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436
FXUS66 KLOX 141209
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
509 AM PDT Fri Jun 14 2024

.SYNOPSIS...
-- Changed Discussion --
14/445 AM.

High pressure aloft and increasing northerly flow will bring
significant warming today, with additional warming in coastal and
valley areas Saturday. There will be areas of gusty northwest
winds this afternoon through Saturday afternoon, with some
damaging wind gusts across southern Santa Barbara County, the
mountains, and the Interstate 5 Corridor Saturday night. After
this morning, expect limited night and morning clouds through
Sunday. Some cooling is likely Sunday, with more significant
cooling Monday as night through morning clouds become more
widespread. A warming trend is expected Tuesday through Thursday.
-- End Changed Discussion --

&&

.SHORT TERM (TDY-SUN)...
-- Changed Discussion --
14/506 AM.

The marine layer has shrunk in depth a bit, and was now running
between 1500 and 1800 feet. Low clouds have become quite
widespread in coastal and most valley areas, with the exception of
the Santa Clarita Valley, interior valleys of Ventura County, and
the far interior valleys of SLO County. Clouds may become more
widespread in Ventura County, but expect the Santa Clarita Valley
to remain mostly clear. The pressure gradient between KLAX and KDAG
was similar to what it was at this time Thu, but is forecast to be
weaker this afternoon than on Thu afternoon. N-S gradients have
become offshore between KSBA and KSMX, and there were some locally
gusty NW to N winds across southern SBA County. However, winds will
likely remain below advisory levels in most areas this morning.
The gradient trends support faster clearing of the low clouds
today, and skies should be sunny in most areas by afternoon.

The upper low that was located near San Diego last evening has
moved into western Arizona early this morning, and weak ridge was
building into the region. The combination of heights rises,
warming at 850 mb and 950 mb, and faster clearing should bring
several degrees of warming to most of the region today, with max
temps up 5 to 10 degrees. Across the interior valleys of SLO
County and in the foothills of SBA County, max temps today may be
as much as 20 to 25 degrees higher than they were Thu. Highs
today in the warmest portions of the Antelope Valley and the
valleys of SLO County should get close to 100 degrees.

Gradients between KSBA and KSMX are forecast to increase to
between 4 and 5 mb offshore this evening, and gradients between
both KSBA and KLAX and KBFL will become decently offshore as
well. During this afternoon, NW to N winds should increase to
advisory levels across most of the SBA County mountains (including
the Santa Ynez Range), the southwestern coast of SBA County, the
northern mountains of Ventura County, the Interstate 5 Corridor
and the western foothills of the Antelope Valley. Advisory level
winds should push into the southeastern SBA County coast this
evening. Strong downsloping in the warm airmass will likely cause
a jump in temps across southern SBA County very late this
afternoon or this evening, with max temps possibly rising into the
lower to mid 90s in the foothills of the SBA County south coast
this evening. Advisory level winds will continue in these areas
through Sat afternoon.

With the increasing northerly gradients, expect minimal stratus
tonight and Sat, most likely confined to coastal sections of L.A.
County and possibly the San Gabriel Valley. Where it remains
windy, it will remain quite warm tonight, especially in southern
SBA County, where temps may stay in the 70s in the foothills.

An interesting pattern weather-wise appears to be setting up for
Sat through early Sun. Unfortunately, confidence in the exact
details is rather low due to microscale factors, such as peak
wind placement, and the possible presence of a very shallow marine
inversion. At first glance, the upper pattern does not look very
remarkable, with a nearly zonal flow pattern aloft across the
region. However, westerly flow will increase at 500 mb on Sat.
At lower levels of the atmosphere, northwest to north flow will
strengthen, all the way down to near the surface as north to south
gradients peak late Sat into Sat night. There will be an increase
in subsidence across the forecast area on Sat, and coupled with
the sharpening gradients, expect NW to N winds to increase again
late Sat into Sat evening.

Damaging wind gusts to 60 to 65 mph are looking more likely across
the mtns of SBA County, portions of the south coast of SBA County
including Refugio and Gaviota by early evening, and probably the
Montecito Hills area before midnight. Wind gusts to 60 mph are
also likely (though a bit less certain) across the northern VTU
County mtns, the I-5 Corridor and the western foothills of the
Antelope Valley. Have upgraded the High Wind Watches to Warnings
for all of these areas. Wind advisories may be needed for the
Central Coast and the Antelope Valley Sat afternoon and evening,
and the Santa Clarita Valley late Sat into Sat night.

The airmass will be quite warm to start to day Sat, with 950 mb
temps remaining around 80 degrees across southern SBA County after
peaking at near 90 degrees this evening. This is where the
forecast gets rather tricky. There will likely be several degrees
of warming in most coastal and valley areas on Sat, while there
will be slight cooling in the Antelope Valley, the interior
valleys of SLO County and the higher mountains elevations.
However, there is a good potential for more significant warming
across interior portions of the Central Coast, and more likely
in southern SBA County, specifically the Santa Ynez Range and the
south coast of SBA County. Max temps should have no problem
rising well into the 90s to around 100 in the Santa Ynes Range,
but the real forecast challenge is for around the city of Santa
Barbara and adjacent areas. If the gusty northerly winds make it
to the beaches Sat, max temps could even get close to 100 degrees
in the foothills around Santa Barbara, with highs in the 90s
possibly down to the beaches. It will not take much of a lingering
marine inversion to keep these high temps from reaching the
coast, but the threat is high enough to place all of southern SBA
County under a Heat Advisory beginning Sat morning, and continuing
through Sun evening. While Sunday is not expected to be quite as
warm as Sat, gusty north winds will likely keep temps in the 70s
or possibly lower 80s in the foothills all of Sat night, which
will limit the ability for cooling relief that nighttime often
brings to that area.

