Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 282201
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
301 PM PDT SAT MAY 28 2016

.SYNOPSIS...

Weak low pressure will continue the below normal temperatures,
along with a slight chance of afternoon and evening thunderstorms
across mountains and some interior valleys through Sunday. There
will be overnight through morning low clouds through at least
Monday. High pressure will build in Tuesday and peak on Thursday
with above normal temperatures.

&&

.SHORT TERM...(TDY-TUE)

Plenty of pop-up cu developed this morning into the early afternoon
over the mtns and Antelope Vly. By 230 PM, a thunderstorm had
developed over the SBA County mtns, with a few showers noted over
the VTU County mtns. There is enough instability and moisture in
place for further isolated thunderstorms to develop in the mtns and
Antelope Vly thru the afternoon and early evening as a weak upper
level trof lingers nearby. Any thunderstorms that develop would be
capable of producing brief heavy rain, small hail, gusty winds and
dangerous cloud-to-ground lightning. Any shower or thunderstorm
activity should dissipate around or shortly after sunset.

Low clouds have been stubborn early this afternoon along portions of
the Central Coast, SBA s coast and portions of the VTU/L.A. County
coasts. Current satellite trends would suggest the low clouds will
persist thru the rest of the afternoon into early this evening. The
low clouds are then expected to quickly expand along the coast and
inland tonight to the adjacent vlys. Low clouds are also expected to
develop in the Salinas River Valley late tonight. Otherwise, mostly
clear skies should prevail for much of the forecast area thru
tonight.

A weak upper level low over the Central Coast this afternoon will
drift se across the forecast area tonight and Sun morning, then into
sern CA for Sun afternoon. An e-w oriented upper level trof will
linger over srn ca Sun night and Mon, while at the same time upper
level ridging builds into central and nrn CA. The upper ridge will
expand into swrn ca Mon night and Tue.

The marine layer pattern will continue over the next few days, with
the inversion forecast to gradually strengthen and lower each day,
most pronounced Mon night and Tue as the upper ridge builds in and
boundary layer temps warm up. Extensive night and morning low clouds
and fog can be expected to affect the coast and adjacent vlys
tonight thru Tue morning, altho the inland extent of the low clouds
will diminish considerably Mon night due to the shrinking marine
inversion. There will be the possibility of afternoon cu buildups in
the mtns Sun thru Mon, but for Sun there should continue to be
enough moisture and instability for the formation of isolated
showers or thunderstorms in far sern SLO County, Cuyama Vly, the
mtns of SBA/VTU/L.A. Counties and in the Antelope Vly. Any
thunderstorms that develop could drift s into the adjacent vlys over
VTU/L.A. Counties as well by late Sun afternoon or early evening.
The 12Z NAM does indicate the best chance of thunderstorms Sun
afternoon to be over eastern San Gabriel Mtns, but even so a slight
chance of showers and thunderstorms is in the forecast for all of
the above mentioned areas. Otherwise, mostly clear skies are
expected over the forecast area for the most part Sun thru Tue. A
typical onshore flow pattern is expected each afternoon and evening,
with locally gusty sw to nw winds for the foothills, mtns and
Antelope Vly.

Temps for Sun are forecast to be generally 3 to 6 deg below normal
for the cst and adjacent vlys, while inland vlys, mtns and deserts
will be near normal to slightly above seasonal norms. For Mon, temps
will warm a few degrees, especially in the interior areas, mtns and
deserts, where highs should be 4 to 10 deg above normal. For the
coastal plain, Santa Ynez Vly, and vlys of VTU/L.A. Counties, highs
on Mon will be 2 to 6 deg below normal overall. It`ll be warmer
still for Tue with many areas away from the coastal plain warming to
4 to 12 deg above normal. Highs in the warmest vlys on Tue should
reach the upper 80s to mid 90s.

.LONG TERM...(WED-SAT)

The EC and GFS are in decent agreement Wed and Thu with upper
ridging over the area. For Fri and Sat, the EC keeps the fcst area
on the w side of a large upper ridge, while the GFS brings a broad
upper trof to the CA cst Fri, then upper troffiness moves over the
area thru Sat while a weak upper low swings into nrn Baja from the e
Pac. Either solution will keep dry and warm conditions over swrn CA
thru the extended period. Night and morning marine layer clouds will
continue to affect mainly coastal areas Wed, then be confined to the
L.A. County coast Thu thru Sat. Otherwise, mostly clear skies will
prevail across the region Wed thru Sat. There will continue to be
typical onshore flow afternoon and evening hours, with locally gusty
sw to nw winds in the foothills, mtns and deserts.

Temps will warm to about 5 to 12 deg above normal for many areas
away from the coastal plain Wed thru Fri, with slight cooling
expected on Sat. The warmest days should be Thu and Fri, with highs
in the warmest vlys and foothills reaching the upper 80s to mid 90s,
except mid to upper 90s in the Antelope Vly.

&&

.AVIATION...28/12Z.

Upper level low over the coastal waters north of Point Conception
will shift east and a ridge of high pressure upstream will
approach the area while a mid level low centered south of the
area shifts east. Upper level light west winds will become light
to moderate northwest and mid level light southeast winds will
become light east-northeast after 29/17z. Isolated thunderstorms
are possible over the Santa barbara...Ventura and Los Angeles
county mountains between 28/21-29/03z. Thunderstorm tops 36kft and
will move east-northeast 10 kt. Weak to moderate onshore pressure
gradient through 29/03z and after 29/20z otherwise Catalina eddy
will develop. Capping inversion was 1kft at VBG and 2.4kft at LAX
this morning and is expected to differ little Sunday with
organized low cloud field.

Marine layer at LAX at 1600Z is 2477 feet deep and the inversion
top is at 3510 feet with a temp of 15.1 degrees C.

KLAX...Chance cigs 019-022 through 28/21z then chance 015-020
between 29/03-29/20z.

KBUR...Chance cigs 010 after 29/08z.

virtually certain - 95-100%
very likely       - 80-95%
likely            - 60-80%
chance            - 30-60%
very unlikely     - 20% OR LESS

&&

.MARINE...28/200 PM PDT.

Small craft advisory conditions are not expected through
Thursday. Otherwise a Catalina eddy is expected to develop each
night over the bight through Thursday and northwest winds are
expected elsewhere and fill in the bight each afternoon. A complex
storm systems over the Southern Ocean last Monday and Tuesday
with a fetch oriented 190-210 degrees from Ventura generated
swells that will arrive Monday and build through Wednesday. The
swells will remain below small craft advisory for hazardous sea
conditions but there will be extra surging and currents along
exposed south facing shores. In the meantime a small south swell
will continue and a locally generated swell from 310-330 degrees
will subside tonight.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...Sirard
AVIATION...30
MARINE...30
SYNOPSIS...Bartling

weather.gov/losangeles



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