Weather Service Report

FXUS66 KLOX 231756 AAA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA 
956 AM PST Fri Feb 23 2018

...updated aviation discussion...

.SYNOPSIS...23/955 AM.

A series of lows will bring possible precipitation into next week.
The precipitation in the mountains will end today, with breezy 
winds into this Friday evening. Then a second low should arrive 
by Monday and persist into Tuesday evening. The third low will
approach by Thursday. The temperatures will be below normal into 
next week except for Sunday, when they may warm to around normal.


.SHORT TERM (TDY-SUN)...23/939 AM.

Cool/breezy day today as another trough passed through the area
early this morning. Still getting some upslope clouds and possibly
a few snow flurries up in the northern mountains and Grapevine
area but those should be ending soon and will let the Winter
Weather Advisory expire at 10am. It will remain breezy however and
we may need a wind advisory for the Grapevine area through early
evening. Otherwise, no significant changes to the forecast through
the weekend. 

***From previous discussion***

It will be clear tonight. Winds should decrease to below advisory
levels in most areas this evening, although may stay gusty in the
mountains. Where the winds drop off tonight, it will become quite
cold. Freeze Watches are in effect for the Central Coast, the 
Interior Valleys of Ventura County, especially for the Ojai 
Valley, and the Santa Monica Mountains. A Hard Freeze Watch has 
been posted for the Santa Ynez Valley. Frost advisories may have 
to be considered for the south coast of SBA County, the VTU County
coast, the coastal valleys of VTU County, and possibly the San 
Fernando and Santa Clarita Valley. Will let the day shift assess
that further, since there is still some question as to whether
on not there may be too much winds tonight.

Dry weather is expected over the weekend. Max temps should be up a
couple of degrees on Saturday, then several more degrees on
Sunday, with temps possibly getting close to normal levels. There
may be another bump up in the north winds late Sat into early
Sunday, mainly from southeastern SBA County through L.A. County.
Where there is no winds, it will be another cold night Sat night,
with freezing temps possible in some coastal and valley areas.

.LONG TERM (MON-THU)...23/442 AM.

A trough will dig southward from the Pacific NW on Mon. Heights 
across the region will fall and onshore flow will increase. This 
should bring a few degrees of cooling to the forecast areas, 
especially west of the mtns. Clouds should increase in the 
afternoon, mainly across northern sections. There is a slight 
chance of showers north of Pt Conception late in the day, but 
overall it should be a dry day.

The models have come into better agreement with this next system,
with the EC backing off its track well out over the water
gathering a fair amount of Pacific moisture, and the GFS slightly
farther west and a bit wetter. Both models show the system 
digging through CA Monday afternoon, with the trough axis right 
along or just off the coast, then show it closing off right across
SBA County Mon night. It then is forecast to move eastward into 
the deserts on Tue. At this point, it appears as though there will
be a chance of showers across the region Mon night into Tue, 
possibly lingering into Tue evening across eastern L.A. County. By
no means does this look like a large rain maker for the region, 
with generally one tenth to one third of an inch of rain expected.
However, if it tracks a bit farther west and gathers some moisture,
totals could be somewhat higher. The EC is stronger and colder 
with the upper low, suggesting rather low snow levels, probably
in the 3500 to 4500 feet range. Still too early for those details
yet, especially with the models changing from run to run.

Dry weather is expected late Tue night through Wed. Beyond Wed,
the models are very different. The EC shows a sharp negatively 
tilted trough approaching the Pac NW Thu, a strong jet sagging 
southward into the forecast area, heights dropping to 550 dm by 
Thu afternoon, and rain spreading into the region. The 06Z GFS 
slower, weaker and farther north with the upper trough, maintains
566-570 dm heights across the region through Thu and keeps it dry.
Have decided to make few changes to the forecast for Thu, keeping
the chance of rain in most areas. However, the trend of the GFS 
is am eye-popping one, and suggests little if any rain across the
region for the end of the week.



At 1730Z, there was no inversion present at KLAX.

Generally hi confidence in the 18Z TAFs. VFR conditions are expected 
at all the airfields through Sat morning. There will be gusty NW to 
N winds at many airfields this afternoon into the evening, with a 20 
percent chance of low level wind shear at times this evening at KSBA 
due to gusty N canyon winds in the vicinity.

KLAX...Generally hi confidence in the 18Z TAF with VFR conditions 
expected through Sat afternoon. There will also be gusty N winds 
this morning to 20 knots switching to NW to W to 26 knots this 
afternoon into the early evening.

KBUR...Generally hi confidence in the 18Z TAF with VFR conditions 
expected through Sat morning. There will also be gusty N winds 
up to 22 knots thru early this evening.


.MARINE...23/836 AM.

For the Outer Waters, good confidence in current forecast. Gale
force winds will continue through this evening with a 70% chance
of Gale force winds continuing Saturday and Saturday night.
Therefore, the GALE WARNING may need to be extended by future
shifts. For Sunday through Tuesday, Small Craft Advisory (SCA)
level winds are likely (80% confidence).

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, there is an 80% chance of SCA level
winds each afternoon/evening today through Tuesday and a 30%
chance of Gale force gusts this afternoon/evening and again Friday
afternoon/evening. For the waters south of Point Conception, SCA
level winds will continue through this evening with a 70% chance
of SCA level winds Friday afternoon/evening. On Monday and
Tuesday, there is a 70% chance of a repeat of SCA level winds in
the afternoon/evening hours.


CA...Wind Advisory in effect until 9 PM PST this evening for zones
      34-35-53-54-59. (See LAXNPWLOX).
     Freeze Watch in effect from late tonight through Saturday
      morning for zones 34-35-44-46. (See LAXNPWLOX).
     Hard Freeze Watch in effect from late tonight through
      Saturday morning for zone 36. (See LAXNPWLOX).
     Wind Advisory in effect until 10 PM PST this evening for
      zones 39-52. (See LAXNPWLOX).
     Winter Weather Advisory in effect until 10 AM PST this
      morning for zones 53-54. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zones 645-650-655. (See LAXMWWLOX).
     Gale Warning in effect until 9 PM PST this evening for zones
      670-673-676. (See LAXMWWLOX).



Low elevation snow possible Monday night into Tuesday creating 
hazardous driving conditions in the mountains, especially across
the Interstate 5 corridor.




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