Southwest California area forecast discussion
National Weather Service Los Angeles/Oxnard California
455 am PDT Wednesday Jun 19 2013
..updated aviation discussion...
Synopsis...
A weak trough of low pressure aloft to the north of the state will
continue to produce a northerly pressure difference across the
state through Thursday. Gusty winds will continue across portions
of southwest California through late tonight. Onshore flow and a
cooling trend should develop for late week and into the weekend.
A warming trend could develop next week as upper-level high
pressure builds west.
&&
Short term (today-friday)...
A northerly surface pressure gradient remains over the state this
morning from a trough of low pressure over the Pacific northwest.
A series of weak boundaries continue to move south re-enforcing
the northerly surface gradient. Gusty winds continue across the
mountains...desert...and southern Santa Barbara County this
morning. A Wind Advisory has been extended for these areas this
morning into at least this evening...and some advisories may need
to be extended beyond the expiration time this evening. With the
northerly surface pressure gradient...compressional heating will
take place over South Coast basin bringing a slight warm-up in
temperatures through Thursday. Fog product imagery indicate the
marine layer confined to the central coast and southern Los
Angeles County this morning...and not much change should occur
between tonight and Thursday.
NAM-WRF and local 4-km WRF solutions start to weaken the northerly
surface gradient tonight and the low-level northwest flow over
the coastal waters should permit a more favorable eddy circulation
to develop between Thursday morning and Friday. There is a chance
that the marine layer coverage could be a little more expansive
tonight over Los Angeles County...spreading farther north...if the
northerly surface gradient breaks down more quickly and allows for
the the eddy circulation to slide northwest into a more favorable
position. Higher confidence exists for a deepening marine layer
and stronger eddy circulation from Thursday night through weekend
as the trough axis inches closer to the region.
Long term (saturday-tuesday)...
A deeper marine layer and another weak disturbance brushing the
area should allow for onshore flow to increase and bring a cooling
trend through the weekend. Marine layer coverage was expanded over
the previous package and the mixed layer cooled.
GFS model trends suggest a warming trend developing for the
middle of next week...and if operational GFS solutions verify...a
Summer weather pattern will take hold over the area for late next
week. Temperatures have been warmed in the package...but if the
model trends continue...temperatures may have be warmed further
than the current forecast.
&&
Aviation...19/0500z.
High confidence with 12z taf package. VFR conditions will persist at
most terminals except for 20 percent chance for IFR conds at ksmx
through 16z. 20 percent chance that MVFR ceilings will not materialize
at lax between 12z and 15z this morning. High confidence for VFR
conds for all sites...except 30 percent chance for MVFR visibilities for
coastal sites tonight after 06z.
Klax...VFR conditions will persist through 10z Thursday. With 30
percent chance for MVFR conds after that through 17z.
Kbur...VFR conditions are expected throughout the period.
&&
Lox watches/warnings/advisories...
red flag warning (see laxrfwlox).
Gale Warning (see laxmwwlox).
Wind Advisory (see laxnpwlox).
Small Craft Advisory (see laxmwwlox).
High rip current risk (see laxsrflox).
&&
$$
Public...Hall
aviation...ck
fire weather gomberg/Hall
synopsis...Hall
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