Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 162234

National Weather Service Eureka CA
234 PM PST Tue Jan 16 2018

.SYNOPSIS...Mainly dry conditions will occur across northwest
California through midday Wednesday. Thereafter, southerly winds
will strengthen ahead of a storm system during Wednesday
afternoon. This will be followed by an extended period of
precipitation Wednesday evening into Saturday. In addition, snow
levels will fall to 2500 feet Thursday night and Friday.


.DISCUSSION...A weak warm frontal boundary is expected to move
onshore this evening. So light rain or drizzle is possible,
especially in the higher elevations. The models have been fairly
inconsistent with this, so confidence is low. As this warm front
moves off to the northeast warm and breezy conditions will move
across the area on Wednesday. These winds will be fairly strong,
gusts of 35 to 45 mph along the coast and over the near coastal
ridges. The strongest winds are expected with front passage and
are expected to diminish after the front passes. So we have
shortened the duration of the wind advisory, otherwise it looks
like it is on track. The ridges may need an advisory Light rain
is expected to start early to mid afternoon along the coast.
Wednesday night the front moves through and brings moderate to
locally heavy rain. This will taper off Thursday morning. Most of
the precip with the main front will fall above 6,000 feet.

Thursday afternoon and overnight showers will increase as the cold
air aloft moves over the area. The heaviest showers are expected
to be in Humboldt and Del Norte county. Along the coast there is
the potential for small hail. This will bring the slight chance
for thunder as well. Snow levels are expected to drop to 2,500 to
3,000 feet Friday morning. Went a few hundred feet below the
model forecast snow levels as the heavy showers will likely drive
snow levels a bit lower. Issued a winter storm watch for areas of
Del Norte and Humboldt county over 3,000 feet. Some snow is likely
down to 2,500 feet, but confidence is low on the amounts. This
will need to be watched. This may need to be expanded to the
southwestern Humboldt and Trinity, but amounts to only at
advisory levels so will hold off on this for now.

Saturday high pressure starts to build into the area briefly.
Snow levels will rise and the showers will diminish. The next
system is expected to start to move into the area Saturday night
into Sunday. This front slowly moves across the area and has the
potential to bring heavy rain to the area. Snow levels look to be
above most major passes for the heaviest precip, but confidence
is low on how high they will be. MKK


.AVIATION...Coastal terminals north of the Cape Mendocino became
VFR by middle morning...even as high clouds continued streaming
across the region. Plenty of low level moisture persisted over
Mendocino interior valleys through the afternoon: UKI was a
revolving cycle of MVFR-IFR as light shallow rain and moisture
continued over the valley. At the Coast: large surf and westerly
light winds at ACV brought CIG/VIS tumbling into IFR at noon due
to haze/sea spray. The remainder of the TAF period (through
Wednesday afternoon) will see increasing pre-frontal clouds that
will gradually lower. This evening: warm frontal drizzle this
evening is possible at the far NW Coast. Also, southerly winds
will increase overnight as the cold front advances. Models show
LLWS possibilities at CEC and ACV by Wednesday afternoon. Inland
valley areas can expect low CIGS and VIS once again the morning.


.MARINE...Very active marine sea state and weather will be in store
for NW California waters over the next few days. A moderate cold
front will move across the coastal waters on Wednesday accompanied
by gale force southerlies across the northern outer waters while the
inner waters approach gale force status. Along with the wind and
increasing wind chop...a long period large westerly swell will also
move across the waters late Wednesday and Thursday.  Peak significant
wave heights will approach 20 to 24 feet at around 20 seconds and
persist through Thursday. Due to the significant swell, a Hazardous
Seas Warning remains in affect from early Thursday morning through
Saturday morning.

.SURFZONE...The large long period westerly swell mentioned above will
arrive to the coast on Thursday.  Swell heights offshore should range
between 20 and 22 feet but when the swell reaches the shore...resulting
waves are expected to break near 25 to 30 ft.  This falls within our High
Surf Warning criteria thus a Warning is now in effect for Thursday.
Timing of peak waves looks to occur from early Thursday morning
through the afternoon so there will be some good opportunities to
view the surf. Of course extreme caution should be exercised as
higher run up waves are always possible.


CA...High Surf Warning from 10 PM Wednesday to 10 PM PST Thursday for

     Winter Storm Watch from Thursday evening through Friday evening
     for CAZ105-106.

     Wind Advisory from 11 AM to 8 PM PST Wednesday for CAZ101.

     Winter Storm Watch from Thursday afternoon through Friday
     evening for CAZ102.

    Small Craft Advisory until 4 AM PST Thursday for PZZ450-475.

     Hazardous Seas Warning from 4 AM Thursday to 10 AM PST Saturday
     for PZZ450-455-475.

     Small Craft Advisory until 3 PM PST Wednesday for PZZ455.

     Small Craft Advisory until 7 AM PST Wednesday for PZZ470.

     Gale Warning from 7 AM to 10 PM PST Wednesday for PZZ470.

     Hazardous Seas Warning from 10 PM Wednesday to 10 AM PST
     Saturday for PZZ470.



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