019 
FXUS66 KLOX 121747
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 
947 AM PST Sun Feb 12 2017

.SYNOPSIS...
Gusty offshore winds will affect the area today and to a lesser
extent Monday. High temps will be above normal today and Monday. 
Another storm will approach from the north by late Thursday into 
Friday.

&&

.MORNING UPDATE...
Latest visible satellite imagery indicated mostly clear skies 
across the forecast area. The one exception was across the 
leeward side of the eastern San Gabriel Mtns and the Antelope 
Valley where a cumulus deck around 8000 ft continues to linger due
to the NE flow at the mid levels thanks to the upper low off the 
coast of Baja this morning. Not expecting any showers to develop 
as most the air mass is stable. The main weather issue today will 
be the offshore winds that are already occurring across these same
mountains. In fact a High Wind Warning is in place through mid
afternoon and already meeting criteria with gusts as high as 71 
mph at Camp Nine and 62 mph at Chilao in the San Gabriel Mtns. The
offshore winds have not become more widespread and surfaced down 
to the the wind prone valleys and coastal passes and canyons so 
far this morning. Still expecting winds to surface later this 
morning in most wind prone Santa Ana wind locations. One of the 
reasons winds have been late to get going is that the LAX-DAG sfc
gradients were not too impressive this morning at only -2.3 mb. 
There seems to be a stronger northerly component still this 
morning. The stronger winds across the San Gabriel Mtns makes 
sense due to the upper support due to the location of the upper 
low. So winds around the low are able to affect the higher 
terrain with plenty of subsidence at that level. Will continue 
with the wind advisories for now and leave high wind warnings in 
place as they are already verifying well.

One caveat to the winds, if they do not develop across the Valleys
and coast, then high temps could end up being a few degrees cooler
than forecasted but still warmer compared to yesterday. 

***From Previous Discussion***
&&

.SHORT TERM...(TDY-TUE)

The upper level flow in between the departing upper low and the 
approaching ridge is from the north now and will transition to the
NE later this morning. The current gradient to KDAG is an 
unimpressive +.1 MB which explains why all of the winds are 
confined to the mtns. The offshore flow and the upper level winds 
will peak this morning and advisory level gusts will develop. Not 
100 percent sure if the high wind warning gusts will develop 
anywhere except for Whittaker peak but there still is a chance. 
Otherwise today will be sunny (save for the morning mtn clouds) 
with rising hgts and offshore flow conspiring to bring 4 to 8 
degrees of warming to the coasts and vlys with most temps a couple
degrees above normal.

Offshore flow will prevail on Monday but without the upper support
so while there will be some morning canyon winds but they will be
below advisory level. There will be several more degrees of
warming.

The ridge gets knocked down on Monday night. An eddy will develop
as offshore flow turns onshore. This should bring marine layer
stratus to LA and VTA county coast as the as the San Gabriel vly.

Tuesday will be sunny after the stratus dissipates, The lower 
hgts and onshore flow will kick off a cooling trend...most 
prominent across the LA/VTA coast.

.LONG TERM...(WED-SAT)

A quick hitting ridge and burst of offshore flow will hit the area
Wednesday. There will likely be enough mid and high level clouds
sailing through the ridge to call it a partly cloudy day. Still
the higher hgts and offshore flow will create a nice bump up in
temps and will put Wednesday in contention with Monday for the
warmest of the next 7.

All of that changes of Thursday as it looks like the storm gates
are going to open up again. The mdls are struggling to come up
with a consistent solution for the storms from Thu to Sun. The
most certain aspect of the period is Thursday when it looks pretty
likely that a weakening cold front will bring rain to the central
coast in the afternoon and then to the rest of the area overngiht.

As for Friday through Sunday...there will be series of trofs. The
GFS is very wet through this period and brings a major 72 hour
rain event to the area. The EC agrees that there will be periods
of rain but with much lower rainfall totals.

&&

.AVIATION...12/1630Z...

At 1615Z, there was no marine inversion at KLAX.

Overall, high confidence in 18Z TAF package as offshore flow will
keep all sites VFR through the TAF period. The offshore winds will
be strongest across Ventura/LA counties today and some LLWS and
MDT UDDFs will be possible through early this afternoon. 

KLAX...high confidence in 18Z TAF. VFR conditions will persist
through the TAF period. Light easterly winds will continue into
early this afternoon, but are expected to remain below 7 knots.

KBUR...high confidence in 18Z TAF. VFR conditions will persist
through the TAF period. With offshore flow, LLWS and turbulence
will be likely through mid-afternoon.

&&

.MARINE...12/830 AM...

For the Outer Waters, moderate to high confidence in current
forecast. High confidence in winds dropping below Small Craft 
Advisory (SCA) levels this morning and remaining below SCA levels
through Wednesday (although there is a 20% chance of SCA level
winds developing again Monday afternoon/evening). On Thursday,
winds will shift to the south and increase, possibly reaching SCA
levels.

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, winds and seas are expected to
remain below SCA through Wednesday. On Thursday, there is a chance
of SCA level southerly winds developing along with a west swell
approaching 10 feet. For the waters south of Point Conception,
moderate confidence in SCA level northeast winds this morning
through early afternoon from Point Mugu south to Santa Monica and
across the San Pedro Channel. Otherwise, winds and seas are
expected to remain below SCA levels through Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 2 PM PST this afternoon for
      zones 41-44>46-88-547. (See LAXNPWLOX).
     High Wind Warning in effect until 2 PM PST this afternoon for
      zones 53-54. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until noon PST today for zone
      655. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(TUE-SAT)
Rain is possible later Thursday. Heavier rain is possible later
Friday and Saturday.

&&

$$

PUBLIC...Kaplan/Rorke
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Sweet

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