000
FXUS66 KLOX 220138
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
638 PM PDT Mon May 21 2018

.SYNOPSIS...21/638 PM.

A series of low pressure systems moving over the state will bring
continued onshore flow and below normal temperatures through much
of the week. A deep marine layer will continue night through
morning low clouds and fog for the coast and valley areas. Any
shower activity should remain confined to the mountains through
Tuesday.

&&

.SHORT TERM (TDY-THU)...21/212 PM.

Very little afternoon clearing so far, and starting to see some
cumulus development over the Los Angeles and Ventura County
mountains. The chance of afternoon or early evening
thunderstorms isn`t zero, but its not a very high number. If a
thunderstorm forms over the LA mountains it will likely drift
into the Antelope Valley.

The low heights, strong onshore flow, and persisting cloud cover
have all worked to keep the temperatures down. Afternoon highs
will likely be 5-10 degrees below average. Today should be the
coolest of the week.

The upper low responsible for the overcast skies and drizzle will
move to the east on Tuesday. The marine layer will remain
essentially unchanged from today and and it will likely be
another overcast day south of Pt Conception. Expecting conditions
be be a bit better on the central coast, with the low clouds
clearing by late morning. There is enough moisture remaining that
the afternoon clouds expected over the Ventura County mountains
could lead to a light shower or two, so added that slight chance
into the forecast.

A weak ridge pops up for Wednesday, lowering the marine layer
and increasing the strength of the inversion. Onshore flow
will continue, but the strength should weaken a bit. Expecting
late morning clearing for all locations with a degree or so of
warming, but still a few degrees below normal.

Another upper level heading our way will drive the forecast for
the remainder of the week. On Thursday the system is expected to
be west of San Francisco and our area will be transitioning from
the weak ridge to the oncoming trough associated with the upper
low. Similar weather to Wednesday with maybe another degree of
heating.

.LONG TERM (FRI-MON)...21/213 PM.

The numerical models, which have been inconsistent, seem to think
the system will remain to our north. This solution includes a
110kt jet streak passing overhead on Friday along with some
vorticity that could mean showers at the start of the holiday
weekend. Did not add any at this time.

The extended forecast all plays out based on the track of the
upper level low. Right now that looks like the low moving to the
southeast on Saturday and dropping our heights. Unlike today we
don`t expect the extensive cloudiness, and the onshore flow will
be about half as strong so temperatures should remain about the
same as on Friday.  Look for a typical night through morning low
cloud pattern across the coasts and most of the valleys.

A ridge builds over the region Sunday and Monday and am
expecting some strong temperature gains along with the height
rises. Onshore flow remains fairly weak. If it all works out as it
looks now, then afternoon high temperatures will finally be above
normal by Monday.

&&

.AVIATION...22/0129Z.

At 00Z, a deep moist layer was up to around 4000 feet.

Low-to-moderate confidence in the current forecast. Highest
confidence exists in MVFR conditions redeveloping through 13Z at
coastal and valley terminals. There is a chance of IFR conditions
between 08Z and 16Z. MVFR to VFR conditions with ceilings at or
below 5000 feet could linger throughout Tuesday.

KLAX...There is a 30 percent chance of IFR conditions between 09Z
and 16Z. There is a 50 percent chance of MVFR conditions lingering
up to 2 hours longer than the current forecast, and possibly
throughout the period.

KBUR...There is a 30 percent chance of IFR conditions between 09Z
and 16Z. There is a 20 percent chance of VFR conditions developing
on Tuesday afternoon.

&&

.MARINE...21/201 PM.

For the Outer Waters, high confidence in Small Craft Advisory
(SCA) level winds continuing through late tonight. For Tuesday
through Thursday, winds and seas will remain below SCA levels. A
long period southerly swell will arrive Tuesday with mixed swells.
On Saturday, there is a 40% chance of SCA level winds, especially
across PZZ673/676.

For the Inner Waters, high confidence in current forecast. For the
waters north of Point Sal, SCA level winds will occur through this
evening then winds/seas are expected to remain below SCA levels
Tuesday through Friday. For the waters south of Point Conception,
winds and seas will remain below SCA levels through Friday. A
long period southerly swell will arrive over the waters with
locally rough harbor entrances from Tuesday afternoon through
Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect from Tuesday afternoon
      through Thursday evening for zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Tuesday for
      zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

Strong rip currents and elevated surf will linger at south-facing
beaches across Los Angeles and Ventura Counties.

&&

$$

PUBLIC...jld
AVIATION...Hall
MARINE...EB
SYNOPSIS...STu/Hall

weather.gov/losangeles




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