The strong winds will likely dimish below warning levels by mid
to late morning Sun, but with N-S gradients remaining steep,
advisory level winds are possible in some areas through Sun
evening.

Otherwise, expect minimal stratus again Sat night/Sun, though a
developing eddy circulation help to increase stratus across the
L.A. County, with clouds possibly reaching southern Ventura
County. Confidence on that is low. Heights will lower on Sun, and
temps at 950 mb will not be as high, so expect max temps to be a
few degrees lower in most areas, though still above normal.

.LONG TERM (MON-THU)...14/508 AM.

An upper low will move into the Pac NW Sun night/Mon, with a
sharpening trough across CA. N-S gradients will decrease, and
onshore gradients will increase between KLAX and KDAG. Expect more
widespread night thru morning low clouds and fog Sun night/Mon,
with several degrees of cooling in all areas. The trough will
linger across the region Tue, but northerly gradients will return,
which may bring some gusty north winds, a bit of warming and a
reduction in low clouds.

Rising heights should allow for gradual warming Wed and Thu, with
typical night thru morning low clouds in most coastal and lower
valley areas.
-- End Changed Discussion --

&&

.AVIATION...14/1042Z.

At 0900Z at KLAX, the marine layer was 1300 ft deep. The top of
the inversion was at 3500 ft with a temperature of 22 C.

For the 12Z TAF package, high confidence in desert TAFs and
moderate confidence in coastal/valley TAFs. Timing of dissipation
of CIG/VSBY restrictions from coastal/valley sites could be +/- 2
hours of current forecasts. For tonight, there is a 20-30% of
CIG/VSBY restrictions developing at sites forecast to be clear
tonight and a 30-40% chance that clear conditions will persist at
KSMO/KLAX/KLGB.

KLAX...Moderate confidence in 12Z TAF. Timing of dissipation of
CIG/VSBY restrictions could be +/- 2 hours of current 18Z
forecast. For tonight, there is a 30-40% chance that CIG/VSBY
restrictions will not develop. No significant easterly wind
component is expected.

KBUR...Moderate confidence in 12Z TAF. Timing of dissipation of
CIG/VSBY restrictions could be as late as 18Z-19Z. For tonight,
there is a 20% chance of CIG/VSBY restrictions developing after
08Z.

&&

.MARINE...14/342 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Small Craft Advisory (SCA) level winds this morning
will increase to Gale Force levels this afternoon and remain at
Gale force through Monday. Seas will peak in the 12 to 15 foot
range this weekend. GALE WARNINGS are in effect from this
afternoon through Monday. Additionally, there is a 20-30% percent
chance of Storm Force gusts (48 knots or greater) Saturday and
Sunday. On Tuesday, winds and seas are expected to remain at SCA
levels.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Today through Tuesday, high
confidence in a combination of SCA level winds and seas, with the
strongest winds in the afternoon and evening hours. Additionally,
there is a 40-50% chance of Gale force winds Saturday and Sunday.
Therefore, a GALE WATCH remains in effect.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For the western Santa Barbara
Channel, high confidence in SCA level winds developing today and
continuing through Monday. Additionally for the western half of
the Santa Barbara Channel, there is a 50-60% chance of Gale force
winds Saturday through Sunday and a GALE WATCH remains in effect.
For the rest of the southern Inner Waters, there is a 20-30%
chance of SCA level winds Saturday through Sunday.

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

&&

.BEACHES...13/738 PM.

There is increasing concern for hazardous beach conditions from
Friday afternoon through this weekend and into early next week.
Wind-wave energy from relatively short-period swell, around
10-second wave periods and generated by strong winds over the
nearby coastal waters, will impact the beaches starting late
Friday. This will bring elevated surf conditions this weekend
into early next week.

There is a 30% chance for High Surf conditions for west-facing
beaches along the Central Coast, and Ventura and Los Angeles
Counties through the weekend, and a 40%-60% chance of High Surf
conditions early next week. Locally elevated surf is expected for
the Santa Barbara County South Coast beaches as well. Dangerous
rip currents will be of concern for all beaches Friday through at
least early next week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect from 3 PM PDT this
      afternoon through Sunday evening for zones
      87-340-346-354-362-366. (See LAXCFWLOX).
     Wind Advisory remains in effect from 3 PM this afternoon to 6
      PM PDT Saturday for zones 349>353-377-378-381. (See LAXNPWLOX).
     Heat Advisory in effect from 9 AM Saturday to 8 PM PDT Sunday
      for zones 349>352. (See LAXNPWLOX).
     High Wind Warning in effect from 6 PM Saturday to 11 AM PDT
      Sunday for zones 349>353-377-378-381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 11 AM this morning to 11
      AM PDT Saturday for zones 645-650. (See LAXMWWLOX).
     Gale Watch in effect from Saturday morning through late
      Sunday night for zones 645-650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 5 PM PDT this afternoon
      for zones 670-673-676. (See LAXMWWLOX).
     Gale Warning in effect from 5 PM this afternoon to 2 PM PDT
      Monday for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...DB
AVIATION...RAT
MARINE...RAT
BEACHES...Cohen/Sirard
SYNOPSIS...DB

weather.gov/losangeles

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