Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 280011 AAA
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
511 PM PDT Sun May 27 2018

updated aviation discussion

.SYNOPSIS...27/1042 AM.

A weak ridge building in aloft will support a warming trend through
Tuesday with less in the way of night to morning low clouds
across coastal areas. A trough of low pressure pushing into the
West Coast will support a return to more widespread night to
morning low clouds with cooler conditions by Thursday.

&&

.SHORT TERM (TDY-WED)...27/159 PM.

Its mostly clear and 72 degrees in downtown Los Angeles right now,
on its way to a near-normal afternoon high. The winds will pick
up again this afternoon on the Santa Barbara south coast, but
should remain below advisory strength.

Looking at the big picture, there is an area of closed circulation
around a low pressure system near the northern Nevada-Utah border.
The LOX area is at the southern extent of the cyclonic flow around
this system and will see upper level winds shifting from the
northwest to more of a westerly flow as the system continues to
move off to the east. Heights will rise from 578DM today to about
583DM on Monday and Tuesday bringing warming, especially to
interior areas away from the sea breeze.

The LAX-DAG gradient remains about the same tomorrow and Tuesday
so the sea breeze should be roughly the same as today`s. However,
the increased sunshine and heights will cause high temps to trend
higher. Downtown LA should be in the high 70s by Tuesday and the
Antelope Valley and norther SLO County will be in the mid-90s.

The marine layer was around 2500 ft deep this morning with a very
weak inversion. Expect night through morning low clouds to
continue through Tuesday, but the marine layer depth should lower
to around 1500 ft Monday and below 1000 ft on Tuesday.  With the
stronger inversion expected, low clouds should become more
organized and may not scour out to the coast until early afternoon
hours.

Another broad upper level trough will deepen as it approaches the
California Coast Tuesday night into Wednesday. 500mb heights will
drop from 583 DM on Tue to 575 DM by Wednesday night. Strong
onshore winds will accompany the trough as models forecast a
gradient over 7 mb. Winds advisories are likely for Wednesday and
Thursday.  Expect significant cooling from Tuesday to Wednesday.

.LONG TERM (THU-SUN)...27/210 PM.

The coolest day should be on Thursday with the trof axis over the
region and a deep marine layer in place. Clouds should linger
well into the afternoon hours with a possible reverse clearing
scenario. High temps will be below normal.

The models diverge on Friday as the GFS continues to develop the
trough into a cutoff low system to our south which quickly
transitions to the east and lets ridging return by Sunday. The EC
keeps a more broad trough over the area through Monday. Splitting
the difference led to the forecast with seasonal temperatures. If
that pop up ridge does develop then is could be considerably
warmer next weekend that the current forecast.

&&

.AVIATION...28/0008Z.

At 2323Z, the marine inversion at KLAX was around 900 ft deep. The
top of the inversion was around 4100 feet with a temperature of 16
deg C.

Moderate confidence overall in the 00Z TAFs. Low clouds with
IFR/MVFR conditions are expected to develop at the coast and
adjacent vly airfields with the onset of low clouds ranging from
around 03Z at KSMX to 12Z at KSBA. The low clouds are expected to
clear to VFR at these airfields later Mon morning to early
afternoon, except linger thru the afternoon at KOXR. Confidence is
high that the low clouds will form, but there is uncertainty in the
timing between flight cats and the timing of the development of the
low clouds and clearing to VFR on Mon, all of which could be off +/-
one to two hours. Otherwise, VFR conditions can be expected thru Mon
afternoon.

For KPRB, KWJF and KPMD, there is hi confidence in VFR conditions
thru the TAF period.

KLAX...Moderate confidence overall in the 00Z TAF. Low clouds and
MVFR conditions are expected to develop at the airfield by 05Z this
evening then persist thru about 21Z Mon. There is high confidence
the low clouds will affect the airfield during the period, but there
is uncertainty in the timing of the development and clearing of the
low clouds which could be off +/- one to two hours. Otherwise, VFR
conditions can be expected thru early Mon evening, with good
confidence that MVFR cigs will move back in by 03Z Mon evening.

KBUR...Moderate confidence overall in the 00Z TAF. Low clouds and
MVFR conditions are expected to develop at the airfield by 10Z late
tonight then persist thru about 17Z Mon. There is high confidence
the low clouds will affect the airfield during the period, but there
is uncertainty in the timing of the development and clearing of the
low clouds which could be off +/- one to two hours. Otherwise, VFR
conditions can be expected thru Mon afternoon.

&&

.MARINE...27/221 PM.

Across the outer waters, high confidence in SCA conds through
late tonight. Conditions are expected to remain below SCA levels
Monday through Monday night, with a 40% chance of SCA level winds
across the northern two outer waters zones Tuesday afternoon and
night. SCA conds are likely across all the outer waters Wednesday
through Friday.

Across the northern inner waters, there is a 40% chance of SCA
level winds late this afternoon and evening. Otherwise, SCA
conditions are not expected through Wednesday morning, with SCA
level winds likely late Wednesday afternoon through Friday.

Across the inner waters south of Pt Conception, SCA conditions
are not expected thru Wed night. There is a 40% chance of SCA
winds Thursday and Friday.

Choppy short period seas will continue through the holiday weekend
but should slowly subside.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

Strong rip currents and elevated surf will be possible at Central
Coast beaches Wednesday through early Thursday.

&&

$$

PUBLIC...jld
AVIATION...Sirard
MARINE...Smith
SYNOPSIS...Munroe

weather.gov/losangeles



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