Small Craft Advisory 15, NWS Los Angeles, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1039 AM PST Sun Jan 22 2017

.SYNOPSIS...
There will be precipitation...heavy at times...and gusty winds into
this afternoon. This evening the rain will turn to showers...with
a chance of thunderstorms and gusty winds into Monday. There
may still be a chance of showers on Tuesday. The temperatures
should stay below normal into midweek. The skies will become fair
by midweek with normal temperatures on Friday and Saturday.

&&

.SHORT TERM...(TDY-TUE)

Rain is falling over most of the area with the exception of the
Antelope Valley area right now. Skies are mostly cloudy and there
are windy conditions above 2000 feet as well as along the SBA Co
central coast. One quarter to one half inch rainfall amounts in
the last six hours are common in SLO, SBA and VEN Co with a tenth
to a quarter inch in LA Co so far. Winds greater than 50mph along
I5 Grapevine also reported this morning.

*** From previous discussion ***

Satellite shows a textbook powerful winter storm with a cold low
to the west of Oregon with an occluded front wrapped around it and
extending into Oregon. From the occlusion a cold and a warm front
split off. The cold front extends from Modoc county to the Bay and
then out to the SW over the east Pac. Behind the front there is
plenty of convective open cell cu with a few lightning strikes.

The 06Z GFS and NAM runs remain in remarkably good agreement with each
other and are consistent with their previous runs. The forecast has
not been changed must at all. This will be the most significant storm
system for Southwestern California.

The heaviest rains associated with the main cold front will likely
affect SLO County between 5 AM and 1 PM, SBA County between 7 AM
and 3 PM, Ventura County between 9 AM and 5 PM and Los Angeles
County between 11 AM and 8 PM.

Just ahead of the front there will be a period of gusty se to s
winds across much of the region. Wind advisories have been expand
to include most all of the coastal and valley areas south of Point
Conception save for the San Gabriel. Gusty west winds behind the
front will likely affect coastal sections of LA/VTA Counties tonight.

The models do not show a great deal of instability with this
system. But there is a serious amount of jet energy and while the
chc of TSTMs is under 20 percent it is not zero either. There is a
better chc of TSTMs Monday.

Rain amounts will likely be 2-4 coast/valleys (highest near the
foothills), 3-6 foothills/mtns. Would not be surprised to see more
rain in the foothills above the city of Santa Barbara and the San
Gabriel Mtn Cstl Slopes. Peak hourly rainfall rates will be in
the 1-1.5" range (mainly south of Pt Conception due to the better
orographics)Rates this are capable of producing flash flooding
not only in the burn areas but across the entire forecast area
south of Pt Conception where a flash flood watch is in effect.

This is a special storm due to three factors. There is a 160-170kt
jet that will align itself parallel to the front which will slow
it down and intensify the from (rather than the usual
perpendicular jet to front orientation that shoots the front into
and through the area in just a few hours) This intense jet driven
storm will also be working with an impressive 1.2 to 1.4 inch
precipitable water column. Finally, a 8mb LAX to BFL onshore will
develop and this will bring very strong south sfc winds to the
area which will greatly enhance the rainfall on the south facing
slopes.

Snow levels will rise quickly to 8000 feet with the warm
southerly flow. They will then fall just as quickly this evening
in the wake of the cold front. Available moisture drops off
significantly but there will still be enough moisture to combine
with the colder air to generate decent snowfall amounts across
the mountains. A winter storm warning will go into effect just as
the high wind warning expires early this evening. Snow levels
will fall to between 4000 and 5000 ft by late tonight and continue
near there through Monday. These low snow levels will bring some
snow to the Grapevine but there will not be that much
accumulations.

Broad cold cyclonic flow will dominate the area on Monday. It will
be a showery day and the entire area will see some rainfall. The
rainfall with this storm will be much less homogeneous. The
atmosphere will be very unstable and there will be a slight chc of
TSTMs. These TSTMs will be able to put out some good rainfall
rates and another flash flood watch just for the burn areas may be
needed. It will be  very cool day with highs mostly in the 50s at
lower elevations and 20s/30s in the mountains.

On Tuesday the upper low that is spinning off of the Oregon coast
will become incorporated into a large scale trof rotating out of
Canada. The latest mdls are taking this system further to the west
than previous runs and it looks like the best chc of rain will be
over the outer waters.

.LONG TERM...(WED-SAT)

Both the GFS and EC agree at least in principle that east pac
ridging will build into the area Wednesday and remain through at
least the weekend. While it will almost certainly be dry the mdls
do not show much in the way of warming due to the large sfc cold
pool. There will be some warming over the weekend as the ridge
increases and the offshore flow increases.

