Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 171307

National Weather Service Eureka CA
507 AM PST Sat Feb 17 2018

.SYNOPSIS...An incoming storm system will bring rain and snow
showers to northwest California beginning late this afternoon
through early Monday morning. Snow levels will rapidly fall from
3000 feet Sunday to around 1000 feet early Monday morning. A
prolonged period of cold temperatures will persist into early next


.DISCUSSION...Beginning today, northwest California is in for a
switch in weather conditions as a cold upper trough digs over the
Pacific Northwest. Light rain will begin to impact the northern
reaches of the forecast area beginning this afternoon and gradually
shift southward through tonight. Showers will continue Sunday into
early Monday morning in the wake of the cold front. The arrival of
this colder airmass will cause snow levels to rapidly fall from 3000
feet Sunday morning to around 1000 feet Monday morning. Snow levels
will fall further on Monday however, precipitation will diminish.
Rainfall totals will not be particularly significant with 0.25-0.80
inches across Humboldt and Del Norte counties and around 1.25 inches
possible in the mountains of Del Norte. Accumulations will be
lighter across Mendocino and eastern Trinity counties ranging from a
few hundredths to nearly 0.20 inches. Snow accumulations will be
more impactful as snow levels drop on Sunday. Passes on Highways
199, 299, and 3 could see 2 to 5 inches which will make travel more
hazardous. Greater snow accumulations around 6 to 10 inches will be
possible above 4500 feet. A winter weather advisory has been issued
early Sunday through early Monday primarily for snow impacting
highway passes. In addition, small hail will be possible in
showers near the north coast although instability will remain
limited. Precipitation chances will diminish later Monday as dry,
polar air moves into the region. Widespread, cold temperatures
will impact much of the region early next week. Model guidance
suggests that that daytime temperatures will only reach the 40s
and low 50s with nighttime temperatures in the upper 20s possibly
extending to the coast. /KML


.AVIATION...More or less of the same on satellite imagery this
morning. High clouds are moving into the region with the associated
low pressure system arriving, but where there has been clear skies,
fog and low cloud have formed. Look for lowering clouds to arrive
later in the morning with MVFR conditions expected when the frontal
system passes through. Model soundings suggest IFR conditions could
be possible, but my confidence was not high enough to put them in
for the coastal TAF sites this morning.


.MARINE...Not much has changed in the marine forecast this morning,
with northerly winds briefly decreasing and wave heights subsiding
today. These conditions will be short lived though as a trough drops
into the Pacific Northwest. Strong northerly winds will return with
the trough which will create some steep wind waves. A couple of
swells will also be moving through the waters, with the largest one
of 15 to 20 feet arriving Sunday into Monday.


CA...Winter Weather Advisory from 4 AM Sunday to 4 AM PST Monday for

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from 9 PM this evening to 9 PM PST Monday
     for PZZ470.

     Small Craft Advisory from 7 AM Sunday to 9 PM PST Monday for

     Small Craft Advisory until 9 PM PST Monday for PZZ475.



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