Area Forecast Discussion
Issued by NWS Los Angeles, CA

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115
FXUS66 KLOX 310047
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
547 PM PDT SAT JUL 30 2016

.SYNOPSIS...

Monsoonal moisture will support a slight chance of thunderstorms over
the mountains and the Antelope Valley through early this evening.
Otherwise expect fair skies and a gradually cooling trend through
the week as a ridge of high pressure is slowly replaced by a
trough of low pressure. The low pressure may bring more widespread
coverage night to morning low clouds to coastal areas late next
week.

&&

.SHORT TERM...(TDY-TUE)

Areas of low clouds lingered over the SoCal bight to some of the
beaches and along and off portions of the Central Coast early this
afternoon. Varying amounts of low clouds should persist along the
coast both n and s of Pt Conception this afternoon into early
evening then expand overnight and move inland to some of the
adjacent vlys. Cu buildups were noted over the VTU/L.A. County mtns
early this afternoon, and there is a slight chance of thunderstorm
development in these areas thru early this evening, some of which
could drift n into the Antelope Vly. Otherwise, mostly clear skies
will prevail across the forecast area thru tonight. Good onshore
gradients (+9.0 mb LAX-DAG late this afternoon according to the 12Z
NAM) will result in gusty sub-advisory s to w winds into this
evening for the foothills, mtns and deserts. Temps this afternoon
are expected to be cooler than yesterday but still run several
degrees above normal. The warmest vlys and foothills are expected to
reach the mid 90s to around 100, except 103 to 106 in the Antelope
Vly.

Fairly strong upper level ridging will persist over srn CA thru Tue,
with 500 mb heights around 591 to 593 dm. 1000-500 mb thicknesses
will about 580 to 585 dm for Sun thru Tue. The marine inversion
which was about 1000 to 1300 ft deep this morning should gradually
increase to near 1500 ft thru Mon then remain around this level for
Tue. Very good onshore gradients are forecast by the NAM up to
around +9.0 mb LAX-DAG each afternoon.

Marine layer clouds and fog should expand along the coastal plain
and extend into some of the adjacent vlys night and morning hours
thru Tue. Afternoon clouds should also develop over the mtns and
deserts each day with marginal amounts of monsoonal moisture
filtering into the area from the e at mid levels. A 10 percent or
less chance of a thunderstorm cannot be ruled out as well in the
mtns and deserts for Sun and Mon, which is too small a chance to
mention in the zones. Otherwise, mostly clear skies will prevail
thru Tue across the forecast area. Gusty afternoon and evening s to
w winds will persist across the foothills, mtns and deserts during
the period. The onshore flow and gradually deeper marine layer will
help to lower temps some thru Sun, with little change in temps
expected Mon and Tue. Even so, highs will remain several degrees
above normal away from the coast. Highs for Sun thru Tue in the
warmest vlys and foothills will be in the upper 80s and 90s, except
100 to 104 in the Antelope Vly.

.LONG TERM...(WED-SAT)

EC/GFS in good generally agreement during the extended period, altho
minor differences start to show up on Sat. The upper ridging will
continue over srn CA on Wed. The ridging will weaken over the area
Thu, allowing an upper level trof to approach from the e Pac. This
upper trof will move into central and swrn CA for Fri. The GFS
builds an upper ridge back into the region for Sat, while the EC
lingers the upper troffiness over the area. Favored the GFS
fcst of a slightly more progressive movement of the upper trof. The
marine layer pattern will continue thru the week, with varying
amounts of night and morning low clouds and fog for the coast and
some adjacent vlys. Otherwise, mostly clear skies will prevail
across the region. Temps are forecast to be slightly above normal
Wed, then cool to near normal overall for Thu thru Sat.


&&

.AVIATION...31/0000Z.

At 00Z, the marine layer was around 1100 feet deep at KLAX. The
top of the inversion was near 4700 feet with a temperature around
26 degrees Celsius.

Moderate to high confidence in the current forecast, except low
confidence in Los Angeles County Valley terminals where there is
a chance the sites remain clear overnight. Coastal terminals will
see mainly in IFR to MVFR category, likely deteriorating to LIFR
north of Point Conception between 06Z and 15Z.

KLAX...MVFR conditions will spread in between 02Z and 06Z.
Conditions should remain MVFR but there is a 40 percent chance of
IFR conditions with an earlier arrival than forecast...and
possibly after 08Z. VFR conditions should develop around 17Z, but
there is a 20 percent chance that MVFR conditions could linger
until 20Z.

KBUR...There is a 60 percent chance of IFR conditions between 10Z
and 16Z. VFR conditions should develop between 15Z and 16Z.

&&

.MARINE...30/300 PM.

High confidence in the forecast through the weekend into early
next week. Winds will generally remain light to occasionally
moderate through the weekend...strongest over the outer waters.
There is a 30% chance that SCA level wind gusts could develop
near Point Conception to near San Nicolas Island Monday in the
late afternoon and evening. A small but long period southerly
swell will develop Sunday into Monday.


&&

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

&&

$$

PUBLIC...Sirard
AVIATION...Hall
MARINE...Smith
SYNOPSIS...Munroe

weather.gov/losangeles



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