Scientific Forecaster Discussion
fxus66 klox 200303
Area forecast discussion
National Weather Service Los Angeles/Oxnard California
803 PM PDT Sat Oct 19 2019
Gusty northerly winds will continue over much of the area,
through Sunday, with strong winds over the Santa Barbara South
Coast and Santa Ynez range, and the Interstate 5 corridor. By
Sunday night, the winds will shift to the northeast, bringing
weak Santa Ana winds to portions of Los Angeles County and the
Ventura mountains. Above normal temperatures are expected Monday
Short term (sat-tue)...19/802 PM.
Except for some patchy low clouds across portions of the central
coast and just off the central coast this evening, skies were
clear across the region. Once again tonight, expect any clouds to
dissipate or be forced offshore as low level gradients turns
northeasterly on the central coast after midnight.
North-S pressure gradients between ksba/smx, sba/kbfl and klax/kbfl
were all more strongly offshore this evening than at this time on
Fri evening, and this will continue overnight. In addition,
subsidence and northerly winds aloft will increase overnight
being a vort lobe moving through the region this evening. And,
there will be some cold air advection as well. Gusty winds were
already occurring in the mtns of l.A., Vtu, and sba County, across
the adjacent South Coast of sba County, and in locally in the
valleys of l.A. And eastern vtu counties, and winds are expected
to increase and become more widespread overnight.
Winds will eventually push into the Santa Monica range and into
coastal sections of l.A. County from Malibu to Hollywood and
throughout the Westside. This could be a rather widespread wind
event for coastal sections of l.A. County tonight and Sun morning,
not just confined to locations immediately below passes and canyons
from Malibu to the Hollywood Hills.
Winds have diminished on the central coast, so the advisories
there have been allowed to expire. Otherwise, current wind
advisories and high wind warnings look good and will remain
Wind gusts to 60 mph are expected, and isolated gusts to 70 to 75
mph are likely near Montecito hills and in the peaks above the
Interstate 5 corridor. Winds will increase to advisory levels in
the eastern valleys of vtu County, the San Fernando Valley, the
Santa Monica Mountains and in coastal sections of l.A, County
***From previous discussion***
The gusty winds will begin to diminish across the mountains and
South Coast of sba County and in coastal sections of l.A. County
by noon Sunday, but should linger at advisory or warning levels in
l.A. And Ventura County mtns and valleys into the mid afternoon
hours. Max temps on Sunday will likely Jump Up several degrees.
For Sunday night and Monday, low level flow will turn more
northeasterly. This should shift the focus of the winds mainly to
Los Angeles and Ventura counties. Upper support will be weaker,
but gradients may be sufficient to produce some marginal advisory
level northeast winds late Sun night and Mon morning. Max temps
will jump several more degrees on Mon, especially west of the
mountains, with highs reaching or exceeding 90 degrees in some
coastal and valley areas.
Heights will continue to rise on Tue to around 592 dm as a strong
upper high noses into the region from the eastern Pacific.
Gradients will remain offshore, possible even enough for some
locally gusty winds across portions of l.A. And vtu counties, but
nothing at advisory levels expected. Tuesday should be the warmest
day for coastal and valleys, with highs in some of the warmer
locations possibly getting close to 95 degrees. No heat products
are planned to be issued at this time.
Long term (wed-sat)...19/213 PM.
The upper high trying to move in from the eastern Pacific will be
forced westward Wed and Thu as the trof drops southward out of
Canada and into The Rockies and Great Basin. Gradients will turn
weakly onshore Wednesday. This should bring some several degrees
of cooling, especially to coastal and valley areas.
Ensemble models that were previously suggesting another offshore
event on Friday/Saturday have advanced the event to Thursday
putting the odds of greater than 34 kt winds at better than 80
percent in the usual Santa Ana locations. There should also be
significant warming, and very dry conditions are expected once
The Thu/Fri event should be over by Saturday and cooler, calmer
conditions will return. Ensemble members hinting at a chance of
precipitation for la by Monday the 28th...but that's way out
there in the forecast and i'm probably wishcasting.
At 1730z, there was no marine layer at klax.
High confidence in VFR conditions at all terminals thru the
period. There is a chance of periods of moderate to strong
turbulence at terminals south of Point Conception.
Strong and gusty west winds can be expected at kpmd and kwjf this
afternoon and tonight. For kwjf, there is a 50% chance of MVFR
vsbys and a 10%-20% chance of LIFR vsbys due to blowing dust and
sand for late this afternoon into early evening as expected wind
gusts reach around 40 kt.
Klax...hi confidence in VFR conditions thru Sun afternoon. There
is a 50%-60% chance of north cross winds up to 25 kt 06z-10z with
lighter cross winds up to 15 kt 10z-14z. The timing of the cross
winds may be off +/- an hour or two, and there is a small chance
the cross winds could be even stronger at times.
Kbur...hi confidence in VFR conditions thru Sun morning. Gusty
north winds are expected from about 03z-12z, with a 40% chance
winds could gust over 20 kt at times.
