Small Craft Advisory 4, NWS Los Angeles, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
209 PM PST Fri Jan 6 2017

.SYNOPSIS...
Active and wet weather pattern may continue for the next week across
Southwest california. The first storm will bring a one-two punch
of rainfall, first with heaviest rains focused across the Central
Coast Saturday and then more widespread rain late Sunday into Monday
morning. Additional storms will bring more opportunities for rain
to the area during the middle to end of next week.

&&

.SHORT TERM...(TDY-MON)

An upper low about 1000 miles west of the SFO is drawing up
subtropical moisture that is expected to arrive in our area
later tonight and Saturday. SB and SLO counties will continue to
be the focus of this moisture but it's likely that at least some
of it will bring rain to LA and Ventura counties as well.
Beneficial orographic effects will enhance the rainfall in nw SLO
county and the models were in decent agreement on roughly 1-3" of
rain there, but low lvl easterly flow across LA/Ventura counties
may limit what we see down this far south. Looking at cross
sections through the entire air mass though it appears the
easterly flow is confined to a very shallow zone near the surface
while the winds rapidly back to the south and southwest well below
850 mb which is significant for orographic assistance. So for now
am following the slightly higher precip amounts in the GFS/EC
solution over the lighter NAM for Saturday in the south. Still
considerably less than what the Central Coast will receive but
more than just a trace or few hundredths.

Moisture plume pushes north Saturday night and Sunday as high
pressure builds from the south. Rain still expected for most of
SLO County, especially the northern part but it should be a dry
and fairly warm day in the south with highs jumping up in the 70s
under a fairly balmy tropical air mass.

As the main upper low approaches the Pacific NW coast it will
drive the moisture plume back south Sunday night into Monday with
the added benefit of a merging cold front and some jet dynamics as
well. So while the duration of this particular rain event will be
considerably shorter, rainfall intensities, especially south of Pt
Conception will be quite a bit higher than what we will see
Saturday. At best it might reach the lower end of the criteria for
burn area problems but at this point given the short duration and
slightly lower rainfall numbers in the models the likelihood is
that rates won't reach criteria. There is a little bit of
instability with the front though so a thunderstorm or two can't
be ruled out. Overall rain numbers still look reasonable, .5" to
1.5" with slightly higher totals possible in NW SLO county and on
south facing slopes.

Snow not expected to be a factor with either system as snow levels
will be above 9000' for most of the event. They will come down
Monday afternoon and a couple inches of snow are possible at the
tail end of the event above about 6000'.

.LONG TERM...(TUE-FRI)

Tuesday will be mostly in between storms, though the next one
should bring some light precip to the Central Coast by afternoon.
This system will drop south Wednesday and models in good agreement
showing at least some precipitation all areas so pops were
increased. Doesn't look like a major storm but enough to continue
the wet pattern. Models handle the next system quite a bit
differently but it does look likely most areas will see some
additional precip Thu and/or Fri.

&&

.AVIATION...06/1800Z...

At 1800Z, around LAX...A deep moist layer around 4000 ft deep
with a weak inversion to 5000 ft.

Generally, VFR conditions are expected today with a good level of
confidence. A few MVFR ceilings are briefly possible around KLGB
for a few hours. Otherwise, the main story will be a deterioration
in conditions on Saturday as a weather system brings increasing
clouds, occasional rain, and low level east flow to the area
including KLAX.

KLAX...Good confidence in the 18z TAFS. Mostly VFR conditions
today, followed by MVFR to IFR conditions and low level east flow
on Saturday.

KBUR...Good confidence in the 18z TAF. Mostly VFR conditions today
followed by MVFR to IFR conditions Saturday with occasional rain.

&&

.MARINE...06/200 PM...

For the Outer Waters, Winds will remain below SCA level through
today. On Saturday and Sunday, southerly winds will increase with
the high likelihood of a 70% chance of Gale Force wind
gusts and a Gale Warning will be issued for the two northern
outer zones...west and northwest of Point Conception. There will
be a 50% chance that zone PZZ676 will need a SCA. Strongest
southerly winds will occur across the northern portion of the zone
by Saturday morning.

For the Inner Waters...SCA winds expected for pzz650 and pzz645
as the next front crosses the waters Saturday through Sunday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Gale Watch in effect from Saturday morning through late
      Saturday night for zones 670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(MON-FRI)
There is a small potential for mud and debris flows near burn
areas Sunday night into Monday morning as moderate to heavy rain
moves through the area. There is also the potential for roadway
flooding as well as rock and mudslides, especially San Luis Obispo
County. Additional storms are expected later in the week but
timing and strength too uncertain to determine hazard potential.

&&

PUBLIC...MW
AVIATION...Sweet
MARINE...Sweet
SYNOPSIS...Munroe

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