871
fxus66 klox 121743
afdlox

area forecast discussion
national weather service los angeles/oxnard ca
943 am pst tue dec 12 2017

.synopsis...
a high and offshore winds will persist through friday for dry and
smokey conditions with above normal temperatures. the onshore flow
will bring a slight cooling trend on saturday. then offshore flow
will return next week for a warming trend.

&&

.short term...(tdy-thu)

another warm offshore flow day today with sub-advisory level santa
ana breezes. highs again 10-15 degrees above normal. very similar
scenario tomorrow, though slightly cooler as gradients trend
onshore in response to a weak inside slider moving into the great
basin during the afternoon. the one minor change noticed in the
models today vs. yesterday is a slightly stronger northeast push
thursday into friday behind that trough. this may push winds into
the advisory category for parts of la/ventura counties but still
not seeing any significant increase in winds across sb county in
the short term.

.long term...(fri-mon)

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.

&&

.aviation...12/1800z.

at 1700z, 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 22 degrees celsius.

vfr conditions are expected throughout the period, except for a
chance of mvfr conditions in smoke at some coastal and valley
terminals. best chance across sba/vtu counties. periods of
weak low-level wind shear and turbulence are possible through 20z
today.

klax...vfr conditions are expected throughout the period. there is
a 30 percent chance of mvfr conditions in smoke at times. 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 at times.

&&

.marine...12/900 am.

for the inner waters south of point conception, winds will remain
below sca strength through thursday. there will be local ne winds
near shore from ventura to malibu and s of palos verdes peninsula
across the san pedro channel each morning into the early afternoon
hours.

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.

&&

.fire weather...12/900 am.

the red flag warnings are unchanged. it remains in effect through
8 pm this evening for the ventura coasts, ventura valleys, the
santa clarita valley, and the santa monica mountains. it also
remains in effect through 8 pm wednesday for the los angeles and
ventura county interior mountains. these warnings may need to be
extended through thursday and will decide on that by this
afternoon`s forecast.

the extended period of offshore flow will continue into
friday...focused over los angeles and ventura counties. little
change expected through wednesday with peak gusts in the 20 to 40
mph range in the wind prone areas. strengthening is possible on
thursday. the humidities will remain incredibly dry with extremely
poor overnight recoveries nearly everywhere.

santa barbara and san luis obispo counties will continue to see
periods of north to east winds (gusts of 15 to 25 mph) through the
week, including areas near the thomas fire. while these winds are
not sundowner winds in terms of strength and source, they will
combine with the continued warm and very dry conditions to result
in elevated to near critical fire weather conditions.

some improvement is expected for friday into saturday as the flow
quickly shifts to more west to northwest, but this shift might
result in gusty winds through southern santa barbara county and the
i-5 corridor. more offshore flow is likely saturday night and
sunday.

if fire ignition occurs, very rapid spread and extreme fire
behavior is likely. those near current wildfires need to stay
aware of and follow official evacuation orders. everyone needs to
exercise extreme caution when handling any potential fire ignition
sources...such as campfires, cigarettes, welding and brush
clearing equipment.

&&

.lox watches/warnings/advisories...
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).
pz...none.

&&

.hazard potential outlook...(thu-mon)
critical fire weather conditions possible thursday and possibly
longer with offshore winds and single digit humidities.

&&

$$

public...mw/rorke
aviation...sweet
marine...sweet
fire...kittell
synopsis...stu

weather.gov/losangeles

NWS LOX Office Area Forecast Discussion



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