Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/05/20

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 821 PM PDT Sat Jul 4 2020

.SYNOPSIS...04/751 PM.

A warming trend will continue through the weekend as high pressure
builds aloft. Very warm temperatures are expected inland, with
highs 4-10 degrees above normal on Sunday, before gradual cooling
takes place through midweek. Marine layer clouds will be limited
to a few coastal areas through Monday, with more widespread low
clouds for the coast and some coastal valleys by mid week. Gusty
Sundowner winds are expected Sunday night and Monday night.

&&

.SHORT TERM (SAT-TUE)...04/820 PM.

Upper level ridge of high pressure combined with weakening
onshore flow to bring significant warming across inland portions
today, including triple digit readings across the SLO county
interior valleys. This has also resulted in a shrinkage of the
marine layer, with ACARS data showing the marine layer depth
around 900 feet across the LA Basin this evening. Current
satellite imagery showing mostly clear skies this evening, but
some low clouds and fog are expected to redevelop late tonight
across the LA county coast, possibly spreading northward to the
Ventura coast.

Even warmer temperatures are on tap for Sunday across inland
areas, with triple digit high temperatures expected in the
Antelope Valley, SLO interior valleys, and lower mountains.
Boundary layer temperatures remain elevated across the mountains
and foothills the next couple of nights, so bumped up minimum
temperatures accordingly for these areas. Gusty sundowner winds
are expected to develop across the western portions of the SBA
south coast and foothills during the late afternoon and evening
hours on Sunday and Monday. The strongest winds are expected to be
focused from Gaviota to San Marcos Pass where wind gusts of 35 to
45 mph can be expected. The forecasted Santa Barbara-Santa Maria
gradients on Sunday evening and Monday evening are expected to
peak around -4 mb. The sundowner winds conditions are also
expected to bring additional warming and drying to foothills
areas, with warmest foothill areas climbing to around 90
degrees.

The combination of hot and dry conditions along with locally gusty
winds and drying fuels will bring elevated fire weather conditions
Sunday into Monday for interior areas and the western portions of
the Santa Barbara south coast and foothills. Please see more
details in the fire discussion below.

*** From previous discussion ***

Upper level ridging over the region today will persist thru Sun
before weakening slightly Mon. H5 heights are expected to be
around 590-591 today through Sun, then lower to around 589 dm for
Mon. A broad upper level trof over the E Pac will move into CA
Mon night and Tue. This will result in H5 heights over the
forecast area lowering to 586-589 dm from N to S.

The upper level ridging will help to keep the marine inversion
quite shallow thru Mon thanks to heating in the lower levels down
to the boundary layer. The inversion depth should be surface-
based N of Point Conception and around 700 ft or less S of Point
Conception tonight through Sun, with little change expected into
Mon. A slight increase in the marine layer depth to about 800-1200
ft can be expected Mon night into Tue morning. Low clouds and
locally dense fog should affect just the L.A. County coast
tonight into Sun morning. Night and morning low clouds and fog
should expand slightly thru early next week, and affect the
SBA County Central Coast and the coast of VTU/L.A. Counties by
Monday night. Otherwise, mostly clear skies can be expected across
the region thru Tue.

Afternoon W-E onshore pressure gradients (LAX-DAG) will increase to
around +7.3 mb Sun and +7.7 mb Mon according to the NAM. This
will keep afternoon breezy to locally gusty SW-W winds over the
coast and in the foothills and mtns mainly over L.A. County, and
in the Antelope Vly. There should also continue to be offshore
gradient trends for LAX-BFL, SBA-BFL and SBA-SMX during the
evening to morning hours tonight thru Tue morning. Offshore flow
will persist night and morning hours over SLO/SBA Counties and in
northern VTU County during the period. Gusty N canyon winds near
Advisory levels can be expected Sun evening and Mon evening for
the SBA County S coast and mtns especially W of Goleta. Gusty NW
winds at times can also be expected in the mtns along the I-5
corridor tonight into Mon.

Temps are forecast to be about 4-10 deg degrees above seasonal norms
for many areas away from the coast Sun, and about 2-6 deg above
normal on Mon before cooling to a few degrees below normal on Tue.
Highs in the warmest vlys and lower mtns should be in the 90s to
around 102 Sun, mostly in the 90s on Mon, and in the mid 80s to
lower 90s Tue. The hottest temps Sun will continue to be in the
SLO/SBA County interior vlys and Antelope vly.

.LONG TERM (WED-SAT)...04/149 PM.

The EC and GFS are in generally good agreement for the extended
period. The upper trof will weaken on Wed, then upper level
ridging will build back into srn CA Thu thru Sat altho the EC
forecasts an even stronger ridge building in compared to the GFS.
A blend of the models will result in H5 heights over the forecast
area of around 587-589 dm Wed increasing to 592-596 dm by Sat.

The marine inversion should increase to probably 1500-2000 ft
deep Wed before lowering again to below 1000 ft deep by Fri.
More extensive low clouds and fog are expected Tue night into Wed
morning and should affect the coast and many of the vlys. The low
clouds and fog should affect most coastal areas Wed night into Thu
morning, then shrink in coverage to just the L.A. County coast by
Fri night. Otherwise, mostly clear skies will continue across the
forecast area Wed thru Sat.

