Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 100658
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1058 PM PST Mon Dec 9 2019

.SYNOPSIS...09/825 PM.

Skies will be partly cloudy through the week. Afternoon high
temperatures will be near normal through Wednesday and then above
normal on Thursday and Friday. By the weekend, clouds should
increase again and there is a slight chance of rain in the Ventura
County mountains.

&&

.SHORT TERM (MON-THU)...09/824 PM.

***UPDATE***

Latest GOES-W fog product imagery indicated mostly clear skies
across much of the forecast area, except low clouds were lingering
across interior SLO County including the Salinas River Valley.
There will be enough north and easterly flow to keep low clouds
banked up against the foothills in eastern SLO County and possibly
the Ventura County Mtns through tonight. Latest NAM- WRF Cross
Section model was hinting at patchy low clouds developing around
the Long Beach area, but based on current conditions with clear
skies, and some northerly winds across the region, will pull back
the low clouds for Long Beach and southern L.A. County coastal
areas for the overnight hours. There will be some local gusty
northerly winds across the I-5 Corridor and should filter down to
the Santa Clarita Valley overnight. There could be local gusty
Northerly winds across the western portion of the SBA South Coast,
mainly near Gaviota. Winds will not reach advisory levels
overnight.

High temperatures over the last 24-hours trended up anywhere from
3-12 degrees across a good part of the forecast area, except 3-5
degrees cooler across SLO interior locations where it stayed
cloudy all day. Best warming occurred across valleys and the
Central Coast thanks to some weak offshore flow off the San Lucia
Mtns. The warming was due to an elongated short wave ridge behind
the exiting trough into southern Arizona today that set up over
Southern Cal well into the west Coast of Canada. This ridge will
breakdown by Tuesday morning allowing for a more zonal flow over
Southern Cal. Skies will become mostly cloudy with high clouds
moving into the region late tonight and will persist into
Wednesday as a shortwave trough within the upper flow moves
through the area Tuesday afternoon into Wednesday morning. Not
expecting any rain with this quick moving disturbance. High temps
will be 2-6 degrees cooler in most areas tomorrow, except a few
degrees warmer across interior locations of SLO County. Overall,
highs will be around normal for this time of year.

***From Previous Discussion***

The main impact of the trough will be mostly cloudy skies and
cooler conditions for Wednesday along with some breezy to locally
windy conditions through the Interstate 5 Corridor and across
southern Santa Barbara County.

The trough should exit the region on Wednesday night and high
pressure aloft should build in through Thursday. Offshore flow
will develop and temperatures should warm to above normal on
Thursday. Advisory level northeast winds do not look likely for
Thursday, but breezy to locally windy conditions could develop
through and below passes and canyons.

.LONG TERM (FRI-MON)...09/155 PM.

Warmer than normal conditions should remain into Friday, then a
weak trough of low pressure will sag south for the weekend. PoPs
and rain chances were tweaked a bit, but the best chance for any
rainfall will be for the northern areas, including San Luis Obispo
County and the northern slopes of the mountains. Advisory level
winds should develop between Saturday and Sunday through the
Interstate 5 Corridor and across southern Santa Barbara County.

A moderate Santa Ana could be setting up for early next week in
the wake of the storm. ECMWF ensembles indicate several members
with strong winds across eastern Ventura and western Los Angeles
Counties. More confidence is placed more for the mountains and
the Santa Clarita Valley at this time, but the coastal and valley
area will have to be watched more closely. The latest GFS surface
pressure gradients suggest -5.1 mb pressure gradient between KLAX
and KDAG. Regardless, warmer conditions should expected for Monday
and Tuesday of next week.

&&

.AVIATION...10/0554Z.

At 2302Z at KLAX, there was no marine layer. There was a weak sfc
based inversion with a top near 700 ft and a temp of 17 C.

S of Point Conception...High confidence in TAFs except lower at
KLGB and KLAX where there is a 20 percent chc of LIFR cigs/vis 12z-
16z.

N of Point Conception...Moderate confidence with 00z TAFs. There
will be some LLWS +/- 10kt possible at KSBP KSMX with NE winds
aloft and NW-N winds at surface through 14Z. There is a 30 percent
of LIFR Conds 10Z-16Z. Low confidence on KPRB, with a 40% chance
for LIFR/IFR cigs lasting until 19Z.

KLAX...High confidence in TAF except lower confidence 10Z-16Z with
a 20 percent chc LIFR cig/vis. Good confidence that there will be
an east wind component less than 8 kt 10Z-18Z.

KBUR....High confidence in TAF.

&&

.MARINE...09/908 PM.

Moderate confidence Small Craft Advisory (SCA) conditions from
Point Conception to San Nicolas Island through tonight. Winds will
stay under SCA Tuesday through Wednesday morning, with SCA
conditions possible for the same area Wednesday afternoon into
Thursday. More widespread gusty NW to W winds possible Friday and
Saturday with building seas.

A large and long period W to NW swell will impact the coastal
waters later Thursday and continue through Saturday, resulting in
hazardous sea conditions and large breaking waves near shore.
Breaking waves at the Morro Bay and Ventura Harbor entrances are
possible.

There is a 30% chance for Patchy dense fog with low visibility
possible through at least Tuesday off the L.A. Coast.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PST Tuesday for
      zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

High surf is likely and minor coastal flooding is possible for
late this week at area beaches. Strong north winds possible
Sunday in southern Santa Barbara County, and parts of LA/Ventura
Counties.

&&

$$

PUBLIC...Kaplan/Hall
AVIATION...Rorke
MARINE...Kittell/CK
SYNOPSIS...Phillips

weather.gov/losangeles


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