Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 241139

National Weather Service Eureka CA
339 AM PST Sat Feb 24 2018

.SYNOPSIS...Light precipitation will spread south across the
region during Saturday. Heavier showers are forecast to occur
Sunday night into Monday, with several inches of snow possible for
elevations above 2000 feet. Additional showers and mountain snow
are expected Wednesday through Friday.


.DISCUSSION...Regional radar imagery showed light precipitation
spreading inland across Humboldt and Del Norte counties at 11Z.
This activity will continue to progress south and east into
portions of Trinity and Mendocino counties during the
morning...but, precip totals will become progressively light by
midday as forcing aloft exits east. By tonight, skies are forecast
to clear across much of the interior, which will favor subfreezing
temperatures and patchy freezing fog and/or frost.

Clouds will spread south once again during Sunday ahead of an
upper wave digging over the NERN PAC. This wave will enter NWRN CA
late Sunday night into Monday morning. Model guidance continues to
show very cold midlevel temperatures occurring within the core of
the upper trough. However, the heaviest precipitation is forecast
to occur ahead of the cold midlevel airmass. Thus, significant
snowfall occurring across mountain highway corridors appears to
be less probable at this time. In addition, the potential for
widespread coastal hail showers is more marginal based on current
model trends.

A stronger upper-level storm system is forecast to materialize
during the Wednesday through Friday time frame. Model output
indicates this system will impact the region in two phases. The
frontal phase will occur late Wednesday afternoon into the
evening, with strong southerly winds veering to westerly with the
frontal passage, potentially yielding strong gusts for exposed
coastal and ridgetop locations. In addition, heavy precipitation
appears probable along/ahead of the front. The second phase will
occur Thursday afternoon into Friday as very cold temperatures
aloft spread across the region with an occluded upper low. This
environment will result in a steep lapse rate/convective regime
accompanied by low freezing levels. Heavy mountain snow and
coastal hail will be possible as a result.


.AVIATION...MVFR conditions and periodic light rain will persist
at north coast air terminals through the morning hours as a weak
trough passes across the PAC NW. Conditions should improve for the
afternoon and evening hours as high pressure rebuilds behind the
trough. Conditions may start to deteriorate again as early as late
tonight as a new front moves toward the Oregon coast. VFR
conditions will likely prevail at KUKI through the period, however
brief MVFR cigs will be possible through the morning hours.


.MARINE...For the most part winds will remain sub-advisory today
through Sun. North winds are forecast to increase again on Mon
with gales possible over the southern waters by Mon night.

A short period NW swell will build to around 10 ft tonight and
fluctuate from 8 to 10 ft through Sun. A more substantial short
period NW swell should build Sun night into Mon. This swell will
combine forces with shorter period wind waves to produce seas
around 17 feet south of the Cape by Mon night.




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