Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
500 am PDT sun Mar 16 2014
..updated aviation...Marine and fire discussions...
upper level high pressure and weak offshore flow will make for
another very warm day across the region. Significant cooling is
expected on Monday as an upper trough moves into the West Coast. A
round of gusty winds will likely affect portions of the region
Monday night and Tuesday behind a dry frontal system. Additional
cooling is likely during the middle and end of the week...with
daytime temperatures down to near normal levels in most areas.
Short term (today-tue)...clear skies across the entire region this
morning. Pressure gradients were weakly offshore. Some gusty NE winds
will affect the mountains and valleys of l.A. And vtu counties...and
possibly the vtu County coastal plain...but winds will remain well
below advisory levels. With the weak offshore flow and additional
warming at 850 and 950 mb...there may be a couple of degrees of
warming in most areas today...with temperatures possibly rising to or just
above 90 degrees in the valleys...and possibly across interior sections
of the coastal plain. Maximum temperatures will be tricky near the coast
today...since gradients flip onshore by afternoon. At this
point...feel that temperatures in most beach areas will reach at least 80
degrees this morning. If the seabreezes arrive sooner than
expected...highs will stay in the 70s near the beaches.
The upper high will weaken and move southward tonight and Monday as
a broad trough moves through the Pacific northwest and into the Great Basin.
Onshore gradients will increase on Monday. There should be
significant cooling in most areas on Monday...with maximum temperatures down as
much as 10 to 15 degrees from those reached today in coastal and
many valley areas. Strong west winds should reach advisory levels in
the Antelope Valley Monday afternoon and evening.
The WRF continues to show a tightening north-S pressure gradient Monday
night...with gusty north winds likely approaching advisory levels
across the Santa Ynez range and through the i5 corridor. Some
stratus may push into the central coast and coastal sections of
l.A. And possibly vtu counties Monday night/Tuesday morning. If the
forecast eddy circulation is a big stronger than expected...clouds
could push into the l.A. County valleys...especially the San Gabriel
valley. Low level flow will turn quickly northeasterly Tuesday morning as west-east
gradients become moderately offshore. There will likely be some
gusty winds in the mountains and valleys of l.A. And vtu counties
Tuesday...possibly spreading into the vtu County coastal plain.
Any clouds near the coast should vanish quickly Tuesday morning.
There will be cooling in the mountains and deserts on Tuesday as
heights/thicknesses continue to fall...as do temperatures at 850 mb. West of
the mountains...the downsloping offshore flow should offset cooling...so
expect little change in maximum temperatures...and possibly even slight warming
in some coastal areas.
Long term (wed-sat)...offshore gradients Wednesday morning should keep
skies mostly clear across most of the region...save portions of the
central coast and coastal sections of l.A. County where some low
clouds are possible late Tuesday night/Wednesday morning. While
heights/thicknesses actually rise on Wednesday...onshore flow will
increase. This should offset any warming west of the mountains...so
expect maximum temperatures to be about the same as on Tuesday. There could be a
couple of degrees of warming in the mountains and deserts. A broad trough
will set up along or just off the West Coast Thursday and linger through
Sat. Expect night through morning low clouds in coastal and most
valley areas Thursday through Sat...with maximum temperatures near or possibly even
slightly below normal.
high confidence with 12z tafs over next 24
hours. 20 percent chance for LIFR/IFR ceilings near klgb/klax after 10z
Monday morning and ksmx after 09z Monday morning.
Klax...hi confidence with 12z tafs...except 20 percent for LIFR/IFR
conds between 10z-16z Monday morning.
Kbur...hi confidence for ceiling and visibility unlimited conds with 12z tafs over next 24
Gale Warning now in effect from pt Piedras Blancas to San Clemente
Island early Monday morning through Tuesday morning. The western
portion of the Santa Barbara Channel will be included as well later
Monday afternoon through early Tuesday morning. A strong 1035 mb
surface high will build in across the northern portion of the outer
waters with a 1004 mb low expected in the Lower Desert. This will
create a strong gradient allowing gale force northwest winds to develop by
Monday morning and continue through early Tuesday morning.
The seas generated by the strong northwest winds will create hazards
along west and northwest facing shores and in exposed bays and
inlets of the northern Channel Islands as well as Santa Barbara and
san nicolas islands Monday through Tuesday.
A storm system over the western portion of the central Pacific had
generated seas over 30 feet. A long period 300-290 degree
groundswell will arrive along the central coast this morning and
persist through Tuesday. A high surf advisory is in effect for the
central coast today through Tuesday. This surf event will likely
generate strong rip currents but on Monday the rip currents will be
frequent and widespread from slo to la counties. Later shifts will
need to look closely to see if Ventura County beaches might need a
high surf advisory as well...where the Los Angeles beaches main
issue will be high rip current risk.
many inland areas will see humidities fall to between 7 and 12
percent today. The combination of locally breezy offshore winds
with very warm and dry conditions will continue to bring elevated
fire danger today...with brief critical fire weather conditions
possible. An earlier and more pronounced sea breeze is expected to
arrive across coastal areas early this afternoon...overspreading
the valleys between 2 and 5 PM. As a result...a pronounced wind
shift is expected across lower elevations this afternoon with
continued warm and dry conditions...resulting in a continuation of
elevated fire concerns.
Gale Warning (see laxmwwlox).
Small Craft Advisory (see laxmwwlox).
High surf advisory (see laxcfwlox).
High rip current risk (see laxsrflox).