Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 232331
AFDLOX

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

New Aviation Discussion

.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
is expected to return early next week with some gusty offshore
winds.

&&

.SHORT TERM...(TDY-SUN)

Another day of widespread and unseasonably record heat is
occurring across the region today. Many high temperatures have
tied or eclipsed record levels for today, including the hottest
temperature recorded on Thanksgiving Day at Downtown Los Angeles
since records began in 1877. With a high temperature of 91
degrees, so far, Downtown Los Angeles has broken the old mark for
Thanksgiving Day set on November 26, 1903. Remember, this
temperature is not the same as a daily record, since Thanksgiving
Day falls on the fourth Thursday in November. The only areas that
fell short of records for today were the Santa Barbara South
Coast and the Central Coast.

Strong high pressure, responsible for the hot and dry air mass in
place, will weaken and flatten through the weekend as a broad
trough over the Eastern Pacific Ocean slowly displaces the ridge.
Cooling, albeit slightly, will become more widespread on Friday
and Saturday, with better cooling spreading over the area on
Sunday and Monday.

The trough will approach the West Coast over the weekend with a
stronger cold front scheduled to push south into the area between
Sunday and Monday morning. Model solutions are offering up timing
differences with the arrival of the cold frontal boundary, but
good agreement exists for the possibility of precipitation, mainly
north of Point Conception. Shower activity cannot be ruled out
south of Point Conception at this point as model solutions do
bring some moisture and instability south, but the question that
lingers is "How much?"

PoPs have been increased substantially for areas north of Point
Conception as both ECMWF and GFS solutions increase 850 mb mixing
ratios in excess of 8 g/kg.

A northerly surface pressure gradient will develop and tighten on
Sunday night and Monday behind the frontal boundary. Gusty winds,
possibly reaching advisory levels, could develop through the
Interstate 5 Corridor and across Southern Santa Barbara County on
Sunday night and into Monday morning.

.LONG TERM...(MON-THU)

Model solutions continue to suggest a strong offshore flow pattern
developing Monday through Tuesday, then lingering into midweek.
At least, advisory level Santa Ana Winds look to develop along
with a warming and drying trend for Tuesday and Wednesday. The
offshore flow regime could linger into Thursday. GFS solutions
tighten KLAX-KDAG to -7.5 mb on Tuesday morning.

In wind-sheltered locations, clear skies and less winds will allow
for radiative cooling processes to be more efficient during the
overnight hours. As a result, the interior valleys such as the
Antelope, Cuyama, and San Luis Obispo County Valleys could have
some frost, and maybe freeze conditions for Tuesday and
Wednesday.

Model solutions are struggling with developing a trough over the
Eastern Pacific Ocean for late next week. Timing and run-to-run
consistency issues are plaguing the models at this time, but a
degree confidence exists to bring cooler temperatures and partly
cloudy skies for late next week.

&&

.AVIATION...23/2330Z...

Good confidence with 00Z TAFs. Weak to occasionally moderate LLWS
is possible for KBUR and KSBA from 02Z to 18Z. There is a 20
percent chance of MVFR haze at Coastal TAF sites between 08Z and
20Z.

KLAX...Good confidence in 00Z TAF. There is a 20 percent chance
of MVFR haze between 08Z and 20Z

KBUR...Good confidence in 00Z TAF.

&&

.MARINE...23/100 PM...

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds are expected
through Friday evening across PZZ670/673. For PZZ676, SCA level
wind gusts will be more localized. Winds will diminish all areas
on Saturday. However for Sunday through Tuesday, northwest winds
will increase to SCA levels with even a 30% chance of Gale force
gusts on Monday.

For the Inner Waters, moderate to 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 Friday afternoon/evening. On
Monday and Tuesday, northwest winds will increase with SCA level
winds likely. For the waters south of Point Conception, winds and
seas will remain below SCA levels through Sunday afternoon. For
Sunday night and Monday, there is a 50% chance of SCA level
northerly winds across western sections. On Tuesday, the winds
will shift to the northeast with a chance of SCA level winds from
Ventura south to Santa Monica.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 PM PST Friday 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.

&&

$$

PUBLIC...Hall
AVIATION...Munroe
MARINE...RAT
SYNOPSIS...Kaplan/B

weather.gov/losangeles



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