Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 210318

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
818 PM PDT Sat Apr 20 2019

.SYNOPSIS...20/813 PM.

Low clouds will cover the coasts and valleys tonight as strong
onshore flow remains. Clouds will begin clearing out Sunday
afternoon as the marine layer retreats and temperatures will warm
up slightly. High pressure begins to build on Monday giving way to
a significant warm up for the first half of the week.


.SHORT TERM (SAT-TUE)...20/817 PM.

Upper level trough moving through the region today combined with
strong onshore flow to bring a significant deepening of the marine
layer to over 4000 feet. A number of stations reported drizzle or
light measurable rainfall this morning, and clouds have lingered
across much of the region this afternoon and evening. The LAX-
Daggett gradient peaked at +10.4 mb onshore this afternoon, which
cranked up the onshore winds in the mountains and Antelope Valley,
with Lake Palmdale reporting the highest wind gust today at 56
mph. A wind advisory remains in effect for the Antelope Valley
through 6 am Sunday. Northwest winds also on the increase this
evening across western portions of the Santa Ynez mountains and
SBA south coast, with local gusts up to 40 mph near Gaviota.

A secondary upper trough will dive into Nevada and interior
portions of California, helping to maintain the strong onshore
flow, deep marine layer, and cool conditions through Sunday. The
marine layer clouds are expected to linger across the coastal
slopes in LA/Ventura counties through Sunday morning, with better
clearing expected in the afternoon. Gusty onshore winds will
continue across the mountains and Antelope Valley on Sunday, but
should remain below advisory levels.

*** From previous discussion ***

An upper level ridge is expected to develop off the CA coast Sun
night and Mon as well. This will bring a strong northerly flow
aloft to srn CA on Mon. For Mon night and Tue, the upper ridge
will gradually build mainly into central CA, with 500 mb heights
over swrn CA increasing to 579-582 dm by late Tue.

An eddy should keep some low clouds along the VTU/L.A. County
coast into some vlys Sun night into Mon morning. Clouds are also
expected along the Central Coast and on the N mtn slopes at that
time. Otherwise, mostly clear skies will prevail across most of
the forecast area Sun night and Mon. Another eddy should help to
develop low clouds along the L.A. County coast Mon night into
early Tue, but for the most part skies will continue to be mostly
clear thru Tue.

Some gusty N winds should affect the SBA County mtns and S coast
tonight but should remain below advisory levels for the most part,
except locally reach advisory levels at times W of Goleta. Gusty sub-
advisory level NW winds will likely affect the L.A./VTU County mtns
tonight especially along the I-5 corridor, with Advisory level winds
expected in the Antelope Vly.

A round of gusty NW to N winds will affect the area Sun night into
Mon morning, with the strongest winds expected in the mtns and
Antelope Vly, as well as the SBA County S coast. Wind advisories
will likely be needed for for many of these areas as we draw closer
to the event.

Gusty NE winds should develop Mon night into Tue morning over the
usual offshore wind-prone areas of VTU/L.A. Counties, but at this
time it appears winds should be just below advisory levels.

Temps should turn a few degrees warmer on Sun but remain a few
degrees below normal, then warm to a few degrees above normal for
many areas on Mon. Temps will really heat up on Tue to well above
normal levels for many areas thanks to the upper ridging and
offshore flow. Highs in the warmest vlys and inland coastal areas
should be in the mid 60s to lower 70s on Sun, mid 70s to low 80s on
Mon, and 80s to around 90 on Tue.

.LONG TERM (WED-SAT)...20/144 PM.

The upper level ridge will build further into srn CA on Wed, then
linger for the most part over the region Thu. The EC keeps upper
level ridging over the area Fri, while the GFS brings in a
relatively weak upper level trof from the E Pac. Weaker upper
level ridging is forecast by the EC on Sat, while the GFS
continues to forecast relatively weak upper level troffiness over
srn CA. For Fri and Sat, both models are dry with decent onshore
gradients, but went with a model blend for the most part.

Skies will be mostly clear across the region Wed. It looks like
varying amounts of night and morning low clouds and fog should
prevail mainly along the coastal plain Thu thru Sat, otherwise
mostly clear skies will continue.

Wed will be the warmest day during the extended period, with highs 5
to 15 deg above normal. A gradual cooling trend should then take
place Thu thru Sat. Highs in the warmest vlys and inland coastal
areas should be in the 80s to around 90 on Wed, upper 70s and 80s on
Thu, mid 70s to low 80s on Fri, and 70s to around 80 on Sat.



At 2330Z, the marine layer was around 3300 feet deep. The top of
the inversion was 4500 feet with a temperature of 12 degrees

Moderate confidence in 00z TAFs with low clouds likely filling
in across most coastal/valley TAF locations tonight into Sunday
morning, generally in the  VFR/MVFR category. Expecting better
burnoff on Sunday afternoon, however still some sct025-035
to linger across many coastal/valley airfields.

KLAX...Overall, moderate confidence in 00z TAF. Low clouds
with VFR conditions generally expected to lower to MVFR category
tonight into Sunday morning. Expecting better burnoff on Sunday
afternoon, however still a 20 percent chance of cigs lingering.

KBUR...Overall, moderate confidence in 00z TAF. Low clouds
with VFR/MVFR conditions generally expected at KBUR tonight into
Sunday morning. Expecting better burnoff on Sunday afternoon,
however still a 20 percent chance of cigs lingering.


.MARINE...20/151 PM.

For the Outer Waters, low to moderate confidence in the current
forecast. Winds and seas are expected to rise to a minimal Gale
Warning in the outer waters through tonight, at best. There is a
30 percent chance of only SCA level winds tonight. The southern
zone (PZZ676) will be (SCA) this afternoon through early this
evening. This evening, there is a 50% chance for Gale force winds
to develop through late tonight or pre-dawn hours Sunday. Gale
Warnings will remain in place. There is a 50% chance for more
Gale force winds for the outer waters Sunday afternoon and evening

For the Inner Waters north of Point Sal, low confidence in
current forecast. Winds and seas will rise to (SCA) levels this
afternoon through early this evening. However, the latest model
run has lowered wind speeds for most locations, enough to bring a
Gale Warning for this zone into question. Therefore, a Small Craft
Advisory through late tonight has replaced the Gale Warning for
this zone. There is a good chance that a (SCA) will be needed for
Sunday afternoon into the overnight hours.

For the Inner Waters south of Point Conception, moderate
confidence in current forecast. Winds and seas will rise to
(SCA) for the western portion of the Inner Santa Barbara Channel
this afternoon and continue into Sunday morning. Elsewhere, there
will be some local NW winds to 20 kt around the NW portion of
(PZZ655) or around Anacapa Island this afternoon and evening
hours. From Sunday afternoon through Wednesday, winds and seas are
expected to remain below SCA levels.


CA...Wind Advisory in effect until 6 AM PDT Sunday for zone 59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
      zones 645-650. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Sunday for zones
      670-673-676. (See LAXMWWLOX).



No significant hazards expected.



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