Acton Weather

000
FXUS66 KLOX 182347
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
347 PM PST Mon Nov 18 2019

.SYNOPSIS...18/328 PM.

A low pressure trough approaching the California Coast tonight will
bring significantly cooler conditions, and periods of rain as
well as mountain snow Wednesday and Thursday. Drier and warmer
conditions will return going into the weekend.

&&

.SHORT TERM (TDY-THU)...18/156 PM.

Synoptically, there is an upper-level ridge of higher pressure
extending from the eastern Pacific into mid-California, a cut-off
568 DM low about 600NM to our south, and some remnants of post-
tropical cyclone Raymond further southeast. The ridge will
retreat to the west allowing an upper-level trough to dig
southwards into the CWA by Tuesday evening and absorb the cut-off
system. The resultant low will be fairly deep at 547 DM and is now
forecast to track mainly over land. The area will still get its
first storm of the winter season with light amounts of rain, and
snow at higher elevations. The low will exit to our east by
Thursday afternoon.

The last day of this heat event has already broken several records
in Los Angeles County. Afternoon temperatures have already started
to fall along the coasts as the winds have begun to turn onshore
at most locations. The upper-level trough will begin moving in
from the northwest tonight. Lower heights, increasing cyclonic
flow and the onshore flow at the surface should combine to bring
a return of marine layer stratus to the Central Coast. Skies will
become partly cloudy elsewhere as high clouds move off of the
upper low to the south.

Heights will end up about 15 DM lower Tuesday than today under the
trough. Skies will turn mostly cloudy as mid- and high-level
clouds move in from the north along with the trough. The clouds
and onshore flow will drop most temperatures about 15 degrees,
bringing them back down to normal values.

A chance of showers will develop after midnight Tuesday with the
best chance occuring over LA county. The best chances of rain
will be Wednesday morning and afternoon with rain tapering off
overnight Wednesday and pretty ending by early Thursday afternoon.
It`s likely that Orange and San Diego county will recieve the
majority of the rain from this system. Have introduced a slight
chance of thunderstorms in the forecast for Ventura and Los
Angeles Counties and the adjacent coastal waters as there are some
negative LIs and CAPE in the area. There could be brief heavy
downpours in thunderstorms.

Snow levels remain around 6,000 feet over Ventura and Los Angeles
Counties. Expecting up to 6 inches in the Los Angeles County
mountains and about half that in the Ventura County mountains. The
eastern San Gabriel mountains could see higher amounts.  Still a
possibility for a Winter Storm Advisory.

Rainfall amount estimates call for less than a tenth of an inch
across SLO and most of SBA counties. in San Luis Obispo County, a
tenth to a quarter of an inch for SBA county, up to a quarter for
VTA county and generally a quarter to a half inch for LA county.
The eastern San Gabriels will see the most rain with nearly an
inch of rain possible.

Temperatures will remain below normal on Thursday under the trough
and clouds.

.LONG TERM (FRI-MON)...18/202 PM.

Temperatures are forecast to make a gradual climb back to normal
through the extended period. Skies should finally be sunny again
by Sunday and the lack of cloud cover will make for some cooler
nights and a possible return to frost in interior locations. There
is another upper-level low near the area, but it is forecast to
remain in the east Pacific, to our west, and should not affect our
conditions. Higher pressure starts to push back in by Monday
afternoon.

&&

.AVIATION...18/2346Z.

At 1748Z, there was a weak marine inversion at KLAX with marine
layer depth of 700 feet. No marine clouds were present. The top
of the inversion was 1200 feet with a temperature of 29 degrees
Celsius.

Overall, high confidence in 00Z TAF package. VFR conditions are
anticipated at all sites south of Point Conception, with
a 20 percent chance of IFR/LIFR conditions across coastal TAFs.
Coastal sites north of Point Conception will likely see IFR
conditions overnight into Tuesday morning, with a 20 percent
chance of LIFR/VLIFR conditions.

KLAX...Moderate to high confidence in 00Z TAF as VFR conditions
are anticipated, except a 20 percent chance of IFR/LIFR conditions
on Tuesday morning. Easterly wind component is expected to
remain below 10 knots.

KBUR...High confidence in 00Z TAF as VFR conditions are
anticipated.

&&

.MARINE...18/134 PM.

For the Outer Waters, high confidence in current forecast. High
confidence in winds and seas remaining below Small Craft Advisory
(SCA) levels through tonight. On Tuesday and Wednesday, high
confidence in winds and seas reaching SCA levels with a 30% chance
of Gale force gusts Tuesday and Tuesday night. An SCA has been
issued for the outer waters. On Thursday and Friday, high
confidence in winds and seas remaining below SCA levels.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Winds and seas will remain below SCA levels
through tonight. On Tuesday and Wednesday, high confidence in
winds and seas reaching SCA levels (with strongest winds Tuesday
afternoon and evening). For Thursday and Friday, winds and seas
will remain below SCA levels.

For the Inner Waters south of Point Conception, high confidence in
current forecast. Overall, winds and seas will remain below SCA
levels through Friday. However, there is a 30% chance of SCA level
winds across the western half of the Santa Barbara Channel Tuesday
afternoon and evening.

&&

.BEACHES...18/136 PM.

A cold storm system will move over the region between late
Tuesday and Thursday. There is a 50 percent chance that high surf
could develop as the storm system moves over the region during
this time. The best chance of high surf is for the beaches along
the Central Coast and Ventura County.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect from 4 AM Tuesday to 2 AM PST
      Thursday for zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect from 10 AM Tuesday to 2 AM PST
      Thursday for zone 676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

A cooler and showery weather pattern is expected Wednesday
through Friday. There is a slight chance of brief heavy downpours
in thunderstorms, especially Wednesday to Thursday morning. High
surf is possible at west-facing beaches late Wednesday through
early Thursday.

&&

$$

PUBLIC...jld
AVIATION...Gomberg
MARINE...Sweet
BEACHES...Sweet
SYNOPSIS...Delerme/SMITH

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