Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 211134
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
334 AM PST Tue Nov 21 2017

.SYNOPSIS...Mainly dry weather and cloudy skies are expected
today with occasional light rain possible this afternoon in the
north. Wednesday and Thursday will continue to see unsettled
weather with cloudy skies and occasional light rain. Friday looks
mainly dry before another system brings rain for the weekend.

&&

.DISCUSSION...The atmospheric river and warm frontal boundary that
brought significant rain to the area yesterday have moved out of
the area. Water vapor satellite continues to shows a plume of
moisture off the coast and a ridge over the west coast. This has
brought a very warm and moist airmass to northwest CA this
morning. Along the coast temperatures are in the upper 50s to
middle 60s, while temperatures inland are somewhat cooler. Breezy
south winds are also impacting the area. Some gusts to 45 mph are
possible over the higher peaks of Del Norte county. These will
diminish slightly in the afternoon.

Mainly dry conditions are expected this morning although clouds
will persist and some light rain or drizzle is possible over the
higher terrain. Currently there is a shortwave well off the coast
riding up the plume of moisture. This afternoon the GFS has this
wave moving up through the southwest flow and pushing the moisture
plume and some precip onshore in Humboldt and Del Norte counties.

Tonight the moisture plume moves back offshore, but clouds and
warm temperatures will persist. Some fog is possible, especially
in Mendocino county if the high clouds clear out a bit.

Wednesday and Thursday the GFS continues to the GFS continues to
show subtle waves in the flow bringing occasional light precip to
the much of the area. Confidence is low on the exact timing and
strength of each of these waves, but due to the moist airmass
precip looks likely at some point.

Friday the ridge builds a bit and most of the area is expected
to see dry weather. There is still a slight chance of rain in the
forecast This is mainly due to the possibility of the systems on
either side of this window speeding up or slowing down. Partial
clearing is possible, but confidence is low on that as well.

Friday night into the weekend another system moves onshore.
Initially a warm front passes through the area Saturday, followed
by a cold front Saturday night and another one on Sunday. The GFS
is colder with this second system than the ECMWF. There is the
potential for snow down to hwy pass levels in Trinity county. MKK

&&

.AVIATION...Prevailing VFR conditions can be expected at most
terminals between 12Z Tuesday and 12Z Wednesday, with a few
exceptions. Low clouds and mist across interior valleys, including
near UKI, may result in periodic LIFR ceilings early in the morning
but should improve shortly after sunrise. Along the coast, brief
MVFR ceilings will be possible during the afternoon and evening
along with some light rain. In addition, coastal terminals will
flirt with LLWS criteria for nearly the entire 24 hour period,
likely maintaining near 30 kt of wind shear between 0 and 2000 ft
AGL with minor fluctuations. /BRC

&&

.MARINE...Southerly to southeasterly winds will continue to increase
across the waters this morning as a warm front lifts to the north of
the area and a cold front slowly approaches from the west. Winds
will peak during the afternoon, reaching near Gale strength across
the waters 10+nm offshore and north of Cape Mendocino. Waters south
of the Cape and closer to shore will remain more sheltered from
these stronger Gales, but will be moderately breezy nonetheless.
These southerlies will result in building steep seas, particularly
in the northern offshore areas with the strongest winds.

Overnight Tuesday, winds will weaken slightly, but will remain fresh
to strong through late Wednesday. Meanwhile, both a fresh southwest
swell and a longer period northwest swell will move through the
waters at this time, and the end result will be a chaotic and
uncomfortable sea state that will last through Wednesday night.
Winds will weaken Thursday and allow the steeper southerly seas to
settle, but the previously mentioned swells will maintain improved
but still somewhat uncomfortable conditions through the end of the
week.

On Saturday, another cold front will bring a return of strong
southerlies, and this will be followed closely by a building long
period northwest swell. /BRC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 5 AM PST early this morning for
     PZZ470.

     Gale Warning from 5 AM early this morning to 4 PM PST this
     afternoon for PZZ470.

     Small Craft Advisory until 4 AM PST Wednesday for PZZ475.

&&

$$

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