251 
FXUS66 KLOX 211817
AFDLOX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 
1017 AM PST Tue Feb 21 2017

...Aviation and Marine discussions updated...

.SYNOPSIS...

Light rain will linger today. A low will move into Nevada tonight
with breezy north winds and possible precipitation for the 
mountains through Wednesday night. The clouds will decrease into 
Friday...and temperatures should be about normal by the weekend. 
A storm should approach from the north on Saturday and spread 
precipitation by Sunday. The precipitation could continue into
Monday.

&&

.SHORT TERM...(TDY-THU)

A narrow band of mid-to-upper level moisture is showing up well 
on radar right now over Los Angeles County. While the radar looks
more ominous than it is (being high based) it is a bit of a
surprise, and leads to a better chance for some light but
measurable rain (under 0.10 inches) for LA County. Upped PoPs as 
a result. To the north, low level moisture is interacting with the
southwest flow aloft once again today. Radar for SLO to Ventura 
Counties is showing some low reflectivities, but this is very much
under- representing the rain because the moisture is so close to 
the ground. With steady light rain falling there now, upped PoPs 
to near 100 percent...though additional amounts will be light and 
mainly in the 0.10 to 0.25 inch neighborhood. The low- level 
nature of this rain will also make interior areas hard pressed to 
get rain as the mountains will block a lot of it, but a few 
showers could squeeze through. Rain still looks good to taper off 
quickly later today and tonight...but low confidence on exactly 
when as it could quickly shut off this afternoon or linger into 
the evening.

***From Previous Discussion***

An inside slider moves down the CA/NV line tonight. It is pretty
dry but it will shift the winds to the north which will pile up
clouds and a few showers on the north slopes. Otherwise skies
should turn partly cloudy across the coasts and vlys. Despite the
additional sunshine the max temps will fall a couple of degrees as
cold air filters in behind the trof. the winds will keep the
clouds and scattered showers going through the day. Snow levels 
will fall through the day but should remain above the Grapevine
pass level.

It looks like advisory level wind gusts will develop across the LA
VTA and SBA mountains as well as the Antelope Vly Wednesday night.
The winds will be strongest through the i-5 corridor. It will also
be gusty in the Santa Clarita Vly and the area either side of the
VTA/LA county border. Clouds and a few showers will remain on the
north slopes. Snow levels will get close to the pass levels.

The barest of ridges will move into the area Thursday. Skies will
be mostly sunny. It will remain breezy but right now it looks like
the winds will be below advisory criteria. Max temps will warm a
couple of degrees but will still be below normal.

.LONG TERM...(FRI-MON)

Both the GFS and the EC agree that dry zonal flow will be over the
state on Friday and Saturday. Skies will be mostly clear
Friday...but Saturday will see a slow increase in clouds as a new
system begins its run into the state. Max temps will increase each
day and Saturday will be the warmest of the next 7 with max temps
coming in only a degree or two below normals.

Both the EC and the GFS are in fair agreement that a cool upper
low embedded in the base of it much larger parent trof will rotate
down the coast and then into the center of the state. If the
current mdl forecast is right light rain will overspread the area
Saturday night. The cold front with moderate rain will move over
the area during the day Sunday. Showers will then move in behind
the front and keep the area wet Sunday night and Monday. Would
like to see a few more mdl runs before fully jumping on this rain
bandwagon as frequently there are changes to both timing and
intensity of these storms as the event draws closer.

&&

.AVIATION...21/18Z...

At 17z at KLAX... there was no notable inversion.

Overall... Moderate confidence in the current TAFs. The reduced
confidence is due to the variability of the CIGs and VSBYs and in
the timing of the passing storm. IFR/MVFR conditions will
generally prevail across the region through 20z-22z except for 
the Antelope Valley terminals. Conditions will improve through
01z-03z then diminish to MVFR conditions by 10z at most coastal 
and adjacent valley locations through 17z. Otherwise and elsewhere
VFR conditions will prevail.

KLAX... Moderate confidence in the current TAF. The reduced 
confidence is due to the variability of the CIGs and VSBYs and in 
the timing of the passing storm. A forty percent chance of MVFR 
conditions developing periodically through 21z. Conditions will 
diminish to MVFR 10z through 17z. Otherwise VFR conditions will 
prevail. No east winds above 5 knots are expected during the 
forecast period.

KBUR... Moderate confidence in the current TAF. The reduced 
confidence is due to the variability of the CIGs and VSBYs and in 
the timing of the passing storm. A forty percent chance of MVFR 
conditions developing periodically through 21z. Conditions will 
diminish to MVFR 10z through 17z. Otherwise VFR conditions will 
prevail.

&&

.MARINE...21/830 AM...

Small Craft Advisory (SCA) level seas will persist through 
tonight across the outer waters and along the Central Coast. 
Northwest winds will increase to SCA level across all coastal
waters on Wednesday and persist through Thursday night. Winds 
will diminish to below SCA levels on Friday then strengthen again 
on Saturday and likely reach SCA levels across the outer waters 
and along the Central Coast.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory in effect until 4 PM PST this afternoon
      for zones 34-35. (See LAXCFWLOX).
PZ...Small Craft Advisory for hazardous seas in effect until 3 AM
      PST Wednesday for zones 645-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(THU-MON)
Snow levels below 4,000 feet Wednesday night could result in 
light snow mountain and interior valley roads including the Tejon
Pass. Gusty north winds are expected Wednesday and Thursday which
will create hazardous road conditions and possible downed trees. 
More rain and wind is expected over the weekend.

&&
$$

PUBLIC...Kittell/Rorke
AVIATION...Kj
MARINE...Kj
SYNOPSIS...STu

weather.gov/losangeles