Area Forecast Discussion
Issued by NWS Eureka, CA

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410
FXUS66 KEKA 221256
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
456 AM PST Thu Feb 22 2018

.SYNOPSIS...Showers will spread south across the region Thursday
morning and afternoon. Accumulating snow will be likely for
elevations above 1000 feet. In addition, showers and isolated
thunderstorms may produce accumulating small hail along the coast.
Otherwise, clearing skies Thursday night will favor very cold
temperatures by Friday morning. Additional showers and mountain
snow will be possible this weekend into early next week.

&&

.DISCUSSION...Thursday morning satellite imagery shows a
blossomingzone of ascent spreading south across western Oregon.
The leading edge of this ascent was entering Del Norte and
Humboldt Counties as of 12Z, and will continue to spread south-
southeast across Trinity and Mendocino counties during the
remainder of the morning. Satellite and regional radar imagery
indicate precipitation is showery/convective in nature, which is
further supported by isolated lightning strikes occurring over
SWRN Oregon. Model forecast soundings show the environment over
NWRN CA becoming marginally unstable through the morning. Given
these trends, a slight chance of thunderstorms has been introduced
for coastal areas and the adjacent ocean waters. Accumulating
small hail will be possible with stronger showers and storms.

Low freezing levels will accompany the showers spreading south
across the region...as evident by snow reported at Brookings at
12Z. The cold airmass, combined with convectively and
orographically enhanced precipitation rates, will favor 1 to 3
inches of snow above 1000 feet over much of Del Norte, Humboldt,
and Trinity Counties through this afternoon, with localized
amounts from 3-5 inches possible. Thus, the inherited Winter
Weather Advisory has been expanded into western and northern
portions of Trinity County.

In addition to hazardous precipitation, north-northwesterly winds
gusting to 35 mph will be possible for exposed coastal and
ridgetop locations as low pressure deepens this afternoon over
CNTRL CA and NV. Winds are forecast to subside this evening as low
pressure exits east. As that occurs, clouds are forecast to clear
the region, which will favor strong radiational cooling across
the region (further enhanced by snow covered ground). This will
support very cold temperatures Friday morning, with interior areas
falling into the teens and 20s, and locations near the coast
experiencing temperatures from 25-30 F. Therefore, a Hard Freeze
Watch for portions of the Humboldt and Mendocino coasts is on
track...and has been expanded to include parts of coastal Del
Norte.

Beyond Friday...the WRN CONUS will continue to experience
persistent large-scale troughing, with embedded smaller scale
waves moving southeast across NRN CA. This will support the
maintenance of slightly below normal temperatures, as well as
periodic episodes of showers and mountain snow. At this time, the
most significant precipitation episode is forecast to occur
Sunday night into Monday, which could necessitate additional
winter weather headlines.

&&

.AVIATION...Low clouds have rapidly thickened from the N across
the Redwood Coast as low pressure drops into the area. Light rain
has made its way to KCEC and will arrive at KACV shortly. After a
brief period of stratiform rain, the rain will become more showery
in the unstable air. Have continued the inclusion of small hail
for the Redwood Coast during the morning hours. Have also included
vicinity thunder at KCEC during the morning hours, although the
chances are fairly low. Clouds are forecast to scatter out along
the coast during the afternoon and evening, with clouds lingering
over the coastal mountains inland from Humboldt Bay to near Cape
Mendocino as N flow piles up low level moisture. KUKI will also
see increasing and lowering clouds this morning with the potential
of some very light rain and/or snow from late morning into the
early afternoon.

Surface winds will increase out of the NW to N by late morning
with gusts of 20 to 25 knots possible at all terminals. Winds will
drop back off by late evening, although above the surface will
continue around 25 knots through the end of the TAF cycle. /SEC

&&

.MARINE...N winds will increase through the day today, and
headlines remain unchanged with a marginal Gale Warning for the
outer waters and a Small Craft Advisory for the inner waters.
Isolated showers will be capable of producing small hail and a few
lightning strikes over the N waters today. N winds will decrease
late tonight and during the day on Friday from N to S with lighter
NW winds expected for the upcoming weekend. NW winds are forecast
to increase again by early next week.

A NW swell with a period between 13 and 15 seconds will continue
to decay through today. Another NW swell will enter the waters
Thursday afternoon and decay through the end of the weekend.
Larger NW swell will persist through much of the period as
stronger N winds develop farther offshore the local marine area.
/SEC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Hard Freeze Watch from this evening through Friday morning for
     CAZ101-103-109.

     Winter Weather Advisory until 4 PM PST this afternoon for CAZ102-
     104>108.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
     6 AM PST early this morning for PZZ470.

     Gale Warning until midnight PST tonight for PZZ470.

     Small Craft Advisory from 9 AM this morning to 3 PM PST Friday
     for PZZ455.

     Small Craft Advisory until midnight PST tonight for PZZ450.

     Small Craft Advisory until 9 AM PST this morning for PZZ475.

     Gale Warning from 9 AM this morning to 6 AM PST Friday for
     PZZ475.

&&

$$

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