457
FXUS66 KLOX 161220
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
520 AM PDT Thu May 16 2024

.SYNOPSIS...16/353 AM.

Strong onshore flow and a persistent marine layer will remain in
place through the middle of next week. Night through morning low
clouds and fog will be a staple of the forecast, clearing to the
beaches each afternoon. Breezy to gusty onshore winds will occur
each afternoon and evening across the interior valleys and
adjacent foothill areas.

&&

.SHORT TERM (TDY-SAT)...16/354 AM.

The latest satellite imagery shows a blocking ridge of high
pressure firmly in place over the eastern Pacific Ocean early this
morning. An upper-level trough pushing through the Four Corners
area continues to exit the region early this morning. Strong
onshore flow remains across the area with a marine layer depth
well entrenched along the central and southern California coast.
KLAX AMDAR soundings indicate the marine layer depth up to around
3500 feet deep this morning, slightly deeper than what local 3-km
WRF solutions suggest. Given the depth of the marine layer, it is
not surprising to see low clouds and fog pushing well into the
coastal slopes of the mountains this morning.

Strong onshore pressure gradients will keep a deep marine layer
depth in place over the next several days. Low clouds will
struggle to clear from the land mass each afternoon. With minimal
changes expected in the pressure gradients through the weekend, a
May Gray pattern is well underway. Night through morning low
clouds and fog will be a staple of the forecast for the near
future. Patchy night through morning drizzle will occur at times,
especially as an upper-level trough of low pressure near 30N and
135W drifts slowly to the east through the weekend and provide a
bit more dynamics aloft to squeeze some precipitation out of the
moisture associated with the marine layer.

Away from the coast into the interior portions of the area, breezy
to gusty onshore winds will create elevated fire weather
conditions during the afternoon and evening hours when warmer
daytime temperatures and drier humidities combine with breezy to
gusty winds. Over the next several days, winds will be marginal
for advisory levels, but as the upper-level trough of low pressure
draws closer to the area over the weekend, winds could approach
advisory levels. EPS solutions suggest wind gusts approaching
advisory levels on Saturday afternoon and evening, and again on
Sunday afternoon and evening at KPMD and KWJF.

Lingering instability from the trough could bring a few isolated
showers to the mountains, but it will likely just be some clouds
over the mountains this afternoon and evening. Moisture parameters
are down much from yesterday, but PoPs are non-zero over the
mountains this afternoon and evening. As the trough offshore move
closer to the region, a slight chance of showers and thunderstorms
over the Ventura and Santa Barbara County mountains could reenter
the forecast over the weekend during the afternoon and evening
hours. Stay tuned to the latest as this could be a wrinkle that
changes the forecast.

.LONG TERM (SUN-WED)...16/349 AM.

A deep marine layer depth and strong onshore flow is likely to
continue into early half of next week, keeping the forecast near
persistence into at least Tuesday. The forecast changes little as
a deep marine layer and expansive low clouds field could bring the
threat of night through morning drizzle along the South Coast of
California.

The forecast ensemble members are highlighting the potential for a
weak trough of low pressure dropping south down the coast between
Wednesday and Thursday. Gusty northerly winds appear in a majority
of the EPS ensemble members at KSDB and KSBA, but there is some
spread in the ensemble members into late next week. Pattern
recognition in the deterministic solutions would confirm the
possibility of a tightening northerly gradient for late next week.

&&

.AVIATION...16/1220Z.

At 10Z at KLAX, the marine layer was 3800 ft deep. The top of the
inversion was 6500 feet with a temperature of 18 C.

Widespread clouds across the entire area early this
morning with the exception of the Antelope Valley, most mountain
locations and the far interior valleys of SLO and SBA Counties.
Conds were mostly MVFR, except IFR north of Point Conception, and
LIFR to VLIFR in the foothills and mtn slopes. Expect slow
clearing today, with skies clearing by noon in the valleys and
early afternoon across interior sections of the coastal plain. It
will likely stay cloudy near the coast, but cigs may rise into the
VFR category. Expect similar conds tonight, with clouds in all
coasts, valley and mtn slope areas. Conds will be mostly MVFR,
except LIFR to VLIFR in the foothills and mtns.

KLAX...Moderate confidence in TAF. There is a 20-30% chance that
cigs will scatter out between 21Z and 02Z. No significant
easterly wind component is expected.

KBUR...Moderate confidence in TAF. There is a 20-30% chance that
cigs will persist thru the day.

&&

.MARINE...16/506 AM.

In the Outer Waters, moderate to high confidence in the forecast.
There is a 30% chance that winds will reach Small Craft Advisory
(SCA) levels in the southern two zones (PZZ673/676) this afternoon
and eve, and a 30% chance of SCA level winds/seas in the entire
outer waters Sun thru Mon. Otherwise SCA conds are not expected.

For the Inner Waters N of Pt. Sal, high forecast confidence.
Winds and seas are expected to remain below SCA levels thru Tue.

In the Inner Waters S of Pt. Conception, moderate to high forecast
confidence. There is a 20-30% chance of SCA level winds in the
western portion of the SBA Channel this afternoon/evening and
again Mon afternoon. Otherwise, SCA conds are not expected.

&&

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

&&

$$AVDAFDLOX

PUBLIC...Hall
AVIATION...DB
MARINE...DB
SYNOPSIS...Hall

weather.gov/losangeles

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