Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 191228
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
428 AM PST Sun Feb 19 2017

...Aviation discussion updated...

.SYNOPSIS...

A wet and cool weather pattern will resume tonight and persist
through Wednesday as a series of low pressure systems move into
the West Coast. Highest rainfall totals are expected to be north
of Point Conception. Drier weather is expected late in the week,
then another storm may bring more rain to the region next weekend.

&&

.SHORT TERM...(TDY-TUE)

Abundant low level moisture and cloud cover across the forecast
areas early this morning. Gusty nw to n winds across southern
Santa Barbara County have decreased, so Wind Advisories have been
allowed to expire. There were a few sprinkles or light showers on
northern slopes early this morning, and these may persist through
the morning. Precip amounts will be very light. Models show a lot
of moisture lingering through the day. There will likely be some
partial clearing today, especially south of Pt Conception. For the
most part, skies will vary from partly to mostly cloudy from late
morning through the afternoon, except probably just mostly cloudy
north of Point Conception. Max temps may be up a couple of degrees
in some areas today, but will still be below normal.

Very weak ridge across the region will continue to collapse sewd
today as a large upper trough moves into the northeast Pacific
and a strong jet takes aim at northern California. An increasingly
deep band of moisture with some decent mid level lift will sag
southward down the West Coast later today and tonight, and low
level southerly flow will increase. As this occurs, there will
be an increasing chance of rain later today in areas north of Pt
Conception, especially across northern SLO County. Rain will
develop across SLO and SBA counties this evening, and will become
likely across VTU and much of L.A. Counties overnight. Some of
the rain may be locally heavy across SLO county, particularly in
the higher terrain of northwestern SLO County, where there will be
some good orographic enhancement of the rainfall. Rain is expected
to be much lighter south of Pt Conception, especially across L.A.
County as this band of rain loses its punch as dynamics decrease
late tonight and early Monday. This first slug of moisture will
exit the region Monday morning, but skies should remain cloudy
and there will be a chance of showers through the day. It will be
another cool day across the region.

Another band of moisture will sag southward into the region from
northern and central CA late Mon or Mon night and linger into
Tue. This will be very similar to what occurs tonight and Mon
morning, with the heaviest rain and best moisture and dynamics
remaining across SLO and SBA Counties, Still, most areas should
have measurable rain Mon night into Tue, but amounts across VTU
and L.A. Counties are expected to be on the light side.
South winds could get close to advisory levels across portions of
SLO and SBA Counties at times late tonight thorough early Tue.

Overall, rainfall totals through Tue are expected to average
one half inch to one inch across SLO and SBA Counties, except
1-2 inches in the mountains, and possibly up to 3 inches across
the higher terrain of nwrn SLO County. Across VTU County, expect
one third to two thirds of an inch of rain, with up to 1.5 inches
in the western mountains. Across L.A. County rainfall totals
should be one tenth to one third of an inch, with local totals
up to an inch possible in the mountains. Snow levels will be
rather high through at least early Tue, so at this point, just
expect a few inches of snow at resort levels.

.LONG TERM...(WED-SAT)

Another system will move through central California on
Wednesday, bringing a chance of rain to the entire region, but
especially across SLo and SBA Counties. Thu and Fri look to be
dry, but still cool. Another storm system may bring rain to the
region by late Sat, and this system could be stronger, and bring
more significant rain to the entire region.

&&

.AVIATION...19/12Z.

At 08Z at KLAX... there was no notable inversion.

Overall... Moderate confidence in the current TAFs. Confidence is
reduced primarily due to uncertainty in the timing of the next
storm. IFR/MVFR conditions at the coastal and coastal adjacent
terminals of Los Angeles County and MVFR/VFR conditions across
the other coastal terminals through 17z-19z. There is a thirty
percent chance of IFR/MVFR conditions at all sites ahead of the
arrival of the precipitation... after 01z in San Luis Obispo
County and after 05z by the time it reaches Los Angeles County.
Otherwise and elsewhere VFR conditions will prevail.

KLAX... Moderate confidence in the current TAF. Confidence is
reduced primarily due to uncertainty in the timing of the next
storm. IFR/MVFR conditions through 17z-19z with a thirty percent
chance that conditions could linger longer. There is a thirty
percent chance of IFR/MVFR conditions after 05z ahead of the
incoming precipitation then IFR/MVFR conditions by 09z. East
winds 7 kt or less through 20z. Otherwise VFR conditions will
prevail.

KBUR... Moderate confidence in the current TAF. Confidence is
reduced primarily due to uncertainty in the timing of the next
storm. IFR/MVFR conditions through 17z-19z with a twenty percent
chance that conditions could linger longer. There is a thirty
percent chance of IFR/MVFR conditions after 05z ahead of the
incoming precipitation then IFR/MVFR conditions by 09z. Otherwise
VFR conditions will prevail.

&&

.MARINE...19/230 AM.

Outer Waters... an area of gale force winds over the central and
southern outer waters will slowly subside with gales ending by
10 AM over the waters near San Nicolas Island. A large long period
westerly swell currently over the outer waters will gradually
subside through tonight. Small Craft Advisory (SCA) level winds
are likely to persist over the outer waters through Monday
night... increasing again Wednesday into Thursday with gales
possible.

Inner waters... SCA winds and seas will affect much of the inner
waters through this afternoon. Sub-SCA conditions are likely on
Monday and Tuesday with SCA winds developing again on Wednesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 10 PM PST this evening for
      zones 34-35-39>41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 PM PST this afternoon
      for zones 645-650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PST Monday for zone
      670. (See LAXMWWLOX).
     Gale Warning in effect until 10 AM PST this morning for zone
      676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
Light to moderate rain with gusty winds are expected Tuesday and
Wednesday which will create hazardous roadway conditions. More
rain is possible on Saturday and it will likely be windy.

&&

$$

PUBLIC...DB
AVIATION...Kj
MARINE...Kj
SYNOPSIS...DB

weather.gov/losangeles


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