195
FXUS66 KLOX 031620
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
920 AM PDT Fri May 3 2024

.SYNOPSIS...03/909 AM.

A cooling trend will begin today with a deepening marine layer
through the weekend. A storm system will brush the area to the
north this weekend with a chance for light precipitation later
Saturday into Sunday. Night and morning low clouds and fog will
struggle to clear at the coast today, then spread back inland
tonight. A warming and drying trend will develop next week.

&&

.SHORT TERM (TDY-SUN)...03/919 AM.

***UPDATE***

The marine layer has deepened to around 3500 feet across the LA
Basin, sloping down to around 1000 feet along the Central Coast.
The eddy is a little weaker than yesterday but onshore flow is
stronger and it will take longer to clear the stratus today and
through the weekend. Still looks like a high chance of rain along
the Central Coast Saturday afternoon (around a quarter inch) as a
late season storm moves into northern California, but mostly just
brushes by our area. Farther south, rain chances will be Saturday
night into early Sunday and lighter, mostly under a tenth of an
inch. And like this morning some areas will see morning drizzle
both Saturday and Sunday. With the storm exiting to the east
Sunday and the flow shifting to the west/northwest there should be
much better clearing in most areas.

***From Previous Discussion***

The storm system, over the Gulf of Alaska this morning, will dig
south into northern California through Saturday night, brushing
the area to the north. A cold frontal boundary will drop south
into the region on Saturday, bringing rain to much of the area.
PoPs have been nudged higher in the latest forecast, going higher
than NBM solutions. All of the ensemble members have light
precipitation developing for areas north of Point Conception,
along the northern slopes of the mountains, and across eastern Los
Angeles County. The forecast is little more questionable for
southern Santa Barbara County, Ventura County, and western Los
Angeles County. The forecast trends wetter as deterministic
solutions are starting to trend more southwest to west with the
low-level flow pattern. The forecast trends more toward the
deterministic solutions south of Point Conception, buying into the
model trends. Model tabular forecast output suggests a high- to-
likely chance of rain for areas north of Point Conception, and
moderate-to-high chance for areas southwest of Point Conception.
There is a moderate chance that southern Santa Barbara County,
Ventura County, and western Los Angeles County could end up being
in a rain shadow effect as downsloping occurs from the Transverse
Ranges. Rainfall amounts will likely range from a quarter inch or
less, except a quarter to half inch across northwestern San Luis
Obispo County. Amounts will be highest for the northern portion of
the area and along the northern slopes of the mountains. Rainfall
will only amount to a few hundredths at most for most coastal and
valley areas south of Point Conception.

Gusty west to northwest winds will develop across many coastal
areas, into the Santa Ynez Valley, across southern Santa Barbara,
up into the Interstate 5 Corridor, and down into the Antelope
Valley. EPS solutions indicate good agreement across the area for
the potential for wind advisory, but a handful of solutions
indicate a gust potential over 55 mph at KSDB. This will need to
be monitored as we get closer as wind gusts have been trending
generally higher with each run.

A colder air mass will spread into the area between Saturday and
Sunday night with the cold front. Temperatures during this
stretch trend colder than NBM values, and Sunday could be a cold
day for May, similar to a February or March with 60s being common
across the coastal and valley areas.

.LONG TERM (MON-THU)...03/415 AM.

A warming and drying trend will develop for the work week next
week as high pressure aloft reestablishes. The forecast ensembles
agree with a warming trend extending through at least
Thursday. EPS solutions tend to hold onto the warming trend
extending into next weekend. EPS cloud cover means point to the
marine layer depth being kept in check, but confidence is moderate
at best in this solution as we are in May. The latest forecast
keeps some marine layer induced low clouds and clouds returning
to coastal areas by mid week.

&&

.AVIATION...03/1313Z.

At 12Z at KLAX, the marine layer was 2800 ft deep with an
inversion top at 4500 ft and a temperature of 14 C.

Low clouds and fog were widespread in all coastal and valley
areas, with clouds moving into the lower coastal slopes. Cigs
were mostly high IFR to low MVFR, except LIFR to VLIFR north of Pt
Conception, and in the valleys and foothills.

Skies should clear by mid to late morning in the valleys and by
noon on the coastal plain, but may linger all day at some beaches.
Expect similar conditions tonight, with widespread low clouds in
coastal and most valley areas, and low MVFR to high IFR conds,
except LIFR to VLIFR conds in the foothills.

KLAX...Low to moderate confidence in the 12Z TAF. There is a 30-40%
chance that cigs will not scatter out at all today. There is a 20%
chance of an E wind component of 7-8 kt thru 17Z and from 09Z-15Z
Sat.

KBUR...Low to moderate confidence in the 12Z TAF. There is a 30%
chance of cigs lingering until 20-21Z. There is a 30% chance of
cigs will arrive as early as 03Z tonight.

&&

.MARINE...03/723 AM.

For the Outer Waters, Small Craft Advisory (SCA) level winds are
expected to increase to Gales (70% chance) this afternoon, with
the strongest winds off the coast. Gales will continue thru late
tonight, then drop to SCA levels. Winds may even drop below SCA
level for a while Sat morning, but seas will remain above SCA
levels. SCA level winds are expected (80% chance) Sat afternoon,
then continue much of the time thru Tue. There is a 50% chance of
Gale force winds Sun afternoon/evening, then a 30-40% chance
during the afternoon/eve hours Mon thru Tue.

For the Inner Waters north of Point Sal, SCA level winds will
develop today, then continue thru late tonight. There is a 40-50%
chance of SCA level winds/seas during the afternoon/eve hours Sat,
then SCA winds are likely (70% chance) during the afternoon/eve
hours Sun thru Tue. There is a 30% chance of gales Sun
afternoon/eve.

For the Santa Barbara Channel, there is a 40% chance of SCA level
winds in western portions of the channel this afternoon thru late
tonight, then Sat afternoon/eve. SCA level W-NW winds are
expected Sat night thru late Sun night (80% chance), and are
likely (60-70% chance) during the late afternoon thru late night
hours Mon thru Tue. There is a 30% chance of gales Sun
afternoon/eve.

For the Southern Inner Waters, there is a 30% chance of SCA level
winds from Anacapa Island to Malibu during the late afternoon/eve
hours Sat. SCA level winds are likely (70% chance) Sat night thru
late Sun night. There is a 40% chance of SCA level winds during
the late afternoon thru late evening hours Mon thru Tue.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 645. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Saturday for zones
      670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Hall
AVIATION...DB
MARINE...DB/RAT
SYNOPSIS...MW/Hall

weather.gov/losangeles

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