Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 181043
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
343 AM PDT Thu Oct 18 2018

.SYNOPSIS...18/257 AM.

An offshore flow regime will bring above normal temperatures and
continued dry conditions through the rest of the work week.
Stronger offshore winds are possible Friday and Saturday. A
cooling trend is possible early next week as low pressure system
moves over the region.

&&

.SHORT TERM (TDY-SAT)...18/324 AM.

The latest fog product imagery shows patches of stratus clouds
pushing into the Central Coast and up the Salinas River valley
this morning. Patchy dense fog is occurring across the Central
Coast this morning with several sites below a half-mile in fog. A
dense fog advisory may be added later for the Central Coast as a
shallow marine layer is in place across the area.

Offshore flow remains in place across the area this morning as the
region sits on the backside of a cutoff trough of low pressure
now located over Utah and a developing upper-level ridge of high
pressure near 38N and 133W. The trough will elongated and break
apart as the ridge builds into the northern Intermountain Region
through Friday. The trough will then recenter off the southern
California coast through Friday. An offshore flow pattern will
receive some reenforcement as the trough recenters. Marginal
upper-level wind and thermal support exists for advisory level
winds. A wind advisory could be issued by future shifts for late
tonight and into Friday morning, but it looks to be on low-end of
criteria.

While warm and breezy to windy conditions will develop on Friday,
it is still uncertain how much moisture will slip in from the
east between Friday and Sunday as the trough recenters offshore.
Model solutions shows a marginal amount of moisture slipping into
eastern Los Angeles County, but the timing and amounts vary.
Convective parameters tip toward adding at least chance PoPs with
near zero lifted index values and K-index values near 35, but
model soundings show a capping inversion. With differences in
timing, and amount of moisture and instability, PoPs have been
nudged up just below mentionable thresholds. There is certainly a
non-zero chance of showers and thunderstorms between Friday
afternoon and Sunday morning. Sky coverage has been increased as
well to mention partly cloudy skies for now.

.LONG TERM (SUN-WED)...18/338 AM.

The trough will linger into early next week over the area, while
slowly drifting east into Tuesday. Some cooling is possible as at
weak onshore flow should develop across the area, but most areas
will remain above seasonal normals for this time of year.

Ridging aloft developing over the eastern Pacific Ocean will
build in for middle-to-late week. A warming trend looks on tap
and was tweaked slightly to introduce a bit more warming for the
Central Coast. The air mass should not get too warm as the ridging
aloft is rather flat.

&&

.AVIATION...18/0531Z.

At 0509Z at KLAX, there was a surface-based inversion. The top of
the inversion was around 900 feet with a temperature near 22
degrees Celsius.

High confidence in the current forecast. LIFR conditions will
affect KSMX thru late tonight. There is also a 20%-30% chance of
these conditions at KSBP as well, otherwise VFR conditions are
expected at all airfields through Thu evening.

KLAX...VFR conditions are expected throughout the period. Any
easterly winds are expected to remain less than 7 knots.

KBUR...VFR conditions are expected through the period.

&&

.MARINE...18/222 AM.

Outer Waters...High confidence that winds will remain below Small
Craft Advisory (SCA) level winds through this weekend. There is a
30% chance that a SCA will be needed for PZ676 Friday morning for
offshore winds through early afternoon hours. Mainly the eastern
portion. There will be areas of fog with visibilities less than
one nautical mile at times across coastal waters adjacent to the
Central Coast through this morning. There is a good chance similar
visibility issues could occur again late this evening into Friday
morning as well.

Inner Waters...N of Point Conception from Point Sal to Point
Piedras Blancas, Winds should remain under SCA levels through this
weekend. For areas S of Point Conception...Overall winds should
remain below SCA levels through this weekend, except there will
be a 50% chance for a SCA Friday morning through early afternoon from
Pt. Mugu to Malibu and less likely across the San Pedro Channel.
There will be a 20% chance that a SCA will continue into the
afternoon and Friday evening between Pt. Mugu to Malibu.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Fire Weather Watch in effect from late tonight through
      Saturday afternoon for zones
      240-241-244>246-253-254-288-547-548. (See LAXRFWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

No significant hazards expected.

&&

$$

PUBLIC...Hall
AVIATION...Sirard
MARINE...Kaplan
SYNOPSIS...Hall

weather.gov/losangeles


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