NWS Los Angeles, CA wrote its last area forecast discussion before the first event at Nov 26, 6:01 AM PST, 3 hours 19 minutes earlier.
Area forecast discussion, Nov 26, 6:01 AM PST, 3 hours 19 minutes before
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
601 AM PST Thu Nov 26 2020
.SYNOPSIS...26/411 AM.
There will be patchy morning low clouds and fog along the coast
and in coastal adjacent valleys south of Point Conception. Gusty
Santa Ana winds will develop today, peaking late tonight into
Friday morning but continuing through at least Saturday. Afternoon
temperatures will warm into the weekend.
&&
.SHORT TERM (TDY-SAT)...26/600 AM.
It is the battle of the low clouds and the northerly winds across
Los Angeles County early this morning. Strong winds have already
developed in the mtns of L.A. and VTU Counties, and have even
spread into the Santa Clarita Valley, the northern San Fernando
Valley, and the eastern Valleys of Ventura County. At the same
time. low clouds were widespread in coastal sections of L.A.
County and the San Gabriel Valley, and were daring to make an
advance in the southern and eastern San Fernando Valley.
With N-S gradients continuing to increase, it is difficult to see
this battle ending well for the clouds this morning, and expect
their northern and westward advancement will soon be halted.
Furthermore, a rather strong vort lobe was currently swinging
southward through central CA. This will sweep across the region by
mid morning, with increasingly strong northerly flow aloft and a
deep layer of rather strong subsidence behind it. This should
cause the winds to further increase in the mtns, and advisory
level winds will become widespread in most valleys of L.A./VTU
Counties, likely vanquishing any low clouds by mid or late
morning.
Gusty advisory level NE winds will also likely spread into the
Ventura County Coastal Plain and N to NE winds to coastal
sections of L.A. County below passes and canyons from Malibu to
the Hollywood Hills by late morning, or by early afternoon if the
clouds hang tough. Today will be a cool day across the region. After
any clouds this morning, clear skies are expected through Sat.
N to NE winds through the atmosphere are expected to increase
across the region later today, so expect winds to get stronger
through the day. The sharpening upper trough will evolve into a
closed low over southern Nevada this evening, then it will move
into Arizona Fri morning. It looks as though the peak of this
wind event will be tonight and Fri morning, when upper support
across the region is as its greatest. Pressure gradients peak
between 5 and 7 mb offshore depending upon the model, but with
this event, it is the upper support that should help kick winds
into at least the low end High Wind Warning category in many of
these areas. Rather high confidence that locations the mtns of
L.A./VTU Counties, the Santa Monica Mountains and the Santa
Clarita Valley will have High Wind Warning level wind gusts, so
warnings there were issued with good confidence. In fact wind
gusts to 75 mph are possible in some of the windier mountain
locations.
While there will likely be warning gusts in the valleys of VTU
County and the San Fernando Valley, they will probably be
confined to a few of the windier locations not near major
population centers. However, places such as Porter Ranch may well
have gusts to 60 mph, so felt it was worth including the valleys
in the High Wind Warning, especially since it is a major holiday,
and since many people may be trying to celebrate outdoors this
year. Have also added a wind advisory for the San Gabriel Valley
from late this afternoon through late tonight, with the strongest
winds expected in the foothills. Gusty NE winds will also affect
Catalina Island and the vulnerable NE facing harbors such as
Avalon Harbor and Two Harbors
Winds are expected to gradually diminish Friday afternoon, but
still may remain near advisory levels in some areas. Max temps
should be up several degrees on Fri, especially west of the mtns.
Offshore flow will continue Friday night and Saturday, and while
winds should mostly be below advisory levels, there may be a few
locations that need advisories. Max temps should be up a few
degrees on Sat as heights rise.
Where is is not breezy, it will be very chilly as night due to
clear skies and very low humidities, with some local freezing
temps possible on the Central Coast, the south coast of SBA
County, in the Santa Ynez Valley, and wind sheltered areas of VTU
County tonight through Sat night.
.LONG TERM (SUN-WED)...26/551 AM.
Weak offshore flow will continue across the region through Monday.
Now the models each show a different, but very non-descript upper
pattern for Sun and Mon, but basically keep the heights about the
same. Therefore, do not expect much change in max temps which
will generally near to slightly above normal, at least west of the
mtns. Both models show a ridge developing off the coast on Tue,
which should lead to some warming. Increasing N-S gradient should
bring some gusty N winds to those areas prone to northerly winds.
From Tue afternoon through Wed, both the EC and GFS show an upper
low diving southward from the northern Rockies into Arizona in
the case of the EC, or Utah as in the case of the GFS. This causes
a sharp increase in offshore gradients by Wed, so there could be
another round of very gusty Santa Ana winds. In fact, by Thu, the
GFS shows a gradient of -8.2 mb between KLAX and KDAG. Needless
to say, no rain in sight.
&&
.AVIATION...26/1204Z.
At 0815z at KLAX... There was no inversion.
