064 
FXUS66 KLOX 091827
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
1127 AM PDT Mon Oct 9 2023

.SYNOPSIS...09/937 AM.

Low clouds and patchy dense fog expected for coastal areas this 
morning. A cold front will bring cooler temperatures and gusty
northerly winds at times into mid-week. Offshore flow is expected
Thursday and Friday, bringing warmer and drier conditions as well
as gusty Santa Ana winds in some areas.

&&

.SHORT TERM (TDY-WED)...09/955 AM.

***UPDATE***

Marine layer stratus has returned to most coastal areas this
morning as a weakening cold front moves into northern California.
Cooler temperatures are expected today with a moderate onshore
push that will create breezy winds over the coastal waters and 
southern Santa Barbara County, especially later this afternoon
into this evening. Otherwise, most of the weather focus is on the
post-frontal northerly winds developing Tuesday and Wednesday,
then the offshore winds for Thursday and Friday. Hi res models
still indicating a robust wind event for southern Santa Barbara
County, the I5 corridor, and the Antelope Valley with the
potential for wind gusts in excess of 50 mph in some of the more
favored areas like the hills above Montecito and the Tejon pass,
strongest Tuesday evening into Wednesday morning.

***From Previous Discussion***

Pressure gradients were onshore already this morning, and are
forecast to increase through the day. Low clouds should clear in
the valleys by mid morning, and by late morning or noon or so
across the coastal plain. However, clouds could linger at some
beaches today, especially on the Central Coast. Temps at 950 mb
are forecast to be 2 to 4 Celsius lower today then they were on
Sun, perhaps even a bit more than that on the Central Coast. 
Heights will also fall across the region today as an upper trough
moves into the West Coast. As a result, expect max temps today to
be several degrees lower than they were on Sun in most areas. The
most significant cooling is expected to be in the valleys, where 
max temps may be 5 to 10 degrees lower than they were on Sun. 

An upper low will move through the Eastern Pacific tonight thru 
Tue night, then move into the Pac NW Wed. A broad W-NW flow 
pattern aloft will set up across the forecast area. A couple of 
weak surface fronts will dissipate as they move into the West 
Coast to our north, one tonight and another one Tue afternoon
and evening. They will likely each just bring some mid or high 
clouds to areas north of Pt. Conception. Increasing N-S gradients 
and some subsidence across Santa Barbara County will probably 
bring low end advisory level NW-N winds to the southwestern coast 
of SBA County and the Western Santa Ynez Range this evening 
thru late tonight. Gusty W winds in the Antelope Valley and Highway
14 corridor this afternoon/evening will likely remain below 
advisory levels, as will gusty NW winds thru the I-5 Corridor.

The marine layer may deepen a bit tonight/Tue morning, with 
widespread low clouds in most coastal and valley areas, with the
exception of the interior valleys of SLO and SBA Counties and the
Santa Clarita Valley. Also, northerly winds across SBA County may
keep clouds at bay there, at least thru late tonight. Onshore 
pressure gradients will increase Tue, so clouds may be a bit 
slower to clear. Winds have a better chance of reaching advisory 
levels in the Antelope Valley and through the Highway 14 Corridor 
Tue afternoon and evening. Heights will not change much, but cooling
at 850 and 950 mb should bring a few more degrees of cooling to 
most areas on Tue. However, northerly flow late in the day may 
bring some warming to southern SBA County.

Behind the second dry front late Tue and Tue night, N-S gradients
will increase, and there will likely be solid advisory level 
winds across much of coastal southwestern SBA County and the Santa
Ynez Range. Advisory level winds will likely develop through the 
I-5 Corridor as well Tue night.

The stratus forecast for Tue night/Wed morning is rather tricky.
Northerly flow and cooling could weaken the inversion enough to
disrupt the stratus layer, especially north of Pt Conception, but
northerly flow should cause clouds to bank up on the north facing
slopes of the Santa Ynez Range and build back into the southern
Central Coast and Santa Ynez Valley. Also, some low clouds will
likely affect the northern slopes of the Ventura County mtns. 
South of Pt. Conception, expect areas of low clouds in coastal 
and valley areas of L.A. and VTU Counties. There could even be 
some drizzle late Tue night/Wed morning, mainly across L.A. County
and eastern Ventura Counties as flow become more cyclonic. Skies 
should clear well in most areas Wed. Onshore gradients will 
weaken a bit, so expect less wind in the Antelope Valley. Max 
temps Wed should be similar to those Tue, as slight cooling at 
950 mb will be offset by weaker onshore flow. In fact, increasing 
N-S gradients across L.A. County may lead to slight warming in 
some areas.

.LONG TERM (THU-SUN)...09/452 AM.

