National Weather Service Raw Text Product

Bulk Download

Start UTC Date @0z:
End UTC Date @0z:

FXUS66 KLOX 111146

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA 
346 AM PST Mon Dec 11 2017

Updated Aviation Discussion

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



A rex block in some form or another will sit atop of the state for
the next three days. Hgts will sit around 580 DM which is about 10
DM higher than normal. High pressure in the great basin will keep
the offshore flow going through the period. There will be a slight
bump up in the northerly component of the pressure grads on Tue
and these will persist into Wednesday.

There will be very little in the way of day to day changes. There
will be northeast to east morning winds in the usual locations but
these winds will all be below advisory levels. Max temps will be 8
to 12 degrees above normal across the coasts and vlys and 4 to 8
degrees above normal across the interior. All bets are off for
temps across the Central Coast where the smoke could wreak havoc 
with the temps (Yesterday SLO airport with smoke was 6 degrees 
cooler than the city of SLO and Santa Ynez was 11 degrees cooler 
than the day before due to a thick layer of sun blocking smoke) 

SBA county will struggle with smoke and if the offshore winds
relax enough in the afternoon/evening then VTA county will also
have smoke issues.

The lower wind speeds will be a boon to the fire fighting efforts
but the very low humidities will continue and these will for sure
hinder the efforts to control the fires. The increase in the north
component of the winds will have to be closely monitored for
potential fire impacts as well.


Not much change at all on Thursday. The upper pattern is no longer
a rex but rather just a big state covering upper ridge extending
from the southwest. Sfc grads relax some so there may not even be 
much in the way of morning breezes. Temps will not change much.

All mdls now agree that a weak inside slider will zip down the
CA/NC border on Friday. Hgts will fall and more importantly the
relentlessly offshore flow will turn onshore in the afternoon.
There will be cooling esp at the coast but max temps will remain
above normal.

If the gradients go according to forecast the continuous offshore
streak will end Friday afternoon and there will have been 13
consecutive days of offshore flow. There have only been 17 longer
streaks since 1948. This streak while impressive does not come
close to the record set in Dec 53 to Jan 54 of 24 days.

The passing of the inside slider will usher in yet more offshore
flow on Saturday with more of a northerly push followed Sunday by
a Northeast Santa Ana push. At this time the offshore flow for the
weekend does not look too particularly strong. Max temps will 
bump up a few more degrees as well.



At 0930Z at KLAX, there was a sfc based inversion to 700 feet with
a temperature of 24 C.

Good confidence in TAFs except for KSMX, KSBA, KOXR and KCMA where
periods of MVFR cigs and MVFR/IFR vis are possible at times.

KLAX...Very good confidence in TAF. Any east winds should remain 
less than 7 knots.

KBUR...Very good confidence in TAF.


.MARINE...11/310 AM.

For the Inner Waters south of Point Conception, below SCA 
offshore winds are possible each morning through Wednesday.

The nearshore 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...10/100 PM.

Another critical fire weather day for many areas along with heavy
smoke impacts west of the Thomas Fire. Red Flag Warnings were
extended for Los Angeles and Ventura Counties through Monday 8 PM
and Santa Barbara County Mountains until 6pm today. Large plume
development and very low humidity was the main reasoning for 
extending the warning in SBA Co. today. 

Wind gusts up to 45 mph have occurred today in the windier canyons
and passes of Los Angeles and Ventura Counties with widespread
humidities between 3-12 percent. Expect winds to slowly decrease
tonight, but remain locally gusty when diurnal Santa Ana's uptick
toward Monday morning. Speeds should be less strong on Monday 
(gusts 30-40 mph) with LAX-DAG pressure gradients near -6mb or
about 1mb weaker than today. Unfortunately there will be a repeat
of poor overnight humidity ranging from 10-25 percent and many 
areas returning to less than 10 percent during the day on Monday. 
Temperatures will remain well above normal on Monday which could 
lead to additional large plume growth over existing fires in a 
deep mixing layer. There is a possibility of an extended red flag
in Santa Barbara County on Monday. 

Low daytime humidity and poor overnight recoveries are likely to
persist across the entire fire district through Thursday. Santa 
Ana wind speeds are predicted to be weaker Monday night into 
Tuesday, but there could be local gusts in valleys and mountains 
close to red flag warning criteria. Still too early to say red 
flags will not be needed then. Long range forecasts show a slight 
increase in onshore flow and humidities arriving (hopefully) on 
Friday and Saturday. No rain possibilities expected over the next 
10 days though. 

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.


CA...Red Flag Warning in effect until 8 PM PST this evening for
      zones 240-241-244>246-253-254-288-547-548. (See LAXRFWLOX).


Critical fire weather conditions and locally gusty offshore winds
could continue into early next week.