Temps are expected to be several degrees below normal Wed and Thu,
then warm to near normal to slightly above normal Fri, and to
about 2-5 deg above normal for many areas away from the coast on
Sat. Highs in the warmest vlys and lower mtns should reach the
80s to lower 90s Wed and Thu, and in the 90s Fri and Sat except
mid 90s to 102 in the Antelope Vly.

&&

.AVIATION...04/2336Z.

At 2335Z, the marine inversion at KLAX was based at 900 feet. The
top of the inversion was 2000 feet with a temperature of 26
degrees Celsius.

Overall, moderate to high confidence in 00Z TAF package. High
confidence in valley/desert TAFs where CAVU conditions are
anticipated through TAF period. For coastal sites, moderate
confidence in TAFs as marine layer stratus/fog development tonight
will be rather low confidence. There is a 30% chance of
LIFR/VLIFR conditions 08Z-16Z across the Central Coast. South of
Point Conception, IFR/LIFR conditions likely at KLAX and KLGB
between 11Z-17Z, with a 30 percent chance for KSMO/KOXR/KCMA/KSBA.

KLAX...Overall, moderate confidence in 00Z TAF. High confidence
in CAVU conditions through this evening. For tonight, moderate
confidence in return of CIG/VSBY restrictions, but low confidence
in timing (could be +/- 3 hours of current 11Z forecast) and
flight category (equal chance of IFR or LIFR). No significant
easterly wind component is expected.

KBUR...High confidence in 00Z TAF as CAVU conditions are
anticipated through the period.

&&

.MARINE...04/759 PM.

For the Outer Waters, moderate confidence in current forecast.
For PZZ670/673, moderate confidence in Gale force winds tonight,
with higher confidence for Sunday through Monday. There is a 50%
chance of Gale force winds continuing through Tuesday night. For
Wednesday and Thursday, SCA level winds likely. For PZZ676, high
confidence in SCA level winds tonight through Thursday (with the
strongest winds northwest of San Nicolas Island), with a 50%
chance of Gale force winds on Tuesday for this zone.

For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. High confidence in SCA level winds
developing this afternoon and continuing through Thursday with the
strongest winds during the afternoon and evening hours. There is a
30% chance of Gale force winds on Tuesday.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. For a majority of the southern
Inner Waters, high confidence in winds and seas remaining below
SCA levels through Thursday. The exception will be the western
Santa Barbara Channel, with a 50% chance of SCA level winds
from late afternoon and overnight Sunday through Thursday.

Patchy dense fog, with visibility 1NM or less, will impact the
waters south of Point Conception, especially PZZ655 and PZZ676.

There will be dangerous seas across much of the waters thru
Tuesday. There will be a combination of a long period south swell
thru early next week creating large waves nearshore and hazards
to drifting boaters, and a steep large short period swell.

&&

.BEACHES...04/755 PM.

High surf and strong rip currents are expected through early
Monday on Southern California beaches. A long-period south swell
will peak tonight and Sunday at 3 to 4 feet at 16 seconds. High
surf of 5 to 8 feet is expected on exposed south and southwest
facing beaches of Los Angeles and Ventura Counties, and 8 to 11
feet to exposed Central Coast beaches. The Santa Barbara south
coast should have minimal affects from this swell due to blockage
from the Channel Islands, but local sets to 5 feet and hazardous
rip currents are expected near Rincon Point.

The evening high tides will be quite high today and Sun, between
6.5 and 7 feet. High tides will be between 815 and 9 PM this
evening and from 9 to 945 pm PDT Sun evening. Within a couple of
hours on either side of high tide, there could be minor coastal
flooding of beaches and harbor walkways.

Pay attention to beach closures this weekend. In addition to
large surf and dangerous rip currents, dangerous breaking waves
from long period waves, similar to this event, have a history of
ocean rescues and drownings. Stay off the rocks and jetties near
the water`s edge.

&&

.FIRE WEATHER...04/755 PM.

Hot and dry conditions are expected across interior areas on
Sunday and Monday, where humidities in the single digits and teens
will be common. The driest air will be focused across the
Antelope Valley, mountains, and interior valleys of SLO County
where humidities as low as 5 percent can be expected. In addition,
locally gusty southwest to northwest winds (gusting between 25
and 40 mph) can be expected across interior sections, strongest
in the Antelope Valley. Warm and dry conditions are also expected
to linger through the nighttime hours in the foothills and
mountains. The combination of hot temperatures, low humidities,
locally gusty winds, and drying fuels will bring elevated fire
weather conditions to interior areas Sunday into Monday.

Elevated  fire weather conditions are also expected Sunday into
Monday across the western portions of the Santa Barbara south
coast and adjacent foothills, mainly late afternoon and evening
hours. These areas can expect gusty sundowner winds, mainly from
Gaviota to San Marcos Pass where wind gusts of 35 to 45 mph will
be common. The sundowner wind conditions will also bring warm and
dry conditions, with humidities lowering into the teens and 20`s
across foothill areas, while temperatures climb to around 90
degrees.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until noon PDT Monday for zones
      34-35-40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 645-676. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Tuesday for zones
      670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

Gusty Sundowner winds are likely Monday night over the Santa
Barbara County south coast and mountain which may lead to
hazardous driving conditions.

&&

$$

PUBLIC...Gomberg/Sirard
AVIATION...GOMBERG
MARINE...Smith
BEACHES...Smith
FIRE...Gomberg
SYNOPSIS...Smith

weather.gov/losangeles