423
FXUS66 KLOX 141650
AFDLOX

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

.SYNOPSIS...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.

&&

.SHORT TERM (TDY-SUN)...14/949 AM.

***UPDATE***

Marine layer clouds are rapidly retreating from the coastal
plains and valleys, with most of LA county under sunny skies.
Onshore gradients have significantly trended downward compared to
yesterday, with a 24 hr decrease of 3.7 mb for the northerly LAX
to BFL gradient.

The forecast continue to be on track, however with this update
some adjustments will be made to the winds and the respective
hazards. The High Wind Warning will be moved up to start this
afternoon for Santa Barbara Southwest Coast and the western
portion of the Santa Ynez Mountains, as the latest model runs of
the UCSB WRF indicate very high winds (gusts 50 to 65 mph)
beginning this evening. Additionally, a Wind Advisory has been
added for the Santa Clarita Valley this afternoon into tomorrow
morning, with gusts of 30 to 40 mph possible. Winds will be
strongest overnight for the northern portions of this zone
including Castaic Lake.

***From Previous Discussion***

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.

&&

.AVIATION...14/1634Z.

At 1600Z at KLAX, the marine layer was 1900 ft deep. The top of
the inversion was at 4400 ft with a temperature of 23 C.

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 TAF. 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 TAF. For tonight, there is a 20%
chance of CIG/VSBY restrictions developing after 08Z.

&&

.MARINE...14/934 AM.

For the Outer Waters, moderate to high confidence in current
forecast. Ongoing Small Craft Advisory (SCA) level winds 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. High-end Gale Force Winds are expected especially
over PZZ670 and PZZ673, where there is also a 20-30% percent
chance of Storm Force gusts (48 knots or greater) Saturday through
Sunday. On Tuesday, winds and seas are expected to subside to SCA
levels.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. High confidence in SCA level
winds developing today and increasing to Gale Force Winds Saturday
through Sunday when a GALE WARNING is 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
increasing to Gale Force Winds Saturday through Sunday when a
GALE WARNING is in effect. For the rest of the southern Inner
Waters, winds are not expected to be as strong, though there is a
20-30% chance of SCA level winds Saturday through Sunday.

Across all of the coastal waters, steep and dangerous seas can be
expected this weekend into at least early next week.

&&

.BEACHES...14/946 AM.

Hazardous beach conditions are expected to develop later today
into tonight, and then continue through this weekend and early
next week. Significant wind-wave energy from relatively short-
period swell -- around 10-second wave periods generated by Gale
Force Winds winds over the nearby coastal waters -- will impact
all of the beaches starting later today. This will bring elevated
surf conditions and dangerous rip currents through early next
week. The latest data suggests that surf of 4-8 feet will likely
affect the Ventura County beaches, where a High Surf Advisory is
in effect. Elevated surf, with a 30-50% chance for High Surf
conditions, is expected for west-facing beaches along the Central
Coast and Los Angeles County. Locally elevated surf is expected
for the Santa Barbara County South Coast beaches, as well.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect from 3 PM PDT this
      afternoon through Monday afternoon for zones
      87-340-346-362-366. (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).
     High Surf Advisory in effect from 3 PM this afternoon to 5 PM
      PDT Monday for zone 354. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 11 AM PDT Saturday for
      zones 645-650. (See LAXMWWLOX).
     Gale Warning in effect from 11 AM Saturday to 2 AM PDT Monday
      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/Schoenfeld
AVIATION...RAT/Cohen
MARINE...Cohen/RAT
BEACHES...Cohen
SYNOPSIS...DB

weather.gov/losangeles

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