Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/03/21

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 828 PM PDT Sat Oct 2 2021

.SYNOPSIS...02/827 PM.

Warm and dry conditions will continue across inland areas through
Sunday. A cooling trend is expected to begin Monday and continue
through the week. An upper level low pressure system will bring a
slight chance of showers and thunderstorms to portions of Los
Angeles and Ventura Counties Monday afternoon through Monday
night. A frontal system may bring rain to the entire area by
Thursday night or Friday.

&&

.SHORT TERM (SAT-TUE)...02/823 PM.

Another very warm day across inland areas with temperatures
soaring well into the 90s. A shallow marine layer influence kept
temperatures considerably cooler near the coast. Tonight`s
satellite imagery showing patchy low clouds and dense fog
returning to the Central Coast. South of Point Conception, skies
are clear at the moment, but still a descent chance of patchy
low clouds and dense fog developing overnight into early Sunday
morning across immediate coastal areas. 00Z Vandenberg sounding
and ACARS data near LAX showing a very shallow and strong marine
inversion, currently around 500 feet deep. Dense fog advisories
may be required for some of the coastal zones overnight.

Earlier this morning, the LAX-Daggett gradient peaked at -2.6 mb,
and a similar weak offshore pressure gradient is expected on
Sunday morning. So once again, light offshore breezes will
reinforce some very warm and dry conditions for inland areas on
Sunday, resulting in elevated to brief critical fire weather
conditions. Any offshore winds that develop overnight into Sunday
morning should mainly be focused in the mountains and foothills,
with gusts in the 20 to 25 mph range. With little change in the
offshore gradients and the boundary layer temperatures, looking
for another very warm day on Sunday across inland areas, with
temperatures climbing well into the 90s.

*** From previous discussion ***

An upper level low is forecast to develop several hundred miles
SW of the forecast area this afternoon and tonight then linger in
that area thru Sun. This will allow upper level ridging to persist
over SW CA during the period. Weak offshore flow should continue,
along with a strong near surface-based marine inversion. Low
clouds should move back into coastal areas tonight with at least
patchy dense fog likely. There is the possibility a Dense Fog
Advisory may eventually be needed for coastal areas tonight into
Sun morning. The low clouds should clear to or off the coast by
mid to late Sun morning. Otherwise, mostly clear skies will
prevail thru the second half of the weekend, with breezy offshore
flow in the morning turning onshore in the afternoon. Temps on Sun
are expected to tick up a couple more degrees, with highs about
6-12 deg above normal away from the immediate coast. Highs will be
generally in the upper 80s and 90s for the inland coastal areas,
vlys and lower mtns.

More low clouds and fog are expected for the coastal areas Sun
night into Mon morning, and patchy dense fog cannot be ruled out
thanks to a continued shallow marine inversion. In the meantime,
the upper level low off the coast is forecast to track slowly NE
toward the forecast area Sun night and Monday. The southerly flow
ahead of the upper low will pick up sub-tropical moisture and
spread northward into srn CA Mon afternoon, with plenty of mid-
level clouds expected to push into the area. There will also be
increasing instability and the upper height pattern will become
increasingly diffluent across the region. There is a slight chance
of showers for central and southern L.A/VTU Counties for Mon
afternoon and Mon night as moisture continues to stream northward
into the region. There should also be enough instability for a
slight chance of thunderstorms as well. This will be primarily an
elevated convective event. Any rainfall that does reach the ground
should be generally 0.10 inch or less. A few degrees of cooling
is expected for most areas on Mon but temps will still be several
degrees above normal overall.

The upper level low will move inland across srn CA on Tue with
weak upper level ridging moving into the forecast area by later
in the day. Low clouds and fog should affect the Central Coast
overnight into Tue morning, and into the L.A./VTU Coastal areas
by Tue morning. By late Tue morning into the afternoon skies
should be partly cloudy for the most part across the region altho
some low clouds may linger along the Central Coast beaches thru
the day. Temps will turn quite a bit cooler on Tue and should be a
few degrees below normal for the coast and most vlys, except near
normal for far interior vlys including the Antelope Vly.

.LONG TERM (WED-SAT)...02/206 PM.

A rather deep upper level trof is forecast to be over the E Pac
Wed thru Thu with a broad SW flow aloft over srn CA. An upper
level low is forecast to develop at the base of the upper level
trof well off the srn CA coast by late Thu. The deterministic GFS
ejects this upper level low quickly NE into central CA while
weakening Thu night and Fri, while the EC keeps the upper low well
off the coast during the period. The GFS pushes a large upper
level trof into CA Fri night and Sat, while the EC tracks a well-
defined upper level low into central CA by late Sat. The mean
ensembles wash out the more detailed features and just have a
broad upper level trof edging E and into CA Fri into Sat.

It looks like dry weather with persistent marine layer clouds for
the coast and vlys will prevail Wed thru Thu. There is a
possibility of some rain with a Pacific front moving into the area
late in the week, and due to model uncertainties went with the
NBM. A slight chance of rain is forecast for most areas from late
Thu night thru Fri altho there is a small chance (less than 15
percent) of rain even into Sat for some areas. Otherwise, dry
weather is expected thru Sat, with varying amounts of clouds
including marine layer clouds again by Fri night. Temps Wed thru
Sat are expected to be on a general cooling trend, and should be
several degrees below normal for most areas thru the period.

&&

.AVIATION...03/0034Z.

At 00Z, the marine layer was 500 feet deep at KLAX. The top of
the inversion was at 1300 feet with a temperature of 28C.

Moderate confidence in the 00Z TAFs for almost all coastal
airfields due to uncertainties with the timing and extent of low
clouds and VLIFR conditions tonight into Sun morning. For KSBP and
KSMO the low clouds and dense fog should move in between 04Z-05Z
this evening then linger until around 15Z Sun morning. For KSBA,
KOXR, KSMO and KLAX the low clouds and LIFR conditions are
expected between 07Z and 10Z later tonight and persist until
around 15Z- 17Z. There is only a 50% chance the low clouds may
move into the airfields S of Point Conception. The timing of the
onset and dissipation of VLIFR conditions may be off +/- an hour
or two. Otherwise, VFR conditions are expected.

For KLGB and the remainder of the inland airfields, there is high
confidence in the 00Z TAFs with VFR conditions expected through
the forecast period.

KLAX...Moderate confidence at best in the 00Z TAF. There is a 50%
chance of VLIFR conditions from 10Z-15Z Sun morning. Otherwise,
VFR conditions are expected thru the forecast period.

KBUR...High confidence in the 00Z TAF with VFR conditions expected
through the forecast period.

&&

.MARINE...02/1257 PM.

High confidence in the current forecast. Winds and seas are
expected to remain below Small Craft Advisory (SCA) levels for all
of the coastal waters through Wednesday. There is an increasing
chance of SCA level winds after Thursday with gales possible on
Friday.

Areas of dense fog is expected to affect most of the coastal
waters this morning. Dense fog will likely affect most of the
coastal waters overnight tonight into Sunday morning.

There is a 10 percent chance of thunderstorms on Monday afternoon
and night over the waters south of Pt. Conception.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (TUE-SAT).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/Sirard
AVIATION...Sirard
MARINE...Sweet
SYNOPSIS...Gomberg

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