Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 231147
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
347 AM PST Thu Nov 23 2017

.SYNOPSIS...
Record or near record temperatures are forecast to continue
through Friday as the strong upper ridge and weak offshore flow
continues to persist over the region. An area of low pressure
will approach by Sunday with increasing clouds and cooler
temperatures. There is a chance of showers for areas north of
Point Conception Sunday night into Monday. Surface high pressure
will build into the Great Basin early next week allowing for
gusty offshore winds to develop by late Monday through early
Wednesday.

&&

.SHORT TERM...(TDY-SAT)

High pressure continues to dominate the Southern California
weather pattern. Currently 592 DM hights are over the area
extending from an upper high 250 miles SW of San Diego. There is
about 4 MB of an offshore push both from the East and North. There
are slight onshore trends. The upper ridge will keep the clouds
out of VTA and LA counties but SLO and SBA counties will have
enough mid and high level clouds to make for a partly cloudy day.
All of this is going to add up to a very warm day. One of the
warmest if not the warmest Thanksgiving since records started back
in the 1870s. Many daily records are poised to fall esp in the
vlys. Still it will be cooler (esp at the coast) than ydy as hgts
will fall and the offshore flow will weaken through the day as a
trof moves into Nrn CA.

The highest temperature ever recorded on Thanksgiving (which is
not the same a daily record since it falls on different dates) in
Downtown Los Angeles was 90 degrees, set on November 26th, 1903.

The upper level ridge of high pressure will continue to weaken
Friday into Saturday. The offshore flow will also decrease some
each day. Periodic higher level clouds will drift across the
forecast area, while temperatures will continue to gradually trend
downward.

Max temps however will still be well above each day...today temps
will be 18 to 22 degrees above normal...12 to 18 degrees above
normal on Friday and 8 to 12 degrees on Saturday.

.LONG TERM...(SUN-WED)

A stronger upper low moves into Pac NW on Sunday and pushes the
ridge away to the south and east. A weak cold front will approach
the area Sunday afternoon. Clouds will increase through the day
esp over SLO and SBA counties. A slight chc of rain will develop
over NW SLO county later in the afternoon. There will be an
increasing chc of rain Saturday night into early Sunday morning
across SLO and SBA counties as the front moves over the area. A
chc of rain will persist over the interior and north slopes during
the day Monday. Max temps will fall to normal across most of SLO
and SBA counties. Temps across VTA and LA counties will continue
to fall but will still be above normal.

Strong north to south gradients will develop once the trough axis
moves to the east of the region on Monday. The GFS and EC agree
that a strong north-northeast wind event is setting up for Monday
night and Tuesday. The GFS forecasts a 1040 mb surface high over
Idaho Tuesday morning, strengthening to a 1043 by Wednesday. The
GFS fcst LAX-DAG grad for Tuesday is -9 MB and 5.5 MB Wednesday
morning. There will be moderate north winds Monday night with the
strongest winds across the SBA south coast and the I-5 corridor.
The winds will turn to the NE Tuesday morning and a classic Santa
Ana will set up. It will be at least a moderate event and if the
upper level support lines up it could be a strong event. The Santa
Ana winds will continue into Wednesday but they will be weaker.

Monday will be the coolest day due to the clouds and lower hgts.
Max temps will rebound Tue and Wed but not as much as one might
think due to the large amount of cool air moving into the air from
the E. Min temps Tuesday and esp Wednesday will be below normal in
the non windy areas. Interior sections will likely see some frost
and perhaps even some freezing conds.

&&

.AVIATION...23/1140Z

At 0922Z at KLAX, there was a surface based inversion with the
top of the inversion around 1300 feet with a temperature of 29
degrees Celsius.

High confidence in CAVU TAF.

KLAX...High confidence in CAVU TAF. 30% chance for easterly winds
reaching 10 kt through 14z this morning.

KBUR...High confidence in CAVU TAF.

&&

.MARINE...23/230 AM...

For the Outer Waters, good confidence in current forecast. Winds
and seas are expected to remain below Small Craft Advisory (SCA)
levels through this morning. By this afternoon, northwest winds
are likely to increase to SCA levels across PZZ670/673, especially
the western portion through Friday afternoon, while PZZ676
remains just below SCA levels. There will be local gusts to 30 kt
on the very NW portion of PZZ676 this evening into Fri. Winds will
shift to the south late Friday night into Saturday with local
gusts to around 25 kt across the northern portion of the outer
waters. The best chance for widespread SCA level gusts will be by
Sunday afternoon when the winds shift back to the NW. 70%
confidence factor for SCA for the outer waters by late Sunday
afternoon into Monday.

For the Inner Waters, high confidence in current forecast. For
the waters north of Point Sal, winds and seas are expected to
remain below SCA levels through Sunday, although there is a 20%
chance of SCA level winds this afternoon/evening. For the waters
south of Point Conception, winds and seas are expected to remain
below SCA levels through Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      PM PST Friday for zones 670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
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.

&&

$$

PUBLIC...Rorke
AVIATION...Kaplan
MARINE...Kaplan
SYNOPSIS...Kaplan

weather.gov/losangeles



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