Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 210751

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1251 AM PDT Sat Apr 21 2018

.SYNOPSIS...20/508 PM.

A high pressure system will bring above normal temperatures
away from the coast through Monday. Closer to the coast, a
coastal eddy will usher in night through morning low clouds and
fog. A low pressure system should arrive Tuesday for increasing
onshore flow and a cooling trend through the remainder of the work


.SHORT TERM (SAT-TUE)...20/909 PM.

The latest satellite imagery shows an upper-level ridge of high
pressure building into Central California this evening and a
farther upstream trough about 400 miles west of Seattle. A weak
upper-level trough sits near 27N and 128W, or about 700 miles
southwest of Los Angeles.

Ridging aloft will remain in place through Saturday and onshore
flow will weaken through Saturday, possibly turning weakly
offshore later tonight. A warming trend will take place on
Saturday, especially away from the coast. Much of the warming near
the coast will depend how much marine intrusion takes place into
Saturday morning. There is a chance that temperatures near the
beaches could be a tad too warm Saturday. Fog product imagery
does not look particularly impressive, but some semblance of
marine layer stratus is present giving some confidence in the
overall stratus forecast through Saturday.

The trough of low pressure to the southwest of the area will move
northeast into the Southern California on Saturday afternoon,
while the trough to the northwest phases and fills in behind it.
A cooling trend should develop for Sunday and Monday. Below
normal temperatures and a persistent marine layer should remain
in place for early next week.


.LONG TERM (WED-SAT)...20/158 PM.

Models seem to have settled down on a solution for next week,
keeping the upper low well west of the coast through at least the
middle of the week, then lifting it northeast into the Pac NW
Friday night into Saturday. This will keep some ridging along the
coast going through mid week at least, however onshore flow
strengthens slightly each day. So it looks like the marine layer
should be a consistent feature for coast and coastal valleys next
week with temps near to slightly above normal. A strong onshore
push will likely cool temps to below normal by the end of the week
with some gusty winds in the Antelope Valley.



At 06Z, the marine layer depth was around 800 feet deep at KLAX.
The top of the inversion was near 2300 feet with a temperature
of 18 degrees Celsius.

Expect areas of stratus with low MVFR to high IFR conds across the
Central Coast and Santa Ynez Valley overnight. Skies are expected
to clear late tonight or very early Sat as flow turns offshore.

Areas of low clouds with low MVFR/high IFR conds are expected to
develop across the L.A. County coast overnight and linger thru mid
morning Sat. There is a chance that clouds will push into coastal
sections of VTU County.

KLAX...Moderate confidence in the 06Z TAF. There is a 20-30%
chance that conds will remain VFR through Sat evening.

KBUR...High confidence in VFR conditions through the period.
There is a 10-20% high IFR to low MVFR conditions between 13Z and


.MARINE...20/745 PM.

Low confidence in the fog forecast, but dense fog is possible now
through the weekend. High confidence in widespread short period
seas tonight, caused by gusty northwest winds over the outer
waters. The seas should

High confidence in Small Craft Advisory (SCA) winds from the
Central Coast to San Nicolas Island through tonight, with weaker
and more borderline SCA over the outer waters through the
weekend. Over the inner waters from the Santa Barbara Channel to
the San Pedro Channel, SE winds will form each morning, up to 15
kt through the passages and channels, with accompanying choppy
seas. Typical onshore winds expected in the afternoon, with near-
SCA west winds in the far western Santa Barbara Channel.


PZ...Small Craft Advisory in effect until 3 AM PDT early this
      morning for zones 645-676. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 670-673. (See LAXMWWLOX).



No significant hazards expected.



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