pressure will bring a warming trend through middle week.
A trough of low pressure will then bring cooler weather and an
increase in night through morning low clouds and fog for late in the
week. Offshore flow and a warming trend are possible by next Sunday.
Short term (today-thu)...
the marine layer is 700 feet deep and the onshore flow is quite
weak. Marine layer stratus currently only affect western sba County
including the Santa Ynez Valley. There are some low clouds forming in
the Santa Monica basin so the l.A. County coast will likely see some
patchy morning low clouds. Today will be sunny and warmer as a 592
dm upper high over Yuma will bring higher heights and the weak onshore
push will allow for a later sea breeze.
It will be hard to tell Wednesday apart from today. Maximum temperatures may
rise a degree as the gradients trend every so slightly more
offshore. There may be a little better morning cloud coverage over
southern l.A. County...but otherwise little change.
A large early season Pacific northwest storm sets up shop a couple of hundred
miles west of Vancouver Island. It will whip a cold front into
Washington...Oregon and northern cal Wednesday night and Thursday. The front
will die on the vine south of the Bay area and the chance of rain will
end around Monterrey. Sill low will bring a deeper marine layer.
Skies will turn partly cloudy as some middle level clouds stream over
the area ahead of the front. Heights will drop through the day. Maximum
temperatures will drop 5 to 15 degrees with the biggest drops north of
Long term (fri-mon)...
the trough will sit nearly stationary off of the West Coast Friday and
Sat, the lower heights and broad cyclonic flow will trigger a deep
marine layer that will bring low clouds to all of the coasts and
valleys and may even climb up the coastal slopes. Cant rule out some
local drizzle during the morning especially near the foothills. Maximum temperatures
will fall each day and Saturday will be the coolest of the next 7.
The low will exit the area Sunday and dry northwest flow will set up in its
place. Rising heights will smoosh the marine layer some and will kick
up temperatures some. There are some hints of (weak) offshore flow setting
up Monday and this will further shrink the marine layer as well as
continue the warming trend.
Areas of low clouds and fog with IFR to LIFR conds will affect the
central coast through middle to late morning. S of pt Conception...
stratus will be more patchy in nature...but still expect occasional low
MVFR to high IFR conds in areas near the coast through middle morning.
Expect widespread low clouds/fog with IFR to low MVFR conds on the
central coast...in the Santa Ynez Valley...and across coastal
sections of l.A. County late tonight/Wednesday morning.
Klax...low to moderate confidence in the 12z taf. There is a 30
percent chance that conds will remain VFR this morning.
Kbur...high confidence in the 12z taf with VFR conditions
expected through the period.
Across the southern two thirds of the outer waters...high confidence
in low-end Small Craft Advisory winds through late tonight. Only
moderate confidence in Small Craft Advisory conds across the
northern third of the outer waters (north and west of point sal).
Across the inner waters...high confidence in conds remaining below
Small Craft Advisory levels through Friday.
A large long-period northwest swell will move into the coastal
waters Wednesday night...peak on Thursday then linger through
Small Craft Advisory (see laxmwwlox).