Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 182247

National Weather Service Eureka CA
247 PM PST Sun Feb 18 2018

.SYNOPSIS...A cold storm system will bring rain and snow showers to
northwest California through early Monday morning. Some showers may
contain small hail. Behind this system a cold air mass settles
over the area. The coldest temperatures will be Tuesday morning.


.DISCUSSION...The upper level trough moving over the area is
bringing widespread showers to Humboldt and Del Norte counties.
Snow levels have dropped to around 2,000 feet as of noon. Snow
levels will continue to fall tonight to around 1,000 feet.
Additional snow accumulations of up to 3 inches are possible
tonight in Humboldt and Del Norte counties. Locally lower snow
levels are possible in the heavier showers. A few flakes are
possible at the coast towards morning, but nothing is expected to
stick. Along the coast below the snow level numerous showers are
producing small hail. This has been accumulating on roadways. One
of these storms produced a couple lightning strikes. So have added
a slight chance for thunder and small hail this evening. These
showers are expected to continue tonight and start to diminish
towards morning.

Monday isolated showers will diminish through the day.
Temperatures are expected to only warm into the 40s and snow
levels will be around 1,000 to 1,500 feet, but no significant
accumulation is expected. Monday night into Tuesday morning looks
like the coldest morning. Temperatures at the coast look to drop
to around 30 at the immediate coast with 20s just a mile two
inland. The hard freeze watch for the coastal areas looks to be on
track and confidence is growing that we will see these
temperatures. Farther inland temperatures will drop into the low
20s and teens. Single digit temperatures are possible in the
northern mountains. There will likely be some clouds around from
a system off the coast, but models have slowed down this system
and come into better agreement that these clouds will not impact
temperatures too much. Tuesday afternoon temperatures will warm
slightly, but most areas will remain in the 40s. Tuesday evening
and overnight a few showers and some clouds likely as the weak
system moves by just off the coast. Snow levels will be fairly
low, but only a dusting of snow is expected.

Wednesday the airmass starts to warm slightly with temperatures
warming back into to low 50s. Northwest flow persists and a few
sprinkles are possible with some clouds around. Thursday into the
Weekend the models are showing additional systems moving over the
area from the northwest. There is not very good agreement in the
models on these systems yet. However, there is reasonable
confidence that temperatures will be fairly cool and there will be
periods of light rain and snow. MKK


.AVIATION...An active day of showers at the coastal terminals
today will continue trough the evening before diminishing in
intensity and coverage later tonight.  The showers have and will
bring brief periods of mvfr conditions otherwise sites will mainly
observe VFR conditions through the next taf cycle. Some interior
valley locations sheltered from the north winds could see some ground
fog develop very early tomorrow morning.


.MARINE...Gusty Northwest to north winds will continue through
tomorrow across all waters. Some of these winds are also enhanced
from passing showers...although the shower activity should diminish
over night. Meanwhile, a large swell from the northwest will move
through the waters this evening through Monday morning. The
combination of steep wind-driven seas and the arriving swell will
result in very large and hazardous seas with combined wave heights
reaching 20 to 25 feet throughout much of the waters. As a result, a
Gale Warning remains in effect for the outer waters from late this
morning through Monday afternoon. Hazardous Seas Warning has been
issued for the nearshore waters of Humboldt, Del Norte, and
Mendocino counties. Winds will steadily decrease through the day
Tuesday, allowing seas to slowly subside.  Tuesday and Wednesday,
north winds of 15 to 20 kt will maintain somewhat elevated seas,
likely with wave heights between 7 and 9 feet. However, north winds
will increase again Thursday through the end of the week, resulting
in the buildup of steeper seas that will last through at least the
end of Friday. /KAR/JT


CA...Hard Freeze Watch from late Monday night through Tuesday morning
     for CAZ101-103-109.

     High Surf Advisory from 1 AM to noon PST Monday for CAZ109.

     Winter Weather Advisory until 4 AM PST Monday for CAZ102-104>108.

     High Surf Advisory from 7 PM this evening to 4 AM PST Monday for

NORTHWEST CALIFORNIA COASTAL WATERS...Gale Warning until 3 PM PST Monday for PZZ470-475.

     Small Craft Advisory for winds until 3 PM PST Monday for PZZ450-

     Hazardous Seas Warning until 3 PM PST Monday for PZZ450-455.



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