Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 291154
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
454 AM PDT Wed Mar 29 2017

New Aviation Discussion

.SYNOPSIS...
High pressure and gusty offshore winds will make for a warm day
today. A trough of low pressure will bring cooler conditions for
Thursday and Friday with another round of strong and gusty
northerly winds. Warmer conditions will likely return this weekend
as high pressure builds into the region, and weak offshore flow
returns. Cooling is expected early next week as a trough moves
into the West Coast

&&

.SHORT TERM...(TDY-FRI)

Clear skies across the region early this morning, with a sunny day
expected. Gusty winds have developed in the mountains, but winds
so far were only localized in the valleys. Will leave the wind
advisories in place for now, since winds could increase toward
sunrise with the modest amount of lingering upper support across
the region. Otherwise, rising heights and thicknesses and warming
at 850 and 950 mb will likely result in significant warming across
the region, with highs well into the 80s to around 90 in the
valleys. Record high temps are possible today since daily records
are rather low.

The ridge axis will move east of the region later today, then an
upper level trough will move into the Pac NW tonight and early
Thu. It will then close off into an upper low as it moves into
the Great Basin Thu afternoon. The WRF shows an eddy circulation
across the inner waters tonight, and it is possible that some low
clouds/fog could push into coastal sections of L.A. County late
tonight and Thu morning, but at this point, that seems like a low
probability. Similarly, some low clouds could also develop on the
Central Coast.

A dry frontal system will move through northern sections of the
forecast area Thu. Strengthening winds aloft and a good area of
subsidence will overspread the region during the day. Gusty west
to northwest winds should develop in the mountains, in the
Antelope Valley and on the Central Coast during the afternoon, and
winds will likely reach advisory levels in these areas. Max temps
should be down 8 to 12 degrees in most areas on Thu.

The upper low will drift east southeastward Thu night, reaching
the Four Corners area Fri morning. Strong northwest winds at 700
and 850 mb, and decent subsidence will likely bring widespread
advisory level northwest to north winds Thu night, transitioning
to a more nely direction Fri morning. This wind event looks quite
similar to that which occurred Mon night and Tue morning, though
perhaps a bit less strong. The winds will drop off across the
Central Coast Thu evening, but elsewhere, expect advisory levels
winds across the mtns and south coast of SBA County, the mtns of
L.A. and VTU Counties, the Santa Clarita Valley, much of the San
Fernando Valley and the valleys of VTU County, the Los Angeles
County coast below passes and canyons from Malibu to the Hollywood
Hills and the Westside of Los Angeles. There may be some High
Wind Warning level gusts in the mtns, but it looks as though those
will be localized.

There will likely be some low clouds on northern and interior
slopes as northerly upslope flow pushes into those areas, but
do not expect any precipitation. Winds will diminish in most
areas Fri afternoon. Max temps on Fri should be similar to those
on Thu, or perhaps down a couple of degrees in some areas.

.LONG TERM...(SAT-TUE)

An upper ridge will build into the region Sat, causing heights and
thicknesses to rise. Offshore low level flow will continue, with
some gusty winds, but below advisory levels. Expect significant
warming across the region Sat, with temps back into at least the
lower 80s in the valleys. A trough will approach with West Coast
Sunday, and low level flow will turn onshore. Expect a few degrees
of cooling, especially across the coastal plain.

The trough will move through the West Coast north of the forecast
area, then into the Great Basin Monday, likely bringing a bit
more cooling to the region. However, the GFS now shows a weaker
system than it showed on last night`s run, so cooling will be less
dramatic, and there is no longer a chance of rain. The trough will
move into the Rockies and southern plains states on Tue. A broad
wnw flow pattern will set up across the region, with heights rising
slightly, and only minor changes in max temps expected.

&&

.AVIATION...29/1200Z

At 08Z, there was no marine layer at KLAX. There was a sfc based
inversion with a top of 1000 feet and max temp of 21 degrees C.

High confidence in the current forecast through 09Z. There is a 40
percent chc of IFR cig/vis at KLGB...KLAX and KSMO after 09Z.

KLAX...High confidence in the current forecast through 09Z. There is a 40
percent chc of IFR cig/vis after 09Z.

KBUR...High confidence in the current forecast.

&&

.MARINE...29/300 AM

Across the Outer Waters...A combination of winds and seas will
keep Small Craft Advisory conditions through at least Thursday
morning. Gale force winds are possible Thursday afternoon through
Friday.

Across the Inner Waters... Strong SCA winds will affect the
western portions of the inner waters on Thursday and Friday with a
20 percent chc of gale force winds.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 2 PM PDT this afternoon
      for zones 34-35. (See LAXCFWLOX).
     Beach Hazards Statement in effect until 3 PM PDT this
      afternoon for zones 40-41-87. (See LAXCFWLOX).
     Wind Advisory in effect until 2 PM PDT this afternoon for
      zones 44>46-53-54-88-547. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 PM PDT Friday for zone
      645. (See LAXMWWLOX).
     Small Craft Advisory for hazardous seas in effect until 9 AM
      PDT this morning for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 1 PM PDT Thursday for
      zones 670-673-676. (See LAXMWWLOX).
     Gale Watch in effect from Thursday afternoon through Friday
      afternoon for zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(FRI-TUE)
Gusty north winds will affect portions of the region Friday
morning.

&&

$$

PUBLIC...DB
AVIATION...ASR
MARINE...Rorke
SYNOPSIS...DB

weather.gov/losangeles



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