Another round of gusty northerly winds is likely across SBA 
County Wed evening, then the flow will turn northeasterly by Thu 
morning. Pressure gradients between KLAX and KDAG become offshore
and increase to 4 to 7 mb offshore, depending upon the model. 
Some EC ensembles show decent NE winds across northwestern L.A. 
County and Ventura County Thu morning, with advisory level NE 
winds possible. The WRF shows low level moisture hanging tough 
across southern L.A. County, so there may be some low clouds and 
fog there Wed night and Thu morning. A weak upper ridge will 
briefly build into the West Coast, but heights do not change too 
much. However, offshore flow and warming at 950 mb should bring 
some warming Thu, at least to areas west of the mountains.

A broad trough will move into the West Coast Fri and flow will
turn onshore. This will likely bring some cooling to most areas.
There should also be more in the way of night thru morning low
clouds and fog Thu night and Fri. 

Heights will rise again across the region over the weekend as 
another ridge develops. Expect slight warming on Sat, especially 
inland, with more widespread warming likely on Sun. By Sat night 
and Sun, night through morning low clouds and fog should be 
confined to the Central Coast and possibly coastal sections of 
L.A. County.

&&

.AVIATION...09/1826Z.

At 1715Z at KLAX, the marine layer was 1300 feet deep. The top of
the inversion was around 2700 feet with a temperature of 24 C.

Low to moderate confidence for coastal and valley TAFs. High 
confidence in desert TAFs. Timing of flight cat changes may be off
by +/- 2 hours. A steadily deepening marine layer, now 1700 feet
at Vandenberg AFB and 1300 feet at KLAX, should continue with a
deepening trend through tonight and Tue morning. The marine layer
depth should increase to around 2000 feet north and south Tue
morning. This will allow the marine clouds to spread into the
valleys.

KLAX...Low to moderate confidence in TAF. Expecting MVFR
conditions to return tonight into Tue morning. There is a 40% 
chance of east winds from 11Z-17Z, however any east wind component
should be less than 6 kt.

KBUR...Low to moderate confidence in TAF. Expecting mostly MVFR
conditions to return tonight into Tue morning.

&&

.MARINE...09/939 AM.

No changes to the marine forecast in the morning update. 

Areas of dense fog are expected across all of the coastal waters
through this morning.

For the Outer Waters, NW winds will hold at Small Craft Advisory 
(SCA) levels south of Point SAL, with the strongest winds today 
south of Point Conception. The SCA winds will expand to the outer 
waters north of Point Sal Tuesday morning, and will persist for 
all the outer waters through late Wednesday night. Tuesday 
afternoon through Wednesay night there is a 50% chance of GALE 
Force winds for the outer waters south of Point Sal, and a 50% 
chance for the outer waters north of Point Sal for Wednesday
afternoon/evening. A GALE WARNING will be issued and extended to 
Wednesday evening for zones 673 and 676 this afternoon. A Gale 
Watch will be issued for zone 670 this afternoon covering 
Wednesday afternoon and evening. There is a 20% chance that the 
SCA winds in the outer waters will hang on through Thursday. Seas 
will increase Tuesday afternoon to steep, short- period, hazardous
levels of 8-13 feet by Wednesday, with a 30% chance of lingering 
into Thursday morning.

For the inner waters north of Pt. Sal, there is a 60-70% chance of
SCA winds during the afternoon and evening hours Tuesday and 
Wednesday.

For the Santa Barbara Channel, NW-W winds will increase across 
the western portion to SCA levels this afternoon through late 
night with a 30% chance of reaching advisory levels by late Monday
morning. Winds will likely reach SCA levels each afternoon and 
evening hours Tuesday through Wednesday. There is a 40% chance of 
Gale Force winds Tuesday evening across the western portion. Seas 
will increase in height Tuesday night with heights 3-5 feet 
common, and a 30% chance of 7-8 feet (across the western portion),
peaking Wednesday. There is a 20% chance of the seas lingering 
into Thursday morning.

For the southern inner waters, there is a 30-40% chance of SCA 
level W winds during the late afternoon through late evening hours
Tuesday and Wednesday from Anacapa Island to near Malibu. There 
is a 30% chance of N-NE SCA level winds nearshore from Ventura 
south to Santa Monica Thursday morning.

Otherwise, conditions will likely drop below SCA levels across all
waters by Thursday afternoon through Friday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect from 6 PM this evening to 3 AM PDT
      Tuesday for zones 349-351. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 9 AM Tuesday to 9 AM PDT
      Wednesday for zones 645-670. (See LAXMWWLOX).
     Small Craft Advisory in effect from 3 PM this afternoon to 9
      AM PDT Wednesday for zone 650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Tuesday for
      zones 673-676. (See LAXMWWLOX).
     Gale Watch in effect from Tuesday afternoon through Wednesday
      morning for zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW/DB
AVIATION...Sweet/Schoenfeld
MARINE...Sweet/Schoenfeld
SYNOPSIS...MW

weather.gov/losangeles

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