For the outer waters...generally hi confidence in the current
forecast. Gale force winds will affect the southern zone (pzz676)
through this evening. Otherwise, Small Craft Advisory (sca) winds
and seas will affect the waters through Sunday night. There is a
50% chance of Small Craft Advisory gusts for pzz673 Monday afternoon, otherwise
winds and seas are expected to remain below Small Craft Advisory levels Monday
For the inner waters north of Point Conception...moderate to hi
confidence in the current forecast. Small Craft Advisory level wind gusts can be
expected through this evening, and there is a 50% chance of Small Craft Advisory
wind gusts at times Sunday and again on Tuesday. Otherwise, winds
and seas are forecast to be mostly below Small Craft Advisory levels through
For the inner waters south of Point Conception, moderate
confidence in the current forecast. Small Craft Advisory wind
gusts can be expected this evening and again Sunday evening for
the western Santa Barbara Channel. There is also a 60%-70% chance
of Small Craft Advisory level north wind gusts from Point Mugu to Santa Monica out
to sana Monica Bay from this evening thru Sun morning and again
Sunday evening. Otherwise, winds and seas should remain below Small Craft Advisory
levels through Thursday.
The combination of a large swell and gusty winds over the coastal
waters will keep high surf along the central coast longer than
expected. Surf of 8 to 11 feet will continue on exposed west and
northwest facing beaches now through early Sunday evening before
subsiding Sunday night.
Fire weather...19/343 PM.
Gusty northerly winds will be widespread across the region through Sunday
evening, with the strongest burst of winds tonight through Sunday morning
when the tightest north-south offshore pressure gradients coincide with peak
upper level wind support. The strongest winds tonight through Sunday morning
are expected to be across the Santa Ynez Mountains and adjacent foothills of
the Santa Barbara South Coast, as well as the Interstate 5 corridor across
the mountains and Santa Clarita valley, as well as the Santa Monica Mountains
and San Fernando Valley, where wind gusts of 40 to 60 mph will be common.
Isolated gusts up to 75 mph will be likely across portions of the Interstate
5 corridor and near Montecito hills. During this time, damaging winds are
likely, resulting in the threat of downed trees and power lines. Other areas
prone to northerly winds will generally have wind gusts in the 30 to 50 mph
range through Sunday evening, including the Los Angeles coast(from Malibu to
Hollywood and the westside), the Ventura valleys (near Highway 33 corridor
and eastern portions), and the central coast. The lax-Bakersfield and Santa
Barbara-Bakersfield gradients peaked at -5.7 mb and -5.9 mb respectively
this morning, and are expected to peak between -6.0 and -6.5 mb by early
Sunday morning. Local studies indicate these north-south pressure gradients
that we are expecting are very rare for October (exceeding 97th percentile),
indicating this is a rare strong northerly wind event for October.
Minimum humidities will generally range between 8 and 20 percent today through
Sunday. Recoveries at night will be moderate across the north facing mountains
near the Kern County line, with poor recoveries in the foothills, as well as
downslope mountain and valley areas. With humidities trending drier than earlier
expected, the red flag warnings were expanded to include the mountains of Los
Angeles and Ventura counties (including the Santa monicas), as well as the
San Fernando and Santa Clarita valleys. The strong northerly winds will have
the potential to bring very rapid fire spread, extreme fire behavior, and long
range spotting with any new fire ignitions.
The winds are expected to shift to northeasterly Sunday night into Monday
when gusts between 25 and 40 mph will occur across wind prone areas of Los
Angeles and Ventura counties (strongest in the Los Angeles County mountains), as
well as the central coast. Offshore winds are expected to be slightly weaker
Tuesday morning. Elevated to brief critical fire weather conditions will continue
across these areas through Tuesday. Minimum humidities will generally range between
10 and 20 percent on Monday and Tuesday, while high temperatures climb to between
85 and 95 degrees. Another warm and potentially very dry Santa Ana wind event
will bring the potential for critical fire weather conditions Thursday into Friday.
California...high surf advisory in effect until 8 PM PDT Sunday for zones
34-35. (See laxcfwlox).
Wind Advisory in effect until noon PDT Sunday for zones
39-41. (See laxnpwlox).
Wind Advisory in effect until 3 PM PDT Sunday for zones
44>46-547. (See laxnpwlox).
High Wind Warning in effect until noon PDT Sunday for zone
52. (See laxnpwlox).
High Wind Warning in effect until 3 PM PDT Sunday for zones
53-54-88. (See laxnpwlox).
Wind Advisory in effect until 3 am PDT Sunday for zone 59. (See laxnpwlox).
Red flag warning in effect until 10 PM PDT Sunday for zones
239-246-252>254-288-547. (See laxrfwlox).
Pz...Small Craft Advisory in effect until 9 PM PDT this evening
for zone 645. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Sunday for zone
650. (See laxmwwlox).
Small Craft Advisory in effect until 9 am PDT Sunday for zone
655. (See laxmwwlox).
Small Craft Advisory in effect until 3 am PDT Monday for
zones 670-673. (See laxmwwlox).
Gale Warning in effect until 9 PM PDT this evening for zone
676. (See laxmwwlox).
Hazard potential outlook (tue-sat).
Elevated to critical fire weather conditions possible over Los
Angeles and Ventura counties Thursday/Friday due to hot and dry
conditions and locally breezy Santa Ana winds.