Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 121131

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
331 AM PST Tue Dec 12 2017

Gusty offshore winds, warm afternoon temperatures, and dry
conditions will persist through the week. Smoke from the fires
will impact regional air quality through the week as well.



A sloppy rex block will persist over the west coast for the next
three days which will result in very similar day to day weather.

582 hgts with continuous weak offshore flow will give the area
three consecutive days with max temps 10 to 15 degrees above
normal. Day to day temps changes will be no more than a couple of
degrees in either direction except for areas that see a
substantial change in smoke layer coverage.

Min temps also will change little each day and will be below
normal in the wind sheltered locations.

There is moderate offshore flow from the north which is 2 MB
stronger than it was last night. Somewhat surprisingly and
fortunately this increased push has not resulted in much if any
increase in the north winds esp for the SBA south coast. Further
good news is that the north gradients will relax over the next
few days and will greatly reduce the risk of north winds.
Otherwise just look for east to northeast morning winds 15 to 25
mph with perhaps a few 35 mph gusts.


The EC and the GFS do not agree in the long term. The EC soln is
new and very different and while it would be nice to believe its
wetter forecast think it is an anomalous run and have discounted
it. Prefer and used the GFS for the extended forecast.

The GFS brings an inside slider down through the CA/NV line on
Friday. The gradients will turn onshore during the day and hgts
will fall. Temps will cool but will still be above normal.

The new soln of the GFS brings in a little more cool air than
previous mdls if this is true max temps on Saturday will need an
additional 2 4 degrees of cooling. Either way Saturday should be
the coolest day of the next 7. The other concern with the new
solution would be north winds. The additional cold air advection
would bring stronger north winds to the area including the SBA
south coast. This part of the forecast will need close monitoring
for potential fire wx impacts.

The look for two more days Sunday/Monday of weak Santa Anas with
a warming trend and unfortunately an increase in fire risk.



At 1049Z, around KLAX, there was no marine layer. However, there
was a surface inversion with the top of the inversion at 220 ft.
with the temperature at 23 degrees Celsius.

VFR conditions are expected throughout the period, except for a
chance of MVFR conditions in smoke at coastal and valley
terminals. Best chance across SBA/VTU Counties. Periods of
weak low-level wind shear and turbulence are possible Ventura
County terminals through 20z today.

KLAX...VFR conditions are expected throughout the period. There is
a 30 percent chance of MVFR conditions in smoke from 22z-06Z. Any
east winds should remain less than 7 knots.

KBUR...VFR conditions are expected throughout the period. No wind
issues are expected at this time. 20% chance for MVFR vsbys from
smoke late this afternoon into this eve.


.MARINE...12/230 AM.

For the Inner Waters south of Point Conception, winds will remain
below SCA strength through Thursday. There will be local NE winds
nearshore from Ventura to Malibu and S of Palos Verdes Peninsula
across the San Pedro Channel each morning into the early afternoon

The near shore waters north of Point Sal will remain below SCA
level through at least early Friday.

Elsewhere, winds and seas are expected to remain below Small
Craft Advisory levels through Thursday, and then rise to SCA level
from the northwest on Friday. There is a 30 percent chance of Gale
level winds for the Outer Waters North of Point Conception
sometime Friday or Saturday.

There will be areas of smoke from the Thomas fire over portions
of the Coastal Waters, mainly from the waters west of Ventura
County through the Santa Barbara Channel and over the outer
waters. Local visibilities could possibly drop to near one
nautical mile or lower at times.


CA...Red Flag Warning in effect until 8 PM PST this evening for
      zones 240-244>246-288. (See LAXRFWLOX).
     Red Flag Warning in effect until 8 PM PST Wednesday for zones
      253-254. (See LAXRFWLOX).


Critical fire weather conditions possible Thursday with light
offshore winds and single digit humidities.



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