Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 191204
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
504 AM PDT Thu Oct 19 2017

.SYNOPSIS...A frontal system will bring increasing southerly winds
and widespread rain to the CWA today. A broad trough will be
passing through the Pacific Northwest which will allow for
lingering showers through the weekend. By early next week, high
pressure will build over the area leading to warm and dry weather.

&&

.DISCUSSION...
.SHORT TERM... (Today through Friday) We await the arrival of a
frontal system this morning which will bring increasing southerly
winds and widespread rainfall to northwest California. The
strongest winds are forecast to be north of Mendocino County,
especially for ridges above 1000 feet in Del Norte and Humboldt
counties and coastal communities in Del Norte. Gusts up to 40 to
45 mph are expected for these locations, resulting in a Wind
Advisory from 11AM to 5PM, while other areas remain below
criteria but remain breezy. Winds may cause branches and unhealthy
trees to fall, loose objects to topple over, and difficult
driving conditions for high profile vehicles. As for total
rainfall amounts through Friday, Del Norte County can expect to
see 1.50 to 2.0 inches with higher amounts possible in the ridges.
Humboldt County will also see a decent amount of rain with
totals ranging from 0.50 to 1.50 inches. Trinity and Mendocino
counties are projected to receive anywhere from 0.30 to 0.75
inches. Cooler temperatures are forecast during this time frame
and with the passage of the front later this evening, snow levels
will drop to near 4500 to 5000 feet. Accumulating snow will
primarily occur north of HWY 299 and in the Trinity Alps and
Siskiyou Mountains; however, a light dusting to up to 1 inch of
snow accumulation may occur over South Fork Mountain and the Yolla
Bolly. Conditions will also be favorable for convective showers
and perhaps even a few thunderstorms over the ocean tonight. If a
stronger cell were to get going and hold together, coastal
communities north of Cape Mendocino may hear a few rumbles of
thunder.

Low temperatures for tonight will range from the 30s to near 50
with the coldest temperatures occurring in Trinity, eastern Del
Norte, and northeast Mendocino counties. No freeze or frost
products are expected for these areas, but those who have
sensitive plants may want to move them indoors or cover them up.
Especially if they haven`t received killing cold temperatures yet.

.LONG TERM... (Saturday through Friday) Additional rainfall is
expected over the weekend as a warm front sets up over the
region. This will be a result of the trough pushing eastward and
high pressure building over the area. Accumulating rain is
expected to stay north of Mendocino County with Del Norte and
northern Humboldt counties receiving most of the rain. By early
next week drier and warmer weather will return to northwest
California.




&&

.AVIATION...A cold front generating rain across the Pacific
Northwest early this morning will sag southward into far NW California
by midday today. The rain may become briefly heavy this afternoon
and evening resulting in IFR ceilings and reduced vsbys for KCEC.
Winds will be quite brisk both at the surface and aloft. KCEC may
experience gusts to 45 mph. For KACV the strong winds will
probably remain aloft and the potential for low level wind shear
will be present. The rain will likely hold off for KUKI til this
evening or overnight. Conditions will likely deteriorate to MVFR
at KUKI this evening. A trough in the cold and unstable air mass
following the front may produce isolated tstms near the coast
later tonight. Overall, conditions will likely improve to VFR or
MVFR later tonight for the coastal terminals after the front
transitions southeastward.


&&

.MARINE...The tail end of a cold front will move across
the waters today. Southerly winds in advance of this cold front will
briefly gust up to 35 kt north of Cape Mendo by early afternoon.
Steep southerly wind waves will also be generated, primarily outside
10NM and along the western fringes of the inner waters. Large west
to northwest swell from 18 to 22 feet with long periods will build
behind the front tonight. It may take til the mid to late evening
for the swell to arrive and for high surf to develop. High surf will
pound the shoreline on Friday with breakers around 23 to 25 feet
expected. A warm front will generate a new round of brisk southerly
winds and steep southerly waves north of Cape Mendo on Saturday.
Winds will fall below advisory or warning levels on Sunday, however
seas will likely remain elevated through the weekend. Brisk north
winds should return early next week.


&&

.FIRE WEATHER...Increasing southerly winds are forecast for
today and will primarily affect coastal Del Norte county and
ridges above 1000 feet in Del Norte and Humboldt counties. Gusts
up to 40 to 45 mph are expected for these areas, thus a Wind
Advisory has been issued. Elsewhere, winds are expected to be
breezy; however, with improving humidities and rain moving into
the area there should be a minimal fire threat. Look for all of
northwest California to receive a wetting rain with areas north of
Mendocino County receiving the most amount of rain. For areas
where there are active fires, total rainfall amounts should reach
to at least 0.30 inches, especially as you move north of Ukiah.

Additional chances for rain will continue into the weekend, but
should remain confined northern Humboldt and Del Norte counties.
By early next week, high pressure will take hold of the forecast
and bring warming and drying conditions to the area.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory from 5 PM this afternoon to 6 PM PDT Friday
     for CAZ101-103-104-109.

     Wind Advisory from 11 AM this morning to 5 PM PDT this afternoon
     for CAZ101-102-104>106.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 5 PM PDT this afternoon for PZZ470.

     Hazardous Seas Warning from 5 PM this afternoon to 6 PM PDT
     Friday for PZZ450-455-470-475.

     Small Craft Advisory from 9 AM this morning to 5 PM PDT this
     afternoon for PZZ450-455-475.

&&

$$

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