Weather Service Report


425 
FXUS66 KLOX 201534
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
834 AM PDT Sat Oct 20 2018

.SYNOPSIS...20/705 AM.

Offshore winds with warm and dry conditions continue today. 
Temperatures will be cooler Sunday through midweek then turn 
warmer late in the week. Patchy overnight coastal low clouds 
return Sunday morning. There is a slight chance of thunderstorms 
in the Ventura and Los Angeles County mountains Sunday evening.

&&

.SHORT TERM (TDY-MON)...20/832 AM.

***UPDATE***

Gradients are about 1 MB less offshore than they were ydy at this
time. Skies are clear across the forecast area and the forecast
was amended to remove the low clouds from the Central Coast. The
weaker offshore push and total lack of upper support has resulted
in much less offshore winds this morning. Temperatures will 
remain well above normal today but will not approach record 
levels. Max temps near the beaches will cool 3 to 5 degrees from 
yesterdays values due to less offshore flow and an earlier sea
breeze. Further inland along the coast there will be a few 
degrees of cooling but inland max temps will be similar to ydy's 
readings.

***From Previous Discussion***

A weak upper level low pressure system moves will move into the
region on Sunday. The prolonged offshore pressure gradients will
finally turn weakly onshore in the afternoon. This will result in
substantial cooling across coastal/valley areas on Sunday. Could 
also see a return of some low clouds and fog to the LA county 
coast by Sunday morning. If low clouds do develop, there is a good
chance fog will be dense along the coast. Another issue of Sunday
will be increasing pockets of mid level moisture and instability 
across the mountain areas on Sunday. The best moisture and 
instability (with Lifted Index values up to -6) are focused across
the Ventura county mountains and to a lesser extent across the 
eastern San Gabriel Mtns. There is currently a 20 percent chance 
of thunderstorms in the afternoon hours for both these areas. 
This looks reasonable especially across the Ventura County
Mountains considering the NAM, GFS, and National Blend all show 
some light precipitation over the Ventura county mountains on 
Sunday afternoon. Cannot totally rule out an isolated storm over 
other adjacent mountains areas. At the least, there will be some
cumulus buildups. 

For Sunday night into Monday, there will be a better chance of
more widespread low clouds and fog affecting coastal areas N of
Point Conception and at least portions of L.A. County Coast. High
temps will continue to trend down a few more degrees as a broad
upper trough persists over the region. High temps should range
from the 70s across coastal areas into the lower 80s for the
inland areas for the most part. There could be a few mid to upper
60s across the Central Coast.

.LONG TERM (TUE-FRI)...20/607 AM.

Both the GFS and ECMWF models are continuing to be in good
agreement with large scale features through the long period. A
persistent upper level trough will begin to swing out and fill in
as it moves into the Central Plains by Wednesday afternoon. A
relatively strong upper level ridge will begin to build in across
the Eastern Pacific off the California Coast Wednesday keeping 
much of the steering upper flow well to the north across the PAC 
NW. By Thursday, the upper ridge will expand eastward causing 
heights and boundary layer temps to rise. the GFS was advertising 
a -2 MB LAX-DAG gradient Friday morning. This lower resolution 
model usually is much weaker than the higher res models, therefore
there is a good chance that there will be increasing offshore 
winds to go along with the warmer conditions allowing for a 
significant warm up late next week, especially Friday and 
Saturday. Low clouds should not be an issue late next week with 
the return of offshore winds and warming.

&&

.AVIATION...20/1201Z.

At 12Z at KLAX, there was no inversion or marine layer at KLAX. 

Clear skies and VFR conds are expected across the area thru the pd.

Locally gusty N to NE winds will affect portions of L.A. and VTU 
Counties this morning, with local LLWS and mdt UDDF.
 
KLAX...High confidence in the 12Z TAF with VFR conds thru the pd.

KBUR...High confidence in the 12Z TAF with VFR conds thru the pd.

&&

.MARINE...20/832 AM.

For the outer waters, high confidence that winds will remain 
below Small Craft Advisory (SCA) level thru Mon morning. There is 
a 30% chance of SCA level NW winds Mon afternoon and Mon night, 
then a 40-50% chance of SCA level winds Tue thru Wed. However, SCA
level winds are likely across the northern outer waters zone Wed.

Across the inner waters n of Point Conception, winds should remain
below SCA levels thru Mon morning. There is a 30% chance of SCA 
level NW winds during the afternoon and evening hours Mon and 
Tue, then SCA winds are expected Wed.

For the waters S of Point Conception, winds should remain below 
SCA levels thru Wed, except there is a 20-30% chance of SCA level 
NW winds this morning from Pt. Mugu to Santa Monica. 

Patchy to areas of dense fog with visibilities one nautical mile 
or less will affect the northern inner waters (PZZ645) and the 
northern two outer waters zones (PZZ670 and PZZ673) through noon.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

A significant warming trend is possible late next week.

&&

$$

PUBLIC...Kaplan/Rorke
AVIATION...DB
MARINE...DB/Sirard
SYNOPSIS...Kj

weather.gov/losangeles

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