351
FXUS66 KLOX 131525
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
825 AM PDT Thu Jun 13 2024

.SYNOPSIS...13/822 AM.

Low clouds in coastal and valley areas will clear slowly today.
There will be gusty north winds Friday through the weekend,
especially in portions of Santa Barbara County and the mountains.
Expect more sun and a big warm up Friday and Saturday, especially
inland. Temperatures return to more seasonal on Sunday.

&&

.SHORT TERM (TDY-SAT)...13/815 AM.

***UPDATE***

Temperatures are down 3-5 degrees this morning in much of the area
and even more in San Luis Obispo County with the extensive low
stratus. Aside from the marine layer bringing some local drizzle
this morning, the short term focus is on the upcoming wind and
warmer temperatures. It still looks like gusty NW to N winds will
reach Wind Advisory levels on Friday across the southwestern SBA
County coast, the western Santa Ynez Mountains, and the I-5
Corridor; and then even stronger winds on Saturday evening. No
impactful changes in the short term from the previous discussion.

***From Previous Discussion***

A deep marine layer continued across the forecast area this
morning, running around 2500 feet deep or so. Low clouds and fog
were widespread in all coastal and valley areas with the exception
of the far interior valleys of SLO County and the Cuyama Valley.
Even in the far interior valleys of SLO County, there will likely
be some low cloud infiltration this morning, and clouds will push
into the lower coastal slopes from SLO County thru L.A. County.
There will likely be local drizzle as well, as model cross
sections show some lift within the deep moist layer.

An upper low centered about 200 NM SSW of KLAX early this morning
will move eastward to near San Diego this afternoon. Strong
onshore gradients will continue across the region. Clearing will
be fairly slow today, with skies becoming mostly sunny by late
morning in the valleys, but not until the afternoon across much of
the coastal plain. In some immediate beach locations, skies will
probably remain cloudy for much of the day once again. Max temps
should be within a couple of degrees of those observed Wed in
most areas, except there will likely be cooling across far
interior sections of SLO/SBA Counties. There will be some gusty
west winds in the mtns and the Antelope Valley this afternoon and
evening but they should remain below advisory levels.

The upper low will continue to move eastward tonight and Fri, and
a weak broad upper ridge will build into the region. The marine
layer will likely begin to shrink in depth due to height rises, so
expect less inland penetration of the low clouds tonight/Fri
morning, with clouds likely below the coastal slopes, and possibly
not even pushing into the Santa Clarita Valley. With weakening
onshore flow, expect faster clearing in most areas Fri, with the
sun probably making an appearance at most beach locations. Rising
heights, weakening onshore gradients, and decent warming at 850
and 950 mb should lead to significant warming on Fri across
interior areas. Max temps in most valley, mtn and desert
locations will be 5 to 10 degrees warmer on Fri than they are
today, and some locations, such as in the Salinas Valley, max
temps may be 20 degrees or more higher than those today.

N-S gradients will increase sharply late Fri into Fri night, and
gusty NW to N winds will likely reach Wind Advisory levels across
the southwestern SBA County coast, the western Santa Ynez
Mountains, and thru the I-5 Corridor. Low clouds should be less
widespread, especially in the valleys and across SLO/SBA Counties
Fri night/Sat morning, and in fact, may be confined to southern
and eastern L.A. County. Gusty N winds will keep temps elevated
Fri night in the mtns/foothills, especially in SBA County.

An upper low will move into the Pac NW Fri night/Sat, with a broad
trough sagging southward down the West Coast. N-S gradients will
continue to increase across the region Sat. Expect any low clouds
to clear fairly quickly Sat. Falling heights may bring a bit of
cooling to interior areas Sat, but strong N-S gradients will
likely bring some warming to coastal and valley areas. This will
be especially true for the south coast of SBA County. Winds will
remain gusty from the NW-N across southwestern SBA County and the
I-5 Corridor, and will likely increase and become more widespread
Sat afternoon, affecting the Central Coast, the interior mtns of
SBA County and northern Ventura County, the Antelope Valley and
foothills, and some L.A. County valley locations.

N-S gradients will peak across the region Sat night, with models
showing an offshore gradient of over 5 mb between KSBA and KSMX,
and increasing offshore gradients between KSBA/KBFL and KLAX/KBFL.
There will also be increasing W-NW flow at 500 mb, strengthening
NW winds at 700 mb and N winds at 850 mb. At the same time, cold
air advection will spread into the region late Sat, and subsidence
will increase. This will bring the potential for NW-N winds to
increase to damaging levels across much of southern SBA County
including the foothills near the cities of Santa Barbara and
Montecito, the northern mtns of VTU County, the I-5 Corridor, and
the western Antelope Valley foothills. Have issued a High Wind
Watch from Sat evening thru Sun morning for the potential for wind
gusts of 60-70 mph in the more wind prone locations in these areas.

