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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KLOX 111940
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1240 PM PDT Thu Apr 11 2024

.SYNOPSIS...11/859 AM.

Warm and sunny conditions will continue today, except for some
morning low clouds and fog near the coast. Much cooler weather is
expected Friday through the weekend as another late season storm
moves into the region. Rain will begin Friday night with showers
lasting until Sunday.

&&

.SHORT TERM (TDY-SUN)...
-- Changed Discussion --
11/912 AM.

***UPDATE***

At this time, low clouds and fog have mostly subsided, beginning
another day of clear skies and above normal temperatures.
Highs today will reach the low-to-mid 70s for coastal areas, with
some inland valleys reaching the upper 80s. Winds today will be
light following a typical diurnal pattern, with higher relative
humidites than yesterday. No impactful changes in the forecast.


***From Previous Discussion***

A return to light onshore flow has brought a rapid return of a
shallow marine layer to many coastal areas this morning with some
very dense fog. While most coastal areas had already begun their
cooling trend Wednesday, the shift to onshore flow and the arrival
of the marine layer will push the cooling slightly farther inland
and even into some coastal valleys. For all other areas, today
will look and feel a lot like Wednesday.

The cooling trend will spread throughout the interior by Friday as
onshore flow strengthens ahead of another late season cold upper
low dropping south along the West Coast. Low clouds and fog will
spread into the valleys Friday morning with highs dropping into
the 60s to lower 70s.

By Saturday morning the upper low is expected to be just offshore
of the Bay area with a cold front extending south through Pt
Conception. The vast majority of ensemble solutions have rain
beginning along the Central Coast Friday night and spreading into
Ventura and LA Counties either Saturday morning or afternoon.
Latest models show 500mb temperatures dropping to around -33c over
SLO County so thunderstorms are a good bet there and northern SB
County as well with periods of heavy rain. Hi res models showing
gusty south winds developing in SLO and northern SB Counties as
well later Friday night and may need some low end wind advisories
there.

Ensembles are holding pretty steady with rain amounts, ranging
from around an inch for SLO/SB Counties (except up to 2 inches in
the mountains) to around a half inch for LA/Ventura Counties (one
inch in the mtns). Around 10-20% of the solutions are twice that
amount. Thunderstorms will also boost totals in local areas,
mainly north of Pt Conception.

Snow levels will be around 6000 feet for the main portion of the
storm with several inches of snow possible. May need either a
winter weather advisory or possibly a winter storm watch for some
mountains. Snow levels drop rapidly Saturday night and with a
secondary upper low rotating into the area by Sunday morning
there`s a chance for additional showers and thunderstorms with
snow down to as low as 3500 feet.

.LONG TERM (MON-THU)...11/330 AM.

There is lower confidence with the second part of the storm
Saturday night into Sunday but given the -28c to -30c 500mb temps
and some surface heating showers and even some thunderstorms are
certainly possible everywhere. Amounts will be much more variable
but an additional quarter to half inch of rain is possible. Snow
levels will be lowering to 3500-4000 feet Sunday morning with some
light snow possible over the Grapevine on Interstate 5.

A drying and warming trend will begin Monday and last through next
week. 80`s may are possible as soon as next Wednesday in the
warmer valleys.
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
11/1928Z.

At 1828Z, the marine layer depth was 500 feet deep with the top
of the inversion at 2300 feet with a temperature of 23 C.

Moderate confidence in TAFs. Marine layer clouds should extend
further inland tonight, reaching coastal valleys sites. Cig
heights should be a little higher than last night (near IFR), with
less prevalent dense fog. Arrival of cigs may be off by +/- 2
hours this evening.

KLAX...Arrival of OVC004-OVC008 cigs may be off by +/- 2 hours
this evening, and periods of 1/4SM vsby are possible from 08Z-14Z
Fri. No significant east wind expected.

KBUR...Arrival of OVC008-OVC015 cigs may be off by +/- 2 hours
late tonight, and there is a slight chance of periods of 1/4SM
vsby from 10Z-15Z Fri.
-- End Changed Discussion --

&&

.MARINE...11/858 AM.

High confidence in the current forecast through late tonight,
then moderate confidence through the weekend. Slightly higher
confidence in winds relative to seas.

For the waters southwest through northwest of the Channel Islands
and the nearshore waters along the Central Coast, there is a 40-70
percent chance of Small Craft Advisory (SCA) level winds this
afternoon and tonight, highest for the waters beyond 30 NM
offshore west and northwest of Point Conception. There is a
30-40 percent chance that SCA level winds could spread farther
south and southeast Friday. There is a likely (60-80 percent)
chance of widespread SCA conditions developing Saturday through
Tuesday night. There is a low-to-moderate (20-30 percent) chance
of GALES Monday night through Tuesday night, highest beyond 30 NM
offshore.

Inside the southern California bight, winds and seas will likely
remain below SCA levels through Friday night, then there is a
high-to-likely (50-70 percent) chance of SCA level winds
developing Saturday. For early next week, SCA level winds
will likely affect the western portions of the inner waters with a
40-60 percent chance of SCA level conditions developing each
afternoon and evening through Tuesday.

Dense fog, with visibilities of one nautical mile or less, will
impact the coastal waters this morning, and possibly again tonight
through Friday morning.

&&

.BEACHES...11/308 AM.

There is a moderate-to-high chance of low level high surf with
strong rip current activity at the beaches this weekend. Surf
will peak on Sunday at 7 to 10 feet for the Central Coast,
highest on west and northwest facing shores. For beaches south of
Point Conception, surf will be around 4 to 7 feet, highest on
west facing shores.

Larger surf is possible for early next week as a large northwest
swell builds into the coastal waters. Early guidance suggest
breakers 9 to 12 feet along the Central Coast between Tuesday and
Wednesday. South of Point Conception, west-facing shores could
see surf of 4 to 7 feet.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zone
      670. (See LAXMWWLOX).
-- End Changed Discussion --

&&

$$

PUBLIC...MW
AVIATION...Schoenfeld
MARINE...Hall/Schoenfeld
BEACHES...Hall
SYNOPSIS...MW/RS

weather.gov/losangeles

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