Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 190902

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
202 AM PDT Thu Apr 19 2018

.SYNOPSIS...19/1256 AM.

A weakening cold front will bring some showers and mountain snow
showers with gusty winds and cooler temperatures to the area
today. High pressure will then build in for dry and warmer
conditions Friday, with above normal temperatures expected away
from the coast over the weekend into early next week. Night to
morning coastal low clouds and fog are likely this weekend.


.SHORT TERM (TDY-SAT)...19/201 AM.

Doppler Radar indicated cold front band of moderate to locally
heavy rain was pushing into the Central Coast around 2 am this
morning. Satellite imagery continues to show the associated upper
level low pressure system diving south off the Central Coast. A
100+ knot jet streak is visible due to enhanced high cloud cover
about 180 miles southwest of Point Conception. Down sloping off of
the Transverse Ranges of SBA and VTA counties combined with the
upper level support outrunning the surface cold front is expected
to lead to rapid weakening of the main rain band early this
morning with only isolated to scattered showers continuing into
VTA and LA counties later this morning. Wrap around moisture may
support showers lingering into the afternoon across the north
slopes of LA and VTA county. This is an unusually cold system for
late April with snow levels falling down to around 4000 feet at
this morning before likely rising some with assistance of the
spring sun angle by the afternoon. An isolated thunderstorm or two
can`t be ruled out with this cold and dynamic system, even though
available moisture is somewhat lacking. This threat is slightly
higher with the rain band early this morning, transition to
interior mountains by this afternoon. Rain and snowfall amounts
are expected to be generally light, except with the more organized
rain band pushing into the Central Coast. There rainfall amounts
will generally be less than one third of an inch, however local
one half inch plus amounts are possible in areas affected by
heavier showers. Snowfall up to around an inch is possible, mainly
about 4000 feet in SBA county into northern slopes of VTA and LA
county. Fairly widespread onshore to northwest winds are expected
with this system later this afternoon into this evening,
transitioning more northerly tonight (see our NPWLOX product for
the latest details).

A ridge of high pressure is expected to build in rapidly behind
this system with H5 heights climbing dramatically from around 560
dm this afternoon to 580 dm by Friday afternoon. Supporting a
transition from widespread highs in the 60s today to highs in the
70s Friday. It looks like a fairly typical May pattern Saturday a
strong thermal or temperature gradient from the coast to inland
with highs in the 60s to around 70 at the coast to well into the
80s warmer coastal valleys into the interior. Breezy winds are
likely for wind prone interior areas and southwest SBA county by
Saturday evening. A moderate eddy will likely help to spin up low
clouds and patchy fog for typical areas of LA and possibly VTA
county by Saturday morning.

.LONG TERM (SUN-WED)...19/125 AM.

Above average confidence in the forecast through Monday with below
average confidence for the remainder of the extended period.

Flat ridging aloft will likely continue through Monday and may
last through Wednesday or so. Model guidance is in agreement that
at least weak troughing aloft will develop sometime later next

With this setup above average temperatures will likely continue
away from the coast with low clouds and closer to normal
temperatures more likely closer to the coast through Tuesday or
Wednesday. Breezy onshore winds are likely by the late afternoon
or early evening each day for far interior areas. Cooler
conditions are the best bet for interior areas for the middle of
next week with the potential for increasing clouds.



At 2232Z at KLAX, the marine layer was 800 feet deep. The top of
the inversion was at 1400 feet with a temperature of 14C.

Good confidence in TAFs through 09Z. Lower confidence after 09Z
with a 30 percent chc of MVFR cigs 09Z-17Z. There is a 10 percent
chc of a thunderstorm over KPRB, KSBP and KSMX 11Z-15Z.

KLAX...High confidence in VFR conds through 09Z. There is a 30
percent chc of BKN025 09Z-16Z. There is a 10 percent chc -SHRA
15Z-19Z. Good confidence in wind forecast.

KBUR...Good confidence in TAF. There is a 20% chance of MVFR cigs
after 12Z-16Z. There is a 10 percent chc -SHRA 15Z-19Z.


.MARINE...18/708 PM.

Generally high confidence in Small Craft Advisory (SCA) level
winds developing across all coastal waters tonight. SCA winds and
seas are then expected through late Thu night, although may drop
below SCA levels in some areas late tonight/Thu morning.

Steep short-period seas are expected later today through at least
Thu night.

SCA winds are expected across the outer waters Fri afternoon or
evening through Sat evening, and possibly into Sunday.


CA...Wind Advisory in effect from 1 PM this afternoon to 9 PM PDT
      this evening for zones 34>36-51. (See LAXNPWLOX).
     Wind Advisory in effect from 1 PM this afternoon to 3 AM PDT
      Friday for zones 39>41-52-87. (See LAXNPWLOX).
     Wind Advisory in effect from 4 PM this afternoon to 3 AM PDT
      Friday for zones 53-54. (See LAXNPWLOX).
     Wind Advisory in effect from 7 AM this morning to 3 AM PDT
      Friday for zone 59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 645-650-655-670-673-676. (See LAXMWWLOX).



No significant hazards expected.



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