Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 262100

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
200 PM PDT Thu Apr 26 2018

.SYNOPSIS...26/1134 AM.

A trough of low pressure will gradually move across the West
Coast through Saturday, bringing cooler temperatures and partly
cloudy skies to the area. Additionally, there will be the
potential for gusty west to northwest winds Friday through Monday.
On Tuesday, low pressure will move over the area, resulting in
the potential for some light precipitation for the area.


.SHORT TERM (TDY-SUN)...26/144 PM.

At upper levels, the low currently off the Central CA coast will
move towards the CA coast today then across northern CA Friday and
Saturday. Near the surface, moderate onshore flow will prevail
with an increase in northwesterly flow Friday/Saturday. Expecting only
minor day-to-day temperature changes for the area with afternoon
highs remaining a few degrees below seasonal normals.

The primary forecast concern in the short term will remain winds.
Seeing good onshore gradients today and the accompanying gusty
southwest to west winds across the mountains and deserts. Lake
Palmdale is already gusting to 43 and the advisory will start at
3pm in that area through the evening. Temperatures are a little
below normal, especially near the coasts.

Winds will increase on Friday and Saturday, and widespread
advisory-level west winds across the Antelope Valley are likely.
Additionally with the increasing northerly offshore gradients
(SBA-SMX peaking around -4.3 mb), advisory level northwest to
north Sundowner winds look likely Friday and Saturday for
southern Santa Barbara county.

Of secondary concern, with the upper low moving inland and
dropping our heights the marine layer stratus should deepen and push
further inland across Ventura/LA counties Friday morning and again
Saturday morning. For the Santa Barbara south coast, the increasing
northerly flow should keep area stratus-free Friday and Saturday.
For the Central Coast, stratus should continue tonight and Friday
morning, but will likely be stratus-free Saturday morning due to
northwesterly flow.

Increasing northerly flow could generate some clouds across the
northern mountain slopes and interior Santa Barbara and San Luis
Obispo counties Friday night and Saturday morning.

Sunday will be similar to Saturday.

.LONG TERM (MON-THU)...26/159 PM.

Models in general synoptic agreement through the extended period.
At upper levels, another low spins off of the pattern on Monday
near the California-Oregon border and the trough/low will move
over the area on Tuesday then into Arizona on Wednesday.

Monday looks similar to Sunday. Main concern will continue to be
the potential for advisory-level Sundowner winds across southern
Santa Barbara county. There will likely be fewer coastal clouds on
Monday and skies should remain mostly clear with temperatures a
couple degrees below seasonal normals.

On Tuesday, things become more unsettled as trough/upper low moves
across the area. At this time, the GFS has a closed upper low
just off the Central Coast around noon on Tuesday while the EC has
a broader but deeper trough. Both models continue to show some
light precipitation (0.1-0.25 inches) across the area on Tuesday.
Have placed the greatest (but still not great) chance of showers
over LA County for now, but wouldn`t be surprised to see this
extend over whole CWA in the next couple of days if the GFS
forecast is accurate. The NBM has about 10-15 POP throughout the
CWA and agreed with its greater threat in LA County, so leaned
that way.

On Wednesday, the upper low/trough should have moved far enough
east to keep any precipitation away from our CWA. Clouds will
clear and temperatures will begin to rebound a bit.

By Thursday the 500MB heights will be back to around 580DM where
they are today. Lighter onshore conditions should have it a bit
warmer than today heading into the end of next week



At 1730Z at KLAX, the marine layer was 2000 feet deep. The top of
the inversion was near 4300 feet with a temperature of 17C.

Persistent pattern is expected over the next 24 hours. N of Point
Conception, IFR/MVFR stratus has scoured out across KPRB and much
of the Central Coast. There is a 50% chance that cigs will linger
near KSMX this afternoon. Good confidence for similar timing
IFR/MVFR cigs once again this eve. Less confidence for KPRB which
could be delayed an hour or so from 18Z Taf.

S of Point Conception...Should be a similar timing pattern of
IFR/MVFR stratus developing this eve and scouring out Fri morning
or within an hour of today. There is a 20-30% chance that MVFR
cigs will linger through entire day at coastal airports S of Point
Conception tomorrow.

KLAX...Moderate confidence in the 18Z TAF. There is a 20-30%
chance that cigs could linger from tonight through the afternoon

KBUR...High confidence in the 18Z TAF through 08z then slightly
lower confidence with timing of IFR/MVFR stratus developing
between 09-10z.


.MARINE...26/159 PM.

High confidence that winds will increase to SCA (Small Craft
Advisory) levels across the outer waters this afternoon. Winds
will likely continue at or above SCA levels across the outer
waters thru Mon. There is a 50% chance that winds will increase to
Gale Force across the southern two thirds of the outer waters
zones (PZZ673 and PZZ676) as early as Fri afternoon, with winds
possibly continuing at Gale Force levels at times thru Sun night.

Across the inner waters north of Pt Conception, there is a 20%
chance of SCA level winds this afternoon and evening. There is a
40-50% chance of SCA level winds Fri afternoon and evening, then
SCA level winds are likely Sat afternoon through Mon.

For the inner waters south of Pt Conception...there is a 20%
chance of SCA level winds across western portions of the SBA
Channel this afternoon/evening. SCA winds are likely, especially
across western portions of the zones during the afternoon and
evening hours Fri thru Mon.


CA...Wind Advisory in effect until 10 PM PDT this evening for zone
      59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 PM PDT Monday for zone
      670. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Friday for
      zones 673-676. (See LAXMWWLOX).
     Gale Watch in effect from Friday afternoon through late
      Sunday night for zones 673-676. (See LAXMWWLOX).



There will be potential gale force winds mainly for the outer
coastal waters during the outlook period.



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