.LONG TERM (SUN-WED)...13/514 AM.

The powerful NW winds across SLO/SBA Counties and the coastal
waters will gin up a good eddy circulation across the inner waters
late Sat night/Sun. This will set up the age-old battle between
the NW flow and the eddy, making for a difficult cloud forecast
for Sat night/Sun morning. If the northerly flow wins out, some
gusty winds will affect the L.A. County valleys, and clouds will
be confined to southern L.A. County. There may also be clouds
across southern portions of the Central Coast due to northerly
upslope flow against the northern slopes of the Santa Ynez Range.
If the eddy wins, low clouds will push farther north and west,
possibly into the valleys of L.A./VTU Counties. Not only will
cloud cover be dependent on the outcome of the eddy/NW flow
battle, but so will max temps Sun. In general, expect a few
degrees of cooling Sun as heights fall, but cooling will be more
significant and widespread in areas south of Pt Conception if the
eddy becomes the dominant player.

N-S gradients will remain steep across SLO/SBA Counties Sun into
Mon morning, so advisory level NW winds are likely in southern
SBA County again late Sun afternoon into Sun night. Low clouds
should become more widespread south of Pt Conception late Sun
night/Mon morning. There should several degrees of cooling in most
areas Mon as heights continue to fall.

An upper low will move thru the Pac NW Mon and into the northern
Rocky Mountains Tue, with a sharpening trough across CA. The
trough axis will be located right across the region Tue, then it
will move to the east Wed. N-S gradients will remain decently
offshore across SLO/SBA Counties Mon night, then actually
increase Tue night. This should keep gusty N winds late each
afternoon/evening across southern SBA County Mon thru Wed. Expect
night thru morning low clouds to remain fairly minimal across SLo
and SBA Counties, with clouds in most coastal and valley areas of
L.A./VTU Counties. Expect minor changes in max temps Tue with some
warming possible Wed as heights begin to rise.

&&

.AVIATION...13/1523Z.

At 1500Z at KLAX, the marine layer was 1900 ft deep. The top of
the inversion was at 3500 ft with a temperature of 21 C.

High confidence in deserts TAFs, but low to moderate confidence
in coastal/valley TAFs. Timing of dissipation of CIG/VSBY
restrictions could be +/- 2 hours of current forecasts, with a
30% chance that coastal sites south of Point Conception may not
clear this afternoon. For tonight, high confidence in return of
CIG/VSBY restrictions to coastal/valley sites, but only moderate
confidence in timing and flight category.

KLAX...Moderate confidence in TAF. Timing of dissipation of
CIG/VSBY restrictions today could be +/- 2 hours of current 20Z
forecast (with a 30% chance that CIG restrictions will not
dissipate). For tonight, timing of return of CIG/VSBY restrictions
could be +/- 2 hours of current forecast with a 40% chance
conditions could drop to LIFR levels. No significant easterly wind
component is expected.

KBUR...Moderate confidence in TAF. Timing of dissipation of
CIG/VSBY restrictions today could be +/- 2 hours of current 18Z
forecast. Timing of return of LIFR conditions could be +/- 2 hours
of current 08Z forecast.

&&

.MARINE...13/824 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds will develop late
tonight and Friday morning, then will increase to Gale Force
levels from Friday afternoon through Monday. Seas will peak in the
12 to 15 foot range this weekend. GALE WATCHES are currently in
effect from Friday afternoon through Monday, but these will likely
be upgraded to warnings this afternoon. Additionally, there is a
30% percent chance of Storm Force gusts (48 knots or greater)
Friday night through Sunday night.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Today through Friday morning,
winds and seas will remain below SCA levels. From Friday afternoon
through Monday, a combination of at least SCA level winds and
seas can be expected. Additionally, there is a 40% chance of Gale
Force Winds Saturday afternoon through Sunday night.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For the Santa Barbara Channel,
high confidence in SCA level winds developing Friday afternoon and
continuing through Monday with a 40% chance of Gale Force Winds
across the western half of the Santa Barbara Channel Saturday
afternoon through Sunday night. For the rest of the southern
Inner Waters, there is a 30-40% chance of SCA level winds Saturday
and Sunday.

Across all the coastal waters, steep and dangerous seas can be
expected this weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch in effect from Saturday evening through
      Sunday morning for zones 349>353-377-378-381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 2 AM to 2 PM PDT Friday
      for zones 670-673-676. (See LAXMWWLOX).
     Gale Watch in effect from Friday afternoon through Monday
      afternoon for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB/jld
AVIATION...RAT/Cohen
MARINE...RAT/Cohen
SYNOPSIS...jld

weather.gov/losangeles

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