-- Discussion containing changed information from previous version are highlighted. --
910
FXUS66 KLOX 141131
AFDLOX

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

.SYNOPSIS...13/909 PM.

Low clouds and fog will continue across coast and valleys through
Friday morning. High pressure developing aloft along with
increasing northerly flow will decrease marine layer coverage and
bring warmer temperatures and areas of very gusty winds Friday
through the weekend. Strongest winds will be in southern Santa
Barbara County and the mountains.

&&

.SHORT TERM (TDY-SUN)...
-- Changed Discussion --
14/431 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. Those areas may well stay
mostly clear this morning. The pressure gradient between KLAX and
KDAG was similar to what it was at this time on Thu, but are
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, and
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 on Thu. High
today in the warmest portions of the Antelope Valley and the
valleys of SLO County should get close to 100 degrees today.

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, pushing into
the southeastern SBA County coast this evening. Strong
downsloping in the warm airmass will likely cause rise 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 across
southern SBA County, where temps may remain in the 70s in the
foothills.

An interesting pattern weather-wise appears to be setting up for
Sat through early Sun, but unfortunately, confidence in the exact
details is rather low due to micro-scale 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, and below
that 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. There
is a good potential for more significant warming across interior
portions of the Central Coast, and more likely across 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 on Sun, though still above normal.

.LONG TERM (MON-THU)...13/125 PM.

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 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 and Thu as heights begin
to rise.
-- End Changed Discussion --

&&

.AVIATION...
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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.
-- End Changed Discussion --

&&

.MARINE...
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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.
-- End Changed Discussion --

&&

.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...
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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).
-- End Changed Discussion --

&&

$$

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

weather.gov/losangeles

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