000
FXUS66 KLOX 301915
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1215 PM PDT Fri Sep 30 2022

.SYNOPSIS...30/855 AM.

Temperatures will cool through the weekend with increasing night
to morning low clouds and fog. A slow warming trend is expected
to begin Sunday and run through Thursday. Light to moderate winds
and mostly clear skies away from the coast will prevail.

&&

.SHORT TERM (TDY-MON)...30/908 AM.

***UPDATE***

Morning stratus lines the coast from Los Angeles to San Luis
Obispo this morning, with several eddy circulations visible in
GOES imagery. Expecting clearing to the coast by later this
morning. Temperatures are down across the area as expected,
ranging from a couple of degrees along the coast to 10 degrees in
the Antelope valley. This is the start of a general cooling trend
through tomorrow. No impactful changes from the previous short
term forecast.

***From Previous Discussion***

Overall, 00Z models in good synoptic agreement through the short
term period. At upper levels, main feature is low that drops into
northern Utah today/Saturday then moves into Montana on Sunday.
Near the surface, moderate onshore flow is forecast through the
period.

Forecast-wise, a very benign weather pattern can be expected
through the period. With slight lowering of H5 heights and
continued onshore flow, the marine inversion should deepen over
the weekend. Stratus/fog will gradually increase in areal coverage
each night, pushing into the coastal valleys. Stratus should
dissipate nicely each day, but not out of the question to have
some beach areas remain cloudy into the mid-afternoon hours. Other
than the stratus/fog, skies should remain mostly clear through
Sunday.

As for temperatures, lowering thicknesses and increased marine
influence will result in a cooling trend for all areas through
Saturday. On Sunday, the temperature trends will be mixed. The
Central Coast will likely remain persistent while some slight
warming is expected for most areas south of Point Conception.

.LONG TERM (TUE-FRI)...30/217 AM.

For the extended, deterministic models, and their respective
ensembles, are on the same page. Main feature will be upper level
ridge that builds over the West Coast on Monday/Tuesday then
generally remains in place into next weekend.

Forecast-wise, this pattern will continue to bring rather benign
weather to the area. Onshore gradients gradually weaken through
the period (and even turn weakly offshore according to the
deterministic ECMWF) which should result in less widespread
stratus/fog coverage as H5 heights increase. Otherwise, skies will
remain mostly clear through the week. As for temperatures, a
gradual warming trend is expected for all areas through Thursday.
If the ECMWF gradients are correct, it could be a bit warmer than
currently forecast west of the mountains, but will wait and see
how that possibility plays out. As for winds, weak onshore winds
should prevail through the period.

&&

.AVIATION...30/1903Z.

At 19Z at KLAX, the marine layer was around 2200 feet deep. The
top of the inversion was around 3400 feet at a temperature of 22
C.

High confidence in VFR TAFs at KWJF, KPMD.

Moderate confidence in coastal and valley TAFs. Return of MVFR/IFR
cigs will generally be within 2 hours of forecast and within one
flight category (30 percent chance of at least brief IFR cigs).
There is a 30 percent chance of IFR cigs/vsbys at KPRB between
11-15Z. Patchy drizzle possible between 06Z-15Z, mainly along
south facing foothills, with a 10-20 percent chance of occuring
at KBUR, KSBA, and KSMO.

KLAX...Moderate confidence in TAF. Return of MVFR/IFR cigs likely
return between 23Z-03Z. Any easterly wind component will be less
than 5 knots.

KBUR...Moderate confidence in TAF. Timing of return of low cigs
may be off by two hours with brief IFR cigs possible.

&&

.MARINE...30/949 AM.

Patchy dense fog with visibility less than 1 statute mile is
possible this morning across the waters north of Point Conception.
Elevated seas of 6 to 8 feet across the outer waters will subside
this afternoon through tonight. High confidence that winds and
seas will remain below SCA levels through the weekend. A return of
SCA level NW winds are likely for at least the outer waters by
Monday evening into the middle of next week.

&&

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

&&

$$

PUBLIC...Thompson/jld
AVIATION...Munroe
MARINE...Munroe/Stewart
SYNOPSIS...jld

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox