000
FXUS66 KLOX 160629
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1029 PM PST Tue Jan 15 2019

...Aviation discussion updated...

.SYNOPSIS...15/1022 PM.

Periods of heavy rain, high elevation mountain snow, and gusty
winds will continue as a wet weather pattern will remain in place
through Thursday. Relatively warm and dry conditions will prevail
this weekend.

&&

.SHORT TERM (TUE-FRI)...15/916 PM.

Rain is tapering off to showers as a broad trough of low pressure
remains along the California coast this evening. While the
majority of the area received rainfall and the timing was pretty
good as the models advertised, rainfall amounts and rates fell
short of what the forecast expected. Virtually all model solutions
showed the potential for heavy rainfall across the area today and
focused it along the slopes of the Santa Ynez Range and Santa
Monica Mountains. All the ingredients (southerly low-level flow,
a surface trough farther south, lifting increasing as the storm
came ashore, etc.) never came together to produce heavier amounts
for the burn areas. Rainfall rates topped out near 0.60 inch per
hour across the Thomas burn area. Even heavier rainfall fell in
other portions of the region which could have produced minor to
significant mud and debris flows on the recent burn areas. An
inch of rainfall was observed offshore on San Nicolas Island in
about 45 minutes by the weather observer out on the island late
this afternoon. This same area of showers later produced near
0.45 inch in 10 minutes near Point Vicente.

Fog product imagery continues to indicate moist low levels of the
atmosphere remaining in place, which should continue to produce
intermittent shower activity across the area tonight. The best
chances for rainfall will be for Los Angeles County and for the
San Luis Obispo County coastal foothills tonight.

Rainfall coverage should increase late Wednesday morning or
Wednesday afternoon as an atmospheric river takes aim at
California. While the most rain will fall in northern California,
southern California should also receive a fair amount of rainfall.
NAM-BUFR time heights sections are impressive in advertising
between one and three inches of rainfall over the region. Local
amounts up to 5 inches are possible. While today`s system was
somewhat of a surprise to see it strengthening yesterday and last
night (to not materialize), the storm for Wednesday night and
Thursday has been modeled consistently to be wet and this storm
should be taken seriously. Isolated thunderstorms cannot be ruled
out either with this system as NAM-WRF solutions pushes a
majority of negative lifted index values over the area. Flash
flood watches may be needed for this last of three storm systems
this week.

***From Previous Discussion***

Precip will start to diminish Thursday evening with dry and
sunnier weather most areas Friday with the exception of north
facing mountains near the Grapevine where some isolated upslope
showers are possible in the morning.

.LONG TERM (SAT-TUE)...15/128 PM.

Odds are favoring a long stretch of dry weather starting Friday
and lasting through next week with periods of gusty offshore winds
at times and warmer temps. Models have backed off even further
with a system for late Sunday into Monday and even if that does
manage to hold together it would just bring some light rain to
northern areas with generally clear skies to the south.

&&

.AVIATION...16/0627Z.

At 06z at KLAX... there was no inversion.

Overall... Low to moderate confidence in the current forecast.
IFR/MVFR conditions at primarily Los Angeles County locations will
improve to VFR by 09z then all locations will become IFR/MVFR by
13z as breaks form in the cloud cover overnight with VLIFR/LIFR
conditions possible near daybreak. Scattered precipitation will
continue through the night across the region then the rain will
become more steady and heavier through the day.

KLAX... Low to moderate confidence in the current forecast.
IFR/MVFR conditions will improve to VFR by 08z then will become
IFR/MVFR by 13z as breaks form in the cloud cover overnight. There
is a twenty percent chance of VLIFR/LIFR conditions near daybreak.
Precipitation will continue periodically through the night then
will become more steady and heavier through the day. Easterly
winds up to 12 knots are likely after 18z.

KBUR... Low to moderate confidence in the current forecast. VFR
conditions will become IFR/MVFR by 13z as breaks form in the cloud
cover overnight. There is a twenty percent chance of VLIFR/LIFR
conditions near daybreak. Precipitation will continue periodically
through the night then will become more steady and heavier
through the day.

&&

.MARINE...15/802 PM.

Low to moderate confidence in forecast. For the outer waters,
winds have subsided below SCA thresholds, but short period seas
should remain over 10 feet through late tonight. Winds are
expected to increase again on Wednesday as another front
approaches, with south gales likely again (70%) Wednesday night.
Strong SCA winds will continue on Thursday, before winds shift to
the SW and begin to subside Thursday afternoon.

The nearshore waters off the Central Coast are expected to see
short period seas near or above 10 feet through late tonight. As
winds increase on Wednesday, SCA conditions will be possible in
the afternoon, increasing further Wednesday night with a 50%
chance of gales. SCA south winds will continue Thursday morning,
decreasing in the afternoon.

For southern Inner waters and SBA Channel, SCA winds will continue
through later this evening, with short period hazardous seas
through late tonight. SCA conditions will be possible again (50%)
Wednesday night and Thursday.

Large hazardous seas will continue through late in the week, with
large northwest swells crossing with short period southerly seas
caused by the strong S-SE winds. The largest swell will arrive
Thursday into Friday.

&&

.BEACHES...15/811 PM.

A series of large westerly swells will affect the coastal waters
through the week, along with periods of large and steep southerly
wind waves. A High Surf Advisory is in effect through Friday
evening, with a good chance that the surf will persist through
Saturday morning. The next large swell will arrive on Thursday,
with the potential for Warning level surf on many beaches Thursday
afternoon into Friday: over 20 feet on the Central Coast and over
15 feet along west facing beaches of Ventura and Los Angeles
Counties. With unusually high tides during the morning hours
starting Thursday, there will be a chance of significant coastal
flooding and beach erosion, especially Friday morning when surf is
highest. The very high tides will continue through the weekend,
but surf will begin to subside Friday night.

High tides of 6 to 7 feet are expected between 5:30 and 6 AM on
Thursday and Friday, with the largest surf expected Thursday night
into Friday. In addition to coastal flooding and beach erosion
issues, there is a potential for breaking waves across the Morro
Bay and Ventura Harbor entrances late in the week. Hazards
associated with the high surf will include strong and dangerous
rip currents, breaking waves near shore, and waves washing over
rock jetties.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 8 PM PST Friday for zones
      34-35-39>41-87. (See LAXCFWLOX).
     Winter Storm Warning in effect until 4 AM PST Wednesday for
      zones 53-54. (See LAXWSWLOX).
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (FRI-TUE).

Large high tides and surf could bring coastal flooding Saturday.

Gusty offshore winds could develop over the weekend into early
next week.

&&
$$

PUBLIC...Hall/MW
AVIATION...Kj
MARINE...Smith
BEACHES...Smith
SYNOPSIS...Kj

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