Scientific Forecaster Discussion
Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
915 PM PST Friday Nov 21 2014
a windy weather pattern will develop across southwest California
this weekend as a weak low pressure system moves across the state
and high pressure builds off the coast. Offshore winds are expected
Sunday through Wednesday with warmer and drier weather next
week...then slight cooling by Thanksgiving day.
Short term (tonight-mon)...mostly clear skies with some hi clouds
at times covered much of the forecast area this evening. There were
clouds banked upon the north slopes this evening which should continue
overnight. Low clouds over the southern San Joaquin Valley are expected
to move into the slo County interior valleys overnight thanks to an
easterly low level flow across this area. Clouds are also expected
to thicken over the rest of slo County and also across northern sba
County overnight as an upper level disturbance approaches the area.
Further S...it looks like fair skies with some hi clouds will
prevail through the night. There were gusty northwest to North Canyon winds noted
across the sba County mountains and sba County S coast this evening
thanks to a strong northerly pressure gradient (at 03z -4.0 mb
sba-smx and -5.5 mb sba-bfl). Gusts up to 40 miles per hour have been noted
already...and the winds should increase a bit further overnight with
gusts up to 50 miles per hour possible in the favored areas. As a result...a
Wind Advisory is in effect for this area overnight. Some gusty west to
north winds will also affect the l.A./Vtu mountains and parts of the Antelope
Upper level ridging will prevail over southwestern California tonight through Sat.
Upper ridging will linger off the California coast Sat night and sun...then
build back toward the region Sun night and Monday. A weak upper level
disturbance is forecast to move into slo/sba counties Sat with a
slight chance to chance of showers...then the slight chance of
showers will spread into the North Mountain slopes for Sat night. This will
be a weak weather system with scattered light amounts of precipitation. Gusty
northwest to north winds are expected for the l.A./Vtu mountains at times Sat through
Sun morning...and spread into the Antelope Valley. Wind gusts to
warning levels are possible in the mountains where a high wand watch
was issued...and advisory level winds are expected for the Antelope
Valley where a Wind Advisory is in effect. In addition...strong and
gusty north winds are expected Sat night for the sba County mountains and S
coast...where a high wind watch is also in effect. Please see the
latest non-precipitation weather message (laxnpwlox) for details on
the wind advisories and high wind watches. The flow is expected to
turn more northeast by later Sun morning and continue through
Monday...with gusty winds below and through the favored passes and canyons
likely to advisory levels in many areas. There should be mostly
cloudy skies for slo/sba counties and the North Mountain slopes of vtu County
Sat into Sat evening...with partly cloudy skies elsewhere. Clearing
skies should then develop over the forecast area on sun thanks to
the drying offshore flow. Mostly clear skies will then continue through
Monday in all areas. Temperatures on Sat will remain slightly below normal...
then turn milder and closer to normal mainly west of the mountains on
sun...and to several degrees above normal on Monday...while temperatures
continue slightly below normal to near normal for the mountains and
***From previous discussion***
Long term (tue-fri)...Tuesday is likely to be the warmest and
driest days of the week. A high pressure ridge over the eastern
Pacific will shift inland by Wednesday. This would swing winds back
to onshore across coastal areas late in the day with slightly cooler
temperatures. Then southwest flow aloft builds to our west in
advance of the next storm system to move into California late Friday. Expect
a cooling trend Thursday and Friday with potential for morning low
clouds at the beaches. A weak cold front may approach the central
coast Friday...but at this time precipitation does not look
favorable so have left it out of the forecast.
At 2330z...there was no marine inversion at klax.
Generally hi confidence overall in the 00z tafs. VFR conditions are
expected at most of the airfields through Sat. For kprb...there is
moderate confidence of MVFR ceilings 10z-16z...otherwise generally hi
confidence in the 00z taf with VFR conditions through Sat. For ksbp and
ksmx...there is generally hi confidence in the 00z taf. VFR
conditions are expected through most of the taf period...with MVFR ceilings
possible after 23z Sat. There is...however...a 10-20 percent chance of
intermittent MVFR ceilings at these airfields from about 14z-20z Sat.
Low level wind shear is expected at ksba through 12z Sat due to gusty North
Canyon winds in the vicinity. There will be gusty west to northwest winds at
kpmd and kwjf this evening and again by late Sat morning through the
Klax...hi confidence in the 00z taf with VFR conditions expected at
the airfield through Sat evening. Light north to east flow is expected tonight
into Sat morning.
Kbur...hi confidence in the 00z taf with VFR conditions expected at
the airfield through Sat afternoon. North winds to around 10 knots are
possible at the airfield 16z-22z Sat.
Marine...21/800 PM PST...
it is likely Small Craft Advisory conditions will persist over the
outer waters from Point Sal to San Clemente Island through late Sat
night. There is a chance Small Craft Advisory conditions will develop near shore from
Ventura Harbor to Santa Monica and extend out to Santa Cruz Island
Sunday morning. Seas generated over the eastern Pacific within
290-300 degrees relative to the area will arrive Sunday and create
Small Craft Advisory conditions for hazardous seas along the central coast and
extending south to San Clemente Island.
Fire...21/320 PM PST.
Strong northwest to north flow will form late Saturday afternoon and
night...affecting the I-5 corridor and Antelope Valley...as well as
southern Santa Barbara County. Sustained winds to 40 miles per hour and gusts
to 60 miles per hour are possible in these areas. The winds will shift to a
northeasterly direction by Sunday afternoon and weaken some through
Monday...but will remain gusty through Wednesday with winds
generally 15 to 30 miles per hour with gusts to 45 miles per hour.
Meanwhile...dry air aloft will impact the mountains late Saturday
night and Sunday...then drop into the valleys and coasts Sunday
night and Monday. Minimum humidities with this dry air should
generally be in the 8 to 15 percent range. As a result...red flag
conditions are possible with this event. The Santa Ynez and San
Rafael ranges of Santa Barbara County...including the Montecito
area...have a chance for early Sunday morning...and a Fire Weather
Watch has been issued. The mountains of Los Angeles and Ventura
counties may see isolated red flag conditions on Sunday. More
widespread red flag conditions are possible on Monday...and even
more so on Tuesday through Wednesday over much of Los Angeles and
Ventura counties. Additional fire weather watches may be issued over
the weekend to address this period. Santa Barbara and San Luis
Obispo County will see elevated fire concerns Sunday through Monday
with breezy northeast winds...but should not reach red flag
high wind watch (see laxnpwlox).
Fire Weather Watch (see laxrfwlox).
Wind Advisory (see laxnpwlox).
Small Craft Advisory (see laxmwwlox).
High rip current risk (see laxsrflox).