Overall... Moderate to high confidence in the current TAFs. LIFR/IFR
conditions will remain at KLAX and KLGB through 17z and there is a
thirty percent chance of similar conditions developing at KOXR,
KCMA, KSMO, KVNY, and/or KBUR through 17z. Otherwise and
elsewhere, VFR conditions will prevail.
KLAX... Moderate confidence in the current TAF. LIFR/IFR
conditions will likely remain at KLAX through 16z, otherwise VFR
conditions will prevail through the forecast period. There will
not be any east winds greater than 8 kts.
KBUR... High confidence in the current TAF. There is a thirty
percent chance of LIFR/IFR conditions developing through 17z.
Otherwise, VFR conditions will prevail throughout the forecast
period.
&&
.MARINE...26/333 AM.
Across the outer waters... Conditions will be Small Craft
Advisory (SCA) level today,then will be elevated but diminish to
below SCA level through Monday.
Across the nearshore waters of the Central Coast... There is a
forty percent chance of SCA level winds tonight. Otherwise, winds
will be elevated but will remain below SCA level through Monday.
Across the inner waters south of Point Conception... Winds off the
Ventura and Los Angeles County coastline will increase to at
least SCA level and possibly gale force level this afternoon
through Friday night. This will affect Catalina Island, including
Avalon Harbor. Otherwise and elsewhere, conditions will be
elevated and gusty but below SCA level.
Patchy morning coastal fog, locally dense, will continue through
mid morning primarily south of Point Conception.
&&
.BEACHES...26/336 AM.
A long-period northwest swell will bring high surf to beaches
along the Central Coast today. The surf will peak this morning at
12 to 15 feet with local sets to 18 feet along west to northwest
facing beaches. Strong rip currents are likely and beach erosion
is possible. Minor coastal flooding around the time of high tide
will be possible.
Most of the swell energy will avoid the southern California
bight. Beaches south of Point Conception will have elevated surf
and a high risk of rip currents today, but a high surf advisory is
not needed for this area.
&&
.FIRE WEATHER...26/559 AM.
Red Flag Warnings now in effect for most of L.A. County and all
of Ventura County, from 2pm Today through 6pm Friday evening.
Moderate to locally strong Santa Ana winds will develop through
the day on today, peak this evening through Friday morning, then
gradually weaken into Saturday but stay locally breezy through the
weekend. Wind gusts between 40 and 65 mph are expected over much
of Los Angeles and Ventura Counties during the peak. Meanwhile,
humidities will lower sharply this afternoon and evening to 12 to
25 percent, lowering further to 5 to 15 percent for Friday
through Sunday. As a result, Red Flag conditions are expected to
form over much of Los Angeles and Ventura Counties by this
afternoon or evening when the wind and drier air start to
coincide, then continue through Friday afternoon. There is a 50
percent chance for low-end Red Flag criteria to be met Friday
night through Saturday or Sunday over the mountains and windiest
valleys, including the Santa Clarita and Ventura Valleys. There is
a growing potential for moderate Santa Ana winds and Red Flag
conditions over Los Angeles and Ventura Counties sometime Tuesday
through Thursday.
We are urging the public to be extremely cautious with anything
that can start a fire. Some ignition sources are obvious
(campfires, welding equipment, cigarettes, fireworks) but others
are less so (lawn trimmers, dragging trailer chains, firearms).
Those living in wildland interfaces and areas vulnerable to
wildfire should have a plan and be ready to evacuate if a fire
starts. Any wildfire that starts has the potential to spread
rapidly and exhibit extreme fire behavior due to the combination
of very dry fuels, low humidity, and strong gusty winds.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 3 AM PST Friday for zones
34-35. (See LAXCFWLOX).
Wind Advisory in effect from 10 AM this morning to 3 PM PST
Friday for zones 40-41. (See LAXNPWLOX).
Wind Advisory in effect until 7 PM PST this evening for zones
44>46-88-547. (See LAXNPWLOX).
High Wind Warning in effect from 7 PM this evening to 3 PM
PST Friday for zones 44>46-88-547. (See LAXNPWLOX).
Wind Advisory in effect until 4 PM PST this afternoon for
zones 53-54. (See LAXNPWLOX).
High Wind Warning in effect from 4 PM this afternoon to 3 PM
PST Friday for zones 53-54. (See LAXNPWLOX).
Red Flag Warning in effect from 2 PM this afternoon to 6 PM
PST Friday for zones 240-241-244>246-253-254-288-547-548. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 1 PM this afternoon to 6
PM PST this evening for zone 655. (See LAXMWWLOX).
Gale Watch in effect from 6 PM PST this evening through late
tonight for zone 655. (See LAXMWWLOX).
Small Craft Advisory in effect until midnight PST tonight for
zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PST Friday for zone
676. (See LAXMWWLOX).
&&
.HAZARD POTENTIAL OUTLOOK (SAT-WED).
An extended dry and warmer pattern is expected Saturday through
Monday with persistent elevated fire weather conditions. Another
strong Santa Ana wind event is possible next Tuesday and
Wednesday.
&&
PUBLIC...DB
AVIATION...Kj
MARINE...Kj
BEACHES...Kj
FIRE...Kittell/Smith
SYNOPSIS...Kj
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