Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 180622
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
1022 PM PST Fri Nov 17 2017

...Aviation discussion updated...

.SYNOPSIS...

Surface high pressure settling in over the Central Rockies will
bring weak Santa Ana winds to portions of Southwest California
Saturday. The dry and cool air mass will also support the first
freeze of the season for cooler interior areas this weekend. A
ridge of high pressure building into the region early next week
will bring a warming trend with record heat possible by
Thanksgiving.

&&

.SHORT TERM...(FRI-MON)

High pressure at the surface is starting to build into the Great
Basin this evening as a cold front exits the region. The front,
now stretching from Central Arizona into Northwest New Mexico and
Southeastern Colorado will continue to march east. Surface high
pressure, driven by the cold air mass in the Great Basin
will continue to strengthen into Saturday, while an inverted
surface trough develops over the Southern California Bight and
along the Southern California Coast.

Onshore flow is weakening this evening as the northerly surface
pressure gradient develops, before turning northeast overnight.
Locally gusty northwest to north winds have developed across
Southern Santa Barbara County this evening. These winds are not
expected to become widespread this evening.

As the pressure gradient become northeast later tonight and into
Saturday morning, marginally gusty Santa Ana winds will develop.
A wind advisory was added for mainly Western Los Angeles and
Eastern Ventura Counties where these winds will be strongest.
Gusts between 35 mph and 45 mph will develop through Saturday
morning. Motorist traveling across Southern California should
exercise caution due to the possibility of gusty cross winds.

A dry air mass moving into the region behind the front will allow
for wind-sheltered areas to radiative cool more efficiently
tonight and again on Saturday night. Frost advisories and freeze
watches posted by the previous shift look agreeable and no changes
were made.

*** FROM PREVIOUS DISCUSSION ***

On Monday the ridge remains in place but some moisture from a
storm well to the north will manage to get through and increase
clouds across the area, especially north of Pt Conception. There`s
too much subsidence for any precip so rain chances have been
removed, but there will still be a fair amount of clouds,
especially up north. And temps Monday will be similar to Sunday.

.LONG TERM...(TUE-FRI)

The ridge will build even stronger Tue and peaking Wed and
Thanksgiving. Gradients will trend offshore again and peak
Thursday but just enough for some locally gusty but sub-advisory
level Santa Ana winds. Temps will make a noticeable jump Wed into
the mid to high 80s for many LA/Ventura valleys and some coastal
areas as well. Slightly cooler up north but still well above
normal. Perhaps even a few isolated lower 90s on Thanksgiving day.
Cooler but still warm and dry going into the weekend.

&&

.AVIATION...18/06z.

At 0530z at KLAX... there was a weak inversion based around 900
feet. The top of the inversion was around 1600 feet with a
temperature of about 16 degrees Celsius.

Overall... Moderate to high confidence in the current TAFs. There
will be periods of moderate wind shear and turbulence at KOXR...
KCMA... KSMO... KVNY... and KBUR through 15z. During the 10z-17z
period there is a sixty five percent chance of IFR/MVFR conditions
at KLGB and a forty percent chance of IFR/MVFR conditions at
KPRB... KSMO... and KLAX. Otherwise and elsewhere VFR conditions
will prevail.

KLAX... Moderate to high confidence in the current TAF. There is a
forty percent chance of IFR/MVFR conditions during the 10z-17z
period. Otherwise VFR conditions will prevail. There is a ten
percent chance of east winds to ten knots 19/09z-16z... otherwise
no east winds greater than seven knots are expected during the
forecast period.

KBUR... Moderate to high confidence in the current TAF. There is
a twenty percent chance of moderate wind shear and turbulence
through 15z. There is a twenty five percent chance of MVFR
conditions during the 12z-17z period. Otherwise VFR conditions
will prevail.

&&

.MARINE...17/900 PM.

Northwest winds across the Outer Waters will continue to diminish
as surface high pressure to the north slides into the Great Basin
later tonight. Winds will subside across the Outer Waters later
tonight, while winds will start increase nearshore on Saturday
morning. There is a 50 percent chance that a Small Craft Advisory
could be added for the nearshore waters from Rincon Point to
Santa Monica. At the minimum, locally gusts winds and choppy seas
will develop on Saturday across the Inner Coastal Waters.

Gusty winds will increase again between Saturday evening and
Sunday afternoon. Small Craft Advisories may need to be issued
sometime between Saturday evening and Sunday morning as winds look
to increase to advisory levels during this period. Winds will
remain at Small Craft levels across the Outer Waters through late
Monday night or early Tuesday morning.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory in effect until 8 AM PST Saturday for zones
      37-38. (See LAXNPWLOX).
     Freeze Watch in effect from late Saturday night through
      Sunday morning for zones 37-38. (See LAXNPWLOX).
     Wind Advisory in effect until 2 PM PST Saturday for zones
      44>46-53-54-88-547. (See LAXNPWLOX).
     Freeze Warning in effect until 8 AM PST Saturday for zone 59. (See LAXNPWLOX).
     Hard Freeze Watch in effect from late Saturday night through
      Sunday morning for zone 59. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Saturday for
      zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(MON-FRI)
No significant hazards expected.

&&
$$

PUBLIC...Hall/MW
AVIATION...Kj
MARINE...Hall
SYNOPSIS...Munroe

weather.gov/losangeles



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