Scientific Forecaster Discussion
fxus66 klox 241137
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
337 am PST Fri Nov 24 2017
record temperatures in the deserts and above normal temperatures
inland are forecast into Friday as the high will weaken. A low
will arrive Sunday for possible precipitation from Santa Barbara
and northward, that should spread to Los Angeles mountains by that
night and into Monday. Then a high should build into the Great
Basin late Monday into early Wednesday for gusty offshore winds
and a warming trend.
Yesterday was the hottest Thanksgiving day ever in downtown Los
Angeles, where the 92 degree high eclipsed both the Thanksgiving
day record of 90 degrees set on November 26, 1903, and the daily
record for the 23rd of 91 degrees, set in 1933.
Two days of similar weather on tap courtesy of an upper level
ridge to the south and offshore flow. The ridge is weaker than it
was ydy and will weaken further tomorrow with 500 mb hgts moving
from 590 dm to 586 dm. The offshore flow will also weaken as the
cold sfc high moves eastward. Max temps will generally fall 3 to
6 degrees each day. Todays highs will be 12 to 16 degrees above
normal and saturdays will be 8 to 12 degrees. The ridge is keeping
a river of mid and high level clouds to the north but
occasionally some of these clouds will break through the ridge and
The weather changes Saturday night as the ridge is pushed to the
east by a cold Gulf of Alaska low moves into the pac northwest. A trof
associated with this low will approach the central coast. There is
a chc the weak lift associated with the trof coupled with the
onshore trends will probably (although by no means certain)
create some marine layer clouds across the la and vta County
On Sunday a little upper low pinches off from the base of the trof
west of the Bay area and begins to move to the east. Clouds will
increase esp over slo and sba counties. A chc of rain will develop
over the coast and coastal foothills of slo County. Max temps will
drop across the area...but mostly across slo and sba counties
where Max temps will drop 5 to 10 degrees and will be near
seasonal norms. The Max temps for vta and la counties will drop 2
to 4 degrees and will remain 4 to 8 degrees above normal.
Rain will likely develop across the slo County coast Sunday night
as the upper low drives into the Bay area. There is a good chc of
rain over the rest of slo and sba County as well as the trof moves
through those counties. In fact if 12z are in as good agreement as
the 06z runs are pops across both slo and sba counties will be
raised into the likely categories.
This system could bring a quarter inch to a half inch of rain to
the central coast with lesser amounts across the interior.
The trof will weaken and move through the area on Monday. A chc of
rain will continue over slo and sba counties as well as vta
County Monday morning. The trof will exit in the afternoon but a
chc of rain will persist across most of the interior sections
bordering on Kern County. Skies will be mostly cloudy and there
will be onshore flow. Max temps will fall slightly across slo and
sba counties but Max temps will plummet 8 to 16 degrees across vta
and la counties where Max temps will end up 3 to 6 degrees blo
The ec and GFS have really changed their tune for the Tuesday
through Thursday forecast. Where there once was strong offshore
flow on Tuesday and Wednesday now there is weak-moderate offshore
flow. Max temps will rebound about 10 degrees on Tuesday and will
change little Wednesday.
Current mdls show the strong offshore flow now developing on
Thursday morning. But given the big change from ydy's mdls would
not place too much confidence in this solution.
At 10z there was no real marine inversion as klax.
Expect clear skies and VFR conds across the region through the pd.
There is a 20% chance of MVFR vsbys in haze after 09z tonight.
Klax...high confidence in the 12z taf. There is a 20 percent
chance of MVFR haze between 09z and 17z Sat.
Kbur...very high confidence in the 12z taf with VFR conds through
Moderate to high confidence in current forecast for the northern
two thirds of the outer waters, with Small Craft Advisory conditions expected
to continue through late tonight. Lower confidence in the
forecast for the southern outer waters. There is a 30-40% chance
that a Small Craft Advisory will be needed this afternoon and evening. Expect Small Craft Advisory
level winds across most of the outer waters Sun night through Tue.
For the inner waters north of pt Conception, moderate to high
confidence in current forecast. Winds and seas are expected to
remain below Small Craft Advisory levels through Sunday although there is a 20%
chance of Small Craft Advisory level winds this afternoon/evening. On Monday,
there is a good chance of Small Craft Advisory level winds.
For the waters south of Point Conception, winds and seas will
remain below Small Craft Advisory levels through Sunday evening. For Sunday night
and Monday, there is a 50% chance of Small Craft Advisory level winds, especially
across western sections.
Pz...Small Craft Advisory in effect until 3 am PST Saturday for
zones 670-673. (See laxmwwlox).
Hazard potential outlook...(sun-thu)
there is the potential for elevated to critical fire weather
conditions Monday through Wednesday for portions of southwest
California. From Monday into Monday night, there is the potential
for strong northerly winds, followed by the potential for
strong Santa Ana winds and low humidities on Tuesday, with gusty
offshore winds lingering into Wednesday.