Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 210555
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
955 PM PST Sat Jan 20 2018

.SYNOPSIS...
Clear skies and generally light winds will lead to below normal
temperatures tonight with areas of frost for the coldest valleys.
A gradually warming trend is expected through early next week as
weak ridging builds aloft. A weakening cold front will likely push
through the region later in the week, bringing wind and cooler
conditions and possibly widespread rain and mountain show showers.

&&

.SHORT TERM...(SAT-TUE)

Water vapor imagery this evening shows ridging aloft building
into the Northern California and the Pacific Northwest. A
northerly surface pressure gradient remains across the area this
evening but is weakening at this time. A drier air mass continues
to spread over the area as the ridge builds. Colder air settling
in behind the trough of low pressure, now moving into Desert
Southwest region, will bring a cold night tonight. Many interior
valleys and wind-sheltered locations will see temperatures near or
below freezing tonight and into Sunday morning. A freeze warning
remains in effect for mainly the Ojai Valley in the Ventura County
Interior Valleys for tonight through Sunday morning. A frost
advisory will likely be added for the Central Coast and the
Ventura County Coastal Valleys. Westlake Village is already 39
degrees currently and with the northerly surface gradient
weakening, temperatures will likely drop as clear skies and
lighter winds will allow for better radiational cooling tonight.

Ridging aloft will build in through Sunday bringing warmer and
drier conditions for Sunday.

*** FROM PREVIOUS DISCUSSION ***

An upper level trough will move through Washington state on
Monday, with a weak front moving down the coast. There is a
chance that light rain associated with this front clips SLO
county on Monday before it dissipates. Otherwise, the passing
front will bring another round of gusty but likely sub-advisory
northerly winds Monday afternoon and night. By Tuesday locally
breezy northeast flow will set up under a weak ridge aloft.

.LONG TERM...(WED-SAT)

Dry conditions with little change will continue Tuesday into
Wednesday over Los Angeles and Ventura Counties. San Luis Obispo
and Santa Barbara Counties however will likely see ample high
clouds and a little cooling in advance of the next storm system.

A cold low pressure system will push into Washington state later
Wednesday, with a cold front that will push down the coast. Each
day the computer projections are wavering as to how well the
front holds together, but the latest projections are trending
toward a more persistent front. As such, increased the chances for
rain on Wednesday night and Thursday. Still expecting any amounts
to be on the lighter side with minimal-to-no threats to burn
areas, but a lot can happen between now and then. The evolution of
the system still looks similar to the one we just had, with rain
and gusty southwest winds, followed by gusty northerly winds and
low snow levels Thursday night into Friday. Tejon Pass/Grapevine
snow is in the cards once again. To no surprise, temperatures
should plummet on Thursday and stay well below normal Friday and
Saturday.

&&

.AVIATION...

21/0540Z

At 0545Z at KLAX, there is no marine layer nor was there a sfc
based inversion.

High confidence in CAVU TAFs.

KLAX...High Confidence in CAVU TAF. There is a 30 percent chance
of northerly cross winds greater than 20 knots through 12Z.

KBUR...High Confidence in CAVU TAF. Periods of moderate wind
shear and turbulence is possible through 10Z.

&&

.MARINE...

20/800 PM

Across the southern outer waters zones (PZZ673, PZZ676) high
confidence in gales through late tonight. SCA conds are then
likely early Sun morning through Sun night, and possibly much of
the time through Tue night due to a combination of winds and seas.

Across the northern outer waters zone (PZZ670) SCA conds for
winds and seas will continue through tonight, then due to seas Sun
morning. SCA conds are then likely again Sun night due to winds
and seas, and Mon thru Mon night due to seas.

For the inner waters north of Point Sal, SCA conds are expected
due to winds and seas thru tonight. SCA conds are possible again
Mon and Mon night due to high seas.

Across the SBA Channel and the southern inner Waters, moderate
confidence that gale force gusts will end by 9 PM, with SCA level
winds and seas late this evening through late tonight. Then, SCA
conds are not expected again until Thu.

Very large NW swell will slowly subside overnight into Sunday.
Another long period NW swell will arrive in the water late Sunday
night, rising to 10 to 13 feet by Monday.

&&

.BEACHES...

20/130 PM

The large surf is expected to continue along west to northwest
facing beaches through this evening then diminish overnight
through Sunday.

For west and northwest facing beaches along the Central Coast,
surf will average 14 to 16 feet with local sets to 18 feet through
early this evening, then surf will slowly subside tonight through
Sunday. A HIGH SURF WARNING remains in effect from this through
900 PM PST this evening. The high surf may cause beach erosion
and will produce life-threatening rip currents. Minor coastal
flooding is possible in low lying areas such as parking lots,
especially near the times of high tide.

For west and northwest facing beaches south of Point Conception,
surf will average 4 to 8 feet into this evening. Local sets to 10
feet are possible on exposed west facing locations such as Ventura
Harbor. High surf will slowly subside tonight through Sunday. A
HIGH SURF ADVISORY remains in effect through 900 PM PST this
evening for these areas.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 4 AM PST Sunday for zones
      34-35. (See LAXCFWLOX).
     Frost Advisory in effect until 8 AM PST Sunday for zones
      34-35-45. (See LAXNPWLOX).
     Wind Advisory in effect until 10 PM PST this evening for
      zones 39>41-59-88-547. (See LAXNPWLOX).
     Freeze Warning in effect until 8 AM PST Sunday for zone 44. (See LAXNPWLOX).
     Wind Advisory in effect until 3 AM PST Sunday for zones
      52>54. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Sunday for
      zones 645-650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 AM PST Sunday for zone
      670. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PST Sunday for zones
      673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
Strong and impactful winds are possible Thursday and Friday over
the mountains and southern Santa Barbara County. Snow and travel
delays are possible over the Tejon Pass/Grapevine area Thursday
night into Friday.

&&

$$

PUBLIC...Hall/Kittell
AVIATION...Rorke
MARINE...Smith
BEACHES...Sirard
SYNOPSIS...Munroe

weather.gov/losangeles


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