Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 211253

National Weather Service Eureka CA
553 AM PDT Wed Mar 21 2018

.SYNOPSIS...A cold front will approach today bringing increasing
rain and gusty winds for tonight through Thursday morning. A
series of disturbances in the colder air behind the front will
generate bouts of rain with moderate to heavy snow above 2000
feet Thursday night through Saturday evening.


.DISCUSSION...An upper trough offshore will continue to pump
warm/moist air into the region from the southwest today. Even
though the radar has not been showing much activity through the
night, surface reports indicated light rain or drizzle still
occurring. The precip will continue to be light and spotty
through most of the morning...before southerly winds and light to
moderate rain starts to ramp up late in the day into this evening
in advance of an offshore cold front. The front will generate
widespread rain and perhaps a period of heavy rain late tonight
into early Thursday morning.

There is a concern that snow levels will rapidly fall behind the
front early Thursday morning. BUFKIT profiles certainly indicate
the potential for a few inches of snow early Thursday before the
precip rapidly winds down through the day. This will need to be
watched for a short duration snow advisory.

After a brief break in the precip Thu afternoon and evening,
another front is slated to rapidly approach Thu night, bringing
yet more widespread rain and mountain snow. Significant snow
is expected above 2000 to 3000 feet with this colder storm on
Friday. The snowfall will likely impact travel over the mountain
passes Friday morning. Warmer roads and a higher March sun angle
may result in snow rapidly turning into slush Friday afternoon,
however. For now, we call attention to this winter weather travel
hazard in a weather story graphic and a hazardous weather
statement. An advisory or warning for heavy snow will need to be
considered as this event grows closer.

Another low pressure system will drop down from the northwest
on Saturday bringing the potential for more significant snowfall
above 2000 feet. The GFS, ECMWF and NAM were still not in
fabulous agreement on the track of this low, so confidence is
only moderate at this time. Guidance continue to indicate precip
potential winding Sat night and Sunday. Shallow instability will
linger on the backside of the upper trough on Sunday. Thus will
maintain at least a slight chance for showers for Sunday.

Upper ridging/warming aloft and offshore wind flow should result
in drier conditions Sun Night and Monday. A frost advisory or
freeze warning may be necessary for coastal areas and for interior
portions of Mendocino county Sun night and Monday morning if
skies clear out and it does not fog up.


.AVIATION...The forecast is a bit tricky today as southerly
flow has returned to the region. This may hinder rain development
this morning even though the atmosphere is quite moist. I have
opted to keep either dry conditions or showers in the short term
part of the forecast with light to moderate rain expected late in
the TAF cycle. Conditions will generally bounce between VFR and
MVFR between showers, except for valleys where moisture has a
better chance at remaining trapped which would support IFR


.MARINE...Light winds and slowly subsiding seas are forecast for
this morning as we wait for the arrival of the cold front this
afternoon. This will bring increasing winds through the evening with
occasional near gale force gusts forecast for late tonight. The
strongest winds will occur beyond 10 nautical miles and around Cape
Mendocino thus Small Craft Advisories have been hoisted across the
marine zones through Thursday morning. Winds behind this front
sharply turn to the northwest early Thursday morning but switch back
to the southwest by the evening. Seas will begin to build after a
second round of strong southerly winds on Friday.



10 PM this evening to 5 AM PDT Thursday for PZZ450. Small Craft
Advisory from 5 PM this afternoon to 11 AM PDT Thursday for
PZZ455-470. Small Craft Advisory until 4 AM PDT early this morning
for PZZ475. Small Craft Advisory from 5 PM this afternoon to 2 PM
PDT Thursday for PZZ475.



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