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000
FXUS66 KLOX 171752
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1052 AM PDT Wed Apr 17 2024

.SYNOPSIS...17/858 AM.

Dry but cooler weather is expected through Friday as a weak low
pressure system moves into the area. A warming trend is expected
for the weekend before cooler temperatures return next week.

&&

.SHORT TERM (TDY-FRI)...17/909 AM.

***UPDATE***

A weak low pressure system approaching from the west is turning
gradients onshore today. The marine layer has responded with
increasing low clouds and fog along the coast from LA to Oxnard
and soon southern SB County. By Thursday morning stratus should be
well entrenched along the entire coast up through at least SLO
County and likely into the coastal valleys as well. Temperatures
will be cooling off as well, initially just at the coast but by
tomorrow through all the valleys and interior areas.

***From Previous Discussion***

A weak trof will slide over the area on Friday and hgts will dip
to 574 dam. Onshore flow will be 2 to 3 mb onshore from both the W
and S. This will bring another round of slowly developing low
clouds across the coasts and most of the vlys. Ensemble gradient
fcsts now show even stronger afternoon onshore flow than on
Friday. This runs contradictory to the hi rez ensemble cloud
forecast which shows good clearing by afternoon. Will keep the
afternoon fcst sunny, but there is now a higher chc of some low
clouds lingering at the beaches in the afternoon. The other change
for the Friday forecast is with the max temps which have switched
from little change to a solid 3 to 6 degrees of cooling mostly
due to the lower hgts and increased onshore flow. Max temps across
the csts and vlys will in the mid 60s to mid 70s or 3 to 6
degrees blo normal. Despite the cooling the mtns and far inland
areas will end up about 6 degrees above normal.

.LONG TERM (SAT-TUE)...17/300 AM.

Model solutions both deterministic and ensemble based are in good
agreement in the long term.

Over the weekend a ridge will slowly build over the state and
hgts will reach 580 dam on Sunday. At the same time the onshore
flow will weaken. The marine layer cloud coverage will diminish on
Saturday and will likely be confined to the Long Beach area on
Sunday. Look for 3 to 6 degree of warming each day except that the
Central Coast will not see much change on Sunday. Sunday`s max
temps will end up 2 to 4 degrees above normal across the cst/vlys
while the mtns and far interior will be 5 to 10 degree warmer than
normal. Almost all of the vlys will see temps in the 80s.

A trof moves in on Monday and this along with a substantial
increase in onshore flow will bring a return of the low level
clouds in the morning. Max temps will fall 3 to 6 degrees.

The mdls begin to diverge on Tuesday but the most likely outcome
will be a deeper trof, more marine layer clouds and cooler temps.

Beyond Tuesday there is some signal that an upper low will move
close enough to bring light rain to the area (best chc SLO county)
but the ensembles are all over the place with the exact timing and
details.

&&

.AVIATION...17/1751Z.

At 18Z, the marine layer at KLAX was about 500 ft deep. The top
of the inversion was at 1800 ft with a temp of 20 deg C.

VFR conds are expected in all areas thru this evening, with just
some high clouds. Widespread low clouds are expected in all
coastal areas tonight, with IFR to LIFR conds, and local VLIFR
conds on the Central Coast. There is a 20% chance that LIFR conds
will spread into the valleys late tonight.

KLAX...Moderate confidence in the 18Z TAF. There is a 20% chance
that cigs tonight will be in the MVFR category and a 20% chance
that cigs will not arrive until as late as 12Z. Any east wind
component should remain less than 6 knots.

KBUR...High confidence in the 12Z TAF with VFR conds thru the pd.
There is a 20% chance of LIFR cigs after 11Z Thu.

&&

.MARINE...17/900 AM.

A very shallow marine layer will continue to bring dense fog to
most waters south of Point Conception this morning, and could
linger through the afternoon or evening. Improved but still
reduced visibility is expected by Thursday.

There is a 60 percent chance of Small Craft Advisory conditions
for the offshore waters off the Central Coast this afternoon and
evening. Otherwise, high confidence in generally light winds
through Friday. Southeast winds around 10 knots are expected each
morning from the Santa Barbara Channel to Orange County, with some
local enhancements through the Anacapa Passage and San Pedro
Channel.

Northwest winds will be increasing over the weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3
      AM PDT Thursday for zone 670. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/Rorke
AVIATION...MW
MARINE...Kittell
SYNOPSIS...MW

weather.gov/losangeles

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