Small Craft Advisory 29, NWS Los Angeles, CA

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

.SYNOPSIS...
The showers will linger into the evening. A low should move into
Nevada tonight resulting in gusty winds and possible
precipitation for the northern foothills and mountains into
Wednesday night. The clouds will decrease Thursday and
Friday...with temperatures about normal into early next week. A
storm system could bring rain to the area Saturday night and
Sunday. The precipitation may continue into early next week.

&&

.SHORT TERM...(TDY-FRI)

The light rain showers continue to impact SBA and Ventura
Counties this afternoon, but still expecting these to taper off
this evening as the flow shifts to northwesterly. A little
uncertain honestly if the shut off will be closer to 4pm or
midnight. Other areas may see a light shower or two into the
evening.

The trough that is causing all this light rain will move into
northern California on Wednesday...which shift the flow from
southwesterly to northwesterly. Winds at the surface will turn
more northerly as early as tonight...then increase
Wednesday...and stay gusty through Thursday night. The wind prone
areas (like the I-5 Corridor & Antelope Valley & southern SBA
County) should see advisory level gusts to 50 mph. Will be
issuing that advisory shortly. The north flow will also help clear
things out Wednesday and Thursday on the coastal side of the
mountain ranges...with periods of sunshine and highs in the 60's.
On the backside however moisture will pile up starting tonight and
result in a number of showers...especially from the Tejon Pass to
Cuyama. While snow levels should stay above 5,000 feet tonight
into Wednesday...they still look to lower to around 3,500
Wednesday night into Thursday. This should result in light snow
over interior roadways (including the I-5 Tejon Pass, Highway 166
and Forest Road 95)...which could accumulate and cause hazardous
road conditions.

By Friday, the flow turns slightly more easterly, which will kill
the north slope showers. This will also bring an extra dose of
warming...but the airmass will remain cold and temperatures will
continue to be at or below normal.

.LONG TERM...(SAT-TUE)

Rain still looks likely over the weekend...with Saturday night and
Sunday looking like the main window of opportunity. A weak trough
currently over the Aleutian Islands will drop into the northern
California waters on Saturday and join forces with a low currently
1600 miles west of San Francisco. This new system looks to push
through central California on Sunday.

While there is growing confidence for rain, the details remain
fuzzy. There is a real potential for moderate rain in the
0.50-1.50 inch (in 6 hours) neighborhood which is what the GFS is
showing, but the 12Z ECMWF came in frustratingly light. Based on
the deepness of the low would have to lean toward the wetter
solution, but the ECMWF has been performing better than the GFS of
late...leading to some shoulder shrugging.

Computers are projecting another low working down the coast which
would slow the progression of the Sunday system. If this scenario
plays out, temperatures would remain below normal with ample
clouds and general chances of showers through Monday or Tuesday.
Not putting too much stock in this just yet...as there is just too
much run-to-run variability with the weekend.

&&

.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...21/200 PM...

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 3 PM PST Wednesday for
      zones 34-35. (See LAXCFWLOX).
     Wind Advisory in effect from 3 PM Wednesday to 10 AM PST
      Thursday for zones 39-52>54. (See LAXNPWLOX).
     High Surf Advisory in effect from noon Wednesday to 9 PM PST
      Thursday for zones 40-41-87. (See LAXCFWLOX).
     Wind Advisory in effect from 3 PM Wednesday to 3 AM PST
      Thursday for zone 59. (See LAXNPWLOX).
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...(FRI-TUE)
More rain and wind is expected over the weekend.

&&

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

weather.gov/losangeles