Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 181641
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
941 AM PDT Wed Oct 18 2017

.SYNOPSIS...
A cooling trend will continue through Friday as a series of weak
troughs moves over the region. A warming trend will develop over
the weekend as offshore flow develops across the region. Record
heat is forecast for early next week when offshore flow combines
with strong ridging aloft to bring a hot air mass to the area.
Cooling is possible for the latter part of next week.

&&

.SHORT TERM...(TDY-FRI)

A weak short wave along with some mid/upper level moisture moved
through overnight with basically zero impact and we`re now left
with a lot of sunshine. However, west/east onshore trends have
accelerated and the lower levels have cooled off quite a bit as
the LAX profiler is showing 4-8 degrees of cooling in the lower
3000`. Cooling trend expected to continue through Friday as a cold
upper trough moves into the Pacific NW. A dying cold front will
wash out before reaching the Central Coast Friday but we`ll see
some clouds from it along with a deepening marine layer.

Gusty Sundowner and I5 corridor winds expected the next few
evenings though they should be a little weaker tonight and mostly
below advisory levels. Behind the trough passage Friday evening
north gradients will tighten up and upper level support will
provide the necessary boost to push winds at least into advisory
levels for those areas.

.LONG TERM...(SAT-TUE)

The flow will turn offshore on Saturday as a cold air mass
settles into the Great Basin behind the trough currently in the
Gulf of Alaska. Surface high pressure will build into the Great
Basin through the weekend. A warming and drying trend will take
shape through the weekend and into early next week. Monday and
Tuesday will likely be the warmest days of the period when
offshore flow teams up the ridge axis aloft to warm the air mass
additionally. Temperatures have been nudged higher across the area
for Monday and Tuesday with values about 3-5 degrees above MOS
guidance for Monday and Tuesday. Record heat is forecast for
Monday and Tuesday as even MOS guidance values are near or above
record levels for Monday and Tuesday.

Gusty offshore winds cannot ruled out during this period either.
ECMWF solutions are stronger with the surface pressure pattern
relative to the GFS. GFS winds suggest 20-25 knots at 850 mb,
strong enough this far out. Confidence continues to grow for
gusty Santa Ana Winds this weekend.

&&

.AVIATION...18/1025Z...

At 1015Z, the marine inversion at KLAX was based at around 800
feet. The top of the inversion was 2300 feet with a temperature
of 28 degrees Celsius.

Overall, moderate to high confidence in 12Z TAF package. High
confidence in valley/desert TAFs as VFR conditions will prevail
through the period. For coastal TAFs, high confidence in VFR
conditions through this evening then moderate confidence in return
of CIG/VSBY restrictions tonight.

KLAX...moderate confidence in 12Z TAF. High confidence in VFR
conditions through this evening. For tonight, moderate confidence
in return of CIG/VSBY restrictions, but low confidence in flight
category (could range from IFR to VLIFR) and timing (arrival time
could be +/- 3 hours of current 07Z forecast).

KBUR...high confidence in 12Z TAF as VFR conditions will prevail
through the period.

&&

.MARINE...18/900 AM...

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level winds are expected to continue today
through Sunday. There is a 40% of Gale force winds Friday and
Saturday.

For the Inner Waters, moderate confidence in current forecast. For
the waters north of Point Sal, there is a 30% chance of SCA level
winds this afternoon/evening then a 60% chance of SCA level winds
each afternoon/evening Thursday through Saturday. For the waters
south of Point Conception, there is a 50% chance of SCA level
winds across western portions of zone 650 this afternoon and
evening then a 70% chance of SCA winds Thursday and friday in the
afternoon and evening for both zones 650 and 655.

A large storm off western Canada will generate 40 foot seas in
that area. This will produce a large long-period NW swell, moving
into our waters by Friday. Seas up to 15 feet are likely, with 20
foot seas possible across the outer and northern waters. There
will likely be dangerous breaking waves on the Central Coast
through the weekend with dangerous conditions in/near harbors.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect from Friday morning through
      Friday evening for zones 34-35. (See LAXCFWLOX).
     Beach Hazards Statement in effect through Thursday afternoon
      for zones 40-41. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Thursday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(FRI-TUE)
Hot temperatures and elevated fire weather conditions are
expected Sunday into early next week as another Santa Ana wind
event develops. Record heat is possible for Monday and Tuesday.
Large surf and strong rip currents is expected to develop at
Central Coast beaches between Friday and Sunday.

&&

$$

PUBLIC...MW/Hall
AVIATION...RAT
MARINE...Sweet
SYNOPSIS...Hall

weather.gov/losangeles



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