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Area forecast discussion 
National Weather Service Eureka California
311 PM PST Sat Dec 20 2014

Synopsis...widespread rains will continue across the area
tonight...then begin to decrease from the south on Sunday. Some
rainfall may be locally heavy tonight...mainly across the terrain
of del norte and northern Humboldt counties. Building high
pressure will dry the region out early next week.


Discussion...widespread rains continue across much of the area
this afternoon as an atmospheric river remains focused on the or
and north California coast. Heaviest rains have occurred across the
orographically favored locations of del norte and north Humboldt
counties...where over 2 inches of rain have fallen in the past 18
hours or so. 18z blended total precipitation water satellite imagery showed
the highest atmospheric moisture content poised to come ashore north
California and extreme SW or. Models suggest that the deepest moisture
will gradually shift north overnight. As a result...rains may begin to
taper off over portions of Mendocino County. However...rains will
continue elsewhere...and more locally heavy amounts are possible
over del norte and north Humboldt...possibly as much as 1 to 2

On sun...rains will further decrease over the S 1/2 of the
forecast area. Favored locations of del Norte County will still
see categorical rain chances...but rainfall rates should be on the
wane. Still...12z-00z totals may approach 1 inch along SW facing
terrain of del Norte County.

Rains will continue to decrease Sun night and Monday. Skies may
remain mostly cloudy through the day...although partly cloudy skies may
return to the interior S of cape mendo prior to sunset. Reduced
cloud cover...lighter winds...and abundant ground moisture will
lead the way to valley fog Monday night into Tuesday morning.

Another quick shot of rain is prognosticated for Wednesday...but this will
mainly affect areas north of cape mendo...and support for widespread
precipitation will quickly drop Wednesday night. Any lingering precipitation will
likely turn to snow above 5k feet...but amounts are expected to be
light. /Sec

High surf...a high surf advisory remains in effect as a slowly
decaying northwesterly swell causes waves to break near 22 feet
through this evening. Surf heights shall decrease to below advisory
criteria later tonight. Never the less, the decaying swell is still
capable of producing larger sets of waves that can wash over jetties
and rocks this weekend. Beach goers take heed and stay farther back
and never turn your back on the ocean. \Kml

Coastal flooding...prolonged southerly winds in conjunction with
high astronomical tides will bring the potential for minor coastal
flooding through weekend into early next week. Tides have been
running 1 feet above predicted levels and are expected to continue
through the weekend. Another coastal Flood Advisory will need to be
issued for the north coast late Sunday morning as tides are expected
to surpass 9 feet. Areas around Humboldt Bay including the Arcata
Bottoms and King Salmon can expect minor salt water flooding of low
areas around the Bay. \Kml


Aviation...steady rain continues to impact airfields across
northwest California brining MVFR down to IFR. Breezy winds along
the coast will ease into the evening. Expect ceilings and
visibilities to remain obstructed overnight with heavier showers
deteriorating conditions to IFR and potentially LIFR. Improvement
will come very slowly south of Cape Mendocino as rain decreases
Sunday. Otherwise rain will persist north the cape, especially
across del Norte County, which will maintain poor flying conditions
through the day Sunday. \Kml


Marine...the 17z ascat pass late this morning showed fresh to
strong southerly winds across the outer coastal waters with a small
core of gale winds near Point Saint George. Southerly winds will
gradually decrease this afternoon through Sunday morning as a
building ridge of high pressure weakens the pressure gradient across
the coastal waters. This bubble of high pressure will maintain
gentle to moderate winds through the weekend.

As for seas, the significant wave height has been wavering between
17 to 20 feet this afternoon. The northwesterly swell generating these
high seas will subside through the evening thus allowing the sea
state to gradually decrease. The hazardous seas warning has been
extended through 7 PM this evening as the swell has been slower to
subside than what wave models have previously indicated. Once the
warning expires tonight, small craft advisories will persist across
all zones of the coastal waters through early next week to account
for the large but slowly decaying sea sate.

Surface high pressure across the Pacific northwest will maintain a weak
pressure gradient for the early half of next week meaning fresh to
moderate winds. However, a large northwesterly swell will build into
the coastal waters Monday helping to keep an elevated sea state
through the week. Northerly winds will increase Wednesday and
Thursday as a passing trough tightens the pressure gradient. \Kml


Eka watches/warnings/advisories...
California...high surf advisory until 6 PM this evening for caz001-002.

Northwest California coastal waters...
Small Craft Advisory until 3 PM Monday for pzz450-455-470-475.
Hazardous seas warning until 6 PM this evening
for pzz450-455-470-475.



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