&&

.AVIATION...22/18Z.

At 18z at KLAX...there was no marine inversion.

There is generally low confidence in the 18z TAFS. Frequent
changes in the ceiling heights and visibility will be the primary
concerns. The rain was starting to show some signs of slowing down
north of Point Conception...although scattered showers are likely
to continue through Monday. South of Point Conception...the areaof
heaviest rain will slowly translate from Ventura county into Los
Angeles county by late this afternoon.

KLAX...Low confidence in the TAF. The reduced confidence is
primarily due frequent changes in ceiling and visibility.
Conditions will range mostly from MVFR to IFR. Winds from 090-130
degrees greater than 7 kts will continue through 00z. There is a
forty percent chance of southerly cross winds greater than 20
knots 23Z-01Z. The winds are expected to shift around to 210-240
degrees after 02z. There is a thirty percent chance of
thunderstorms after 08z.

KBUR...Low confidence in the TAF. The reduced confidence is
primarily due frequent changes in ceiling and visibility.
Conditions will range mostly from MVFR to IFR. There is a thirty
percent chance of thunderstorms after 08z.

&&

.MARINE...22/900 AM.

Very dangerous sea conditions are expected today.

Breaking waves will continue over Morro Bay and Ventura Harbor
entrances as well as near the shoreline and breakwalls. There is
high confidence in a large swell through Tuesday but low
confidence on the timing of the swell heights.

High confidence for widespread gale force southerly winds and very
steep seas through midday for the northern waters and into the
evening for the southern waters. There is a thirty percent chance
that Gale Warning conditions across the southern waters may
continue into the overnight hours.

Moderate confidence in thunderstorms forming late tonight and
Monday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 6 PM PST Tuesday for zones
      34-35-39>41-87. (See LAXCFWLOX).
     Wind Advisory in effect until noon PST today for zones
      34>36-39. (See LAXNPWLOX).
     Wind Advisory in effect until 3 PM PST this afternoon for
      zones 37-38-40-41-44>46-51-87-88-547. (See LAXNPWLOX).
     Flash Flood Watch in effect until 2 PM PST this afternoon for
      zones 39-52. (See LAXFFALOX).
     Flash Flood Watch in effect until 4 PM PST this afternoon for
      zones 40-44-45-53. (See LAXFFALOX).
     Flash Flood Watch in effect until 8 PM PST this evening for
      zones 41-46-54-59-87-88-547. (See LAXFFALOX).
     High Wind Warning in effect until 7 PM PST this evening for
      zones 52>54-59. (See LAXNPWLOX).
     Winter Storm Warning in effect from 7 PM this evening to 6 PM
      PST Monday for zones 52>54. (See LAXWSWLOX).
PZ...Gale Warning in effect until noon PST today for zones
      645-670-673. (See LAXMWWLOX).
     Gale Warning in effect until 9 PM PST this evening for zones
      650-655-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
No significant hazards expected after Day 2. See the LOX
Watches/Warnings/Advisories for products concerning the current
storm.

&&

PUBLIC...ASR/Rorke
AVIATION...Sweet
MARINE...Sweet
SYNOPSIS...STU

weather.gov/losangeles

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1148 AM PST SUN JAN 22 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0910 AM     NON-TSTM WND GST CHATSWORTH              34.27N 118.59W
01/22/2017  M56 MPH          LOS ANGELES        CA   MESONET

            MESONET STATION CHATSWORTH /E1734/.

&&

NWS LOS ANGELES/OXNARD CA
IRIS SYSTEM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1149 AM PST SUN JAN 22 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1100 AM     NON-TSTM WND GST 13 NNW CUYAMA           35.10N 119.77W
01/22/2017  M59 MPH          SAN LUIS OBISPO    CA   MESONET

            MESONET STATION CARRIZO /CAZC1/.

&&

NWS LOS ANGELES/OXNARD CA
IRIS SYSTEM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1150 AM PST SUN JAN 22 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0922 AM     NON-TSTM WND GST 6 NE PYRAMID LAKE       34.74N 118.72W
01/22/2017  M60 MPH          LOS ANGELES        CA   ASOS

            ASOS STATION SANDBERG /SDB/.

&&

NWS LOS ANGELES/OXNARD CA
IRIS SYSTEM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1151 AM PST SUN JAN 22 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0906 AM     NON-TSTM WND GST 12 SW MIRANDA PINE MOUN 34.92N 120.18W
01/22/2017  M67 MPH          SANTA BARBARA      CA   MESONET

            MESONET STATION TEPUSQUET /TSQC1/.

&&

NWS LOS ANGELES/OXNARD CA
IRIS SYSTEM