Area Forecast Discussion
Issued by NWS Los Angeles, CA

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688
FXUS66 KLOX 270027
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
527 PM PDT Wed Apr 26 2017

.SYNOPSIS...
There may be possible precipitation in the Ventura mountains
early Thursday. A high to the west...and a low to our east will
bring fair skies...gusty winds and above normal temperatures into
Sunday. The high will move in by Monday for fair skies... with an
onshore flow to start a cooling trend at the coast.

&&

.SHORT TERM...(TDY-SAT)

Latest satellite imagery showed mid to high level clouds
approaching the Central Coast ahead of a shortwave trough moving
southeast through Central California. Patchy marine stratus
is hanging on off the Central Coastal. Otherwise sunny skies
except for partly to mostly cloudy skies developing with mountain
wave activity, most prominent to the lee of the Tehachapi Mtns
across the Los Angeles Mountains into the Antelope Valley.
Temperatures so far today are matching up well with forecasted
highs to the west of the mountains. However, some areas north of
Point Conception and across the interior will likely fall several
degrees short of forecasted highs due to increasing cloud
coverage.

A shortwave trough will pass to the east of the forecast area
this evening, bringing increasing cloudiness to interior areas
with a slight chance of upslope showers for north facing slopes.
It will also reinforce northerly winds to Southwest California
beginning this evening. Strong upper level support with feature
has prompted the issuance of a high wind warning across the Los
Angeles and Ventura County Mountains, for this afternoon through
Friday morning. However, there may be a brief lull in warning
level winds across the area sometime Thursday afternoon. Advisory
level northwest to north winds will become more widespread this
evening with the San Gabriel Valley being the latest addition to
wind advisories. A second shortwave trough is expected to pass to
the east again Thursday evening, supporting continued unseasonably
gusty northerly winds to many of the same areas experiencing the
gusty winds this evening through Thursday morning. Winds will
probably remain just below advisory levels for coastal areas of
the Central Coast Thursday afternoon and evening.

Friday into Saturday a long wave trough deepens across the Four
Corners Region as it gradually shifts east. Surface high pressure
building in behind the strengthening trough will support a
transition to more northerly winds Friday and offshore by
Saturday. Winds are expected to weaken during this time but will
still likely be advisory levels for wind prone areas. As a result,
current wind advisories across the mountains and some valley
areas will likely need to either be extended through early
Saturday or reissued.

Interior areas will see little change in temperatures through
Friday with some warming possible Saturday as a Ridge aloft
nudges closer to California with mostly sunny skies. Areas west
of the mountains, especially south of Santa Barbara will
considerable warming and drying through Saturday due to the
downsloping winds off the mountains. High temperatures projected
to be around 10 degrees warmer then todays highs with low to mid
90s possible across the warmest valleys. It will be among the
warmest temperatures so far this year with low end heat impacts
possible, especially for at risk populations such as the young,
elderly, and unprepared.

.LONG TERM...(SUN-WED)

Good confidence in the forecast through Monday with moderate
confidence Tuesday and Wednesday. Weakly offshore or near neutral
surface pressure gradients Sunday morning are expected to shift
moderately onshore by the afternoon providing notable relief from
the heat for coastal areas. However, downsloping winds combined
with a ridge of high pressure aloft will provide some warming
across interior areas. Onshore flow will likely continue into
Monday with continued cooling across coastal areas into the
valleys and little change across interior areas. Low clouds and
patchy fog are possible as early as Monday morning, but more
likely overnight Monday into Tuesday morning. Model guidance is
hinting an offshore push providing near neutral to offshore
surface gradients by Wednesday. This may hamper cooling currently
advertised as well as limit marine layer influence to the west of
the mountains.

&&

.AVIATION...

27/0000Z

At 2325Z at KLAX, there was a 600 foot marine layer. The top of
the inversion was near 1800 feet with a temperature of 23 degrees
C.

Very good confidence in VFR cig/vis fcst for all TAFs south of Pt
Conception. Fair confidence in winds forecast. KVNY might have
stronger winds and KBUR might be weaker than fcst. KSBA winds may
vary in direction between 220 and 350. KLAX and KSMO may have
stronger northerly winds than fcst.

North of Point Conception there is good confidence that marine
layer stratus will develop but there is a 40 percent chc of LIFR
cigs and vis after 08Z through 16Z.

KLAX...Very good confidence in VFR cig/vis fcst. There is a 30%
chance of Northerly cross winds over 22 kt from 02Z to 11Z.

BUR...Very good confidence in VFR cig/vis fcst. There is a 40
percent chc that the winds from 11Z to 17Z will be 12G22KT.

&&

.MARINE...26/200 PM

For the Outer Waters, high confidence gale force winds through
Friday night, with SCA conditions, at least,likely through
the weekend.

For the Inner Waters, moderate to high confidence in SCA conds
through Fri night. There will likely be some gale force gusts,
especially across western sections. There is a 20-30% chance that
Gale Warning may be needed, especially late Thu through Fri
evening.

Due to strong winds throughout the waters, seas will be very
choppy in all areas this week, making for hazardous boating
conditions through the week.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PDT this evening for zones
      34-35. (See LAXNPWLOX).
     Wind Advisory in effect until 9 AM PDT Friday for zones
      39-46-52-59-547. (See LAXNPWLOX).
     Beach Hazards Statement in effect through Friday evening for
      zones 40-41. (See LAXCFWLOX).
     Wind Advisory in effect until 9 AM PDT Thursday for zone 41. (See LAXNPWLOX).
     High Wind Warning in effect until 9 AM PDT Friday for zones
      53-54. (See LAXNPWLOX).
     Wind Advisory in effect until 3 PM PDT Friday for zone 88. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 645-650-655. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Saturday for zones
      670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
Gusty northeast winds are possible across portions of Los Angeles
and Ventura Counties Saturday, with well above normal
temperatures expected.

&&

$$

PUBLIC...Munroe
AVIATION...Rorke
MARINE...Sweet
SYNOPSIS...STu

weather.gov/losangeles



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