770 
FXUS66 KLOX 180206
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 
706 PM PDT Fri Mar 17 2017

.SYNOPSIS...
Overnight fog and low clouds at the coast...otherwise partly 
cloudy into this weekend. A cooling trend will start on Saturday 
as the high exits. Then a low will bring possible precipitation 
from Monday into Wednesday night. On Thursday a high may build in 
on for a warming trend into Friday. Another storm system should 
approach by next weekend.

&&

.SHORT TERM...(FRI-MON)

Shallow marine lyr hanging tough along the coast and over the
coastal waters south of Pt Conception this afternoon. The ridge
over the west coast is expected to shift slowly east tonight and
Saturday, though probably not soon enough to generate any
significant lifting of the cloud bases. So expect another round of
dense fog tonight with little if any valley intrusion. 

Heights will be lowering through the day Saturday as the next
trough approaches. This combined with decent onshore trends should
produce several of degrees of cooling across the valleys and a few
degrees elsewhere.

Probably not too much change Sunday as there's very little change
in the upper pattern or gradients. 

Stronger onshore trends expected Monday as the trough gets closer
and the air mass cools. This should deepen the marine lyr, push 
clouds into the valleys and drop highs a few more degrees. A weak
cold front will be approaching the Central Coast Monday afternoon
but it looks like it should stay west of the coast through the 
day so no rain expected there until late Monday night.

.LONG TERM...(TUE-FRI)

Forecast after Monday still highly uncertain. ECMWF wasn't
available today but the GFS continues to wobble between minimal
and very minimal in terms of impacts and rainfall amounts on 
Tuesday. The 06z run was a little stronger and was in the quarter
to half inch category. The 12z run pushed the upper low even
farther north and the resulting cold front passage was even weaker
with amounts mostly under a tenth of an inch. There is a follow up
system on Wednesday but a lot of that energy was going south. Even
last night's EC run kept most of the fun south of LA County Wed.
Since models have consistently shown at least a little rain for
Tuesday the pops were left in the likely category, though it might
end up being a high pop/low qpf event. Pops also left unchanged
for Wed, mostly in the 30-40 range.

Both models favoring a dry day Thursday so pops were lowered and
precip removed from the forecast. The GFS and last nights EC both
slowed down the arrival of the Friday system to more like Friday
night into Saturday. This one appears to have a little more energy
and moisture with it but still a ways out there and lots of
uncertainty ahead of it.

&&

.AVIATION...18/0145Z.

At 0130Z, the marine layer was around 700 feet at KLAX. The top 
of the inversion was around 2400 ft with a temperature of 22 
degrees Celsius.

N of Point Conception...Low to Moderate confidence with 00z Tafs.
Not confident that VLIFR/LIFR cigs will develop at KSMX and KSBP.
40% chance that cigs will not develop. 40% chance cigs will
develop a couple hours +/- 2 hours. Should give way to MVFR vsbys
into the afternoon hours. 40% chance that VLIFR/LIFR cigs will not
develop at KPRB after 12z-16z.  

S of Point Conception...Moderate confidence with coastal taf sites
with VLIFR/LIFR cigs filling in most coastal TAF sites before 08z.
High confidence for VFR conds for inland taf sites over the next
24 hour period.

KLAX...VLIFR/LIFR cats are expected through 14z. 30% chance that
cigs could continue through 16z. Expecting MVFR vsbys otherwise
the remainder of Saturday. 30% chance of earlier cig improvement 
12-16Z as marine layer deepens.

KBUR...High confidence in VFR conditions through Saturday with 
light winds...with a 10 percent chance of LIFR cats after 14Z.

&&

.MARINE...17/100 PM.

Areas of dense fog with visibility less than one nautical mile 
will continue through Saturday morning especially nearshore. 
Mariners should be prepared for visibilities as low as a few 
hundred yards (under one quarter of a mile) at times...dangerously
hiding other vessels and land features. Dense fog issues should 
improve each day over the weekend. 

Confident of No Small Craft Advisories through the weekend.

A storm system will move through the area on Tuesday, with 
widespread gusty winds and choppy seas at times Monday and 
Tuesday. The rest of next week looks unsettled with chances of 
storms.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory in effect until 9 AM PDT Saturday for zone
      41. (See LAXNPWLOX).
PZ...NONE.

&&

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

&&

$$

PUBLIC...MW
AVIATION...Kaplan
MARINE...Kittell
SYNOPSIS...STu

weather.gov/losangeles