Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 272323
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
323 PM PST Tue Feb 27 2024

.SYNOPSIS...Strong southwest wind and moderate rain will build along
the coast Wednesday night into Thursday. A strong cold front will
drop snow levels Thursday into the weekend, brining heavy snow to
highway passes across the area through Saturday.


&&

.DISCUSSION...Cool and calm weather will continue through at least
early Wednesday. Winds will turn southerly by Wednesday evening as a
deep trough approaches the area. There is high ensemble confidence
that a very deep trough and associated strong storm system will
approach the coast Thursday through the weekend. As air cools aloft,
high pressure centered over the central Pacific will pull a
continual stream of moisture over the area.

Strong south westerly wind and rain will start late wednesday night
through Thursday morning. Strong southerly wind will be preceded by
the rain. Wind will be strongest at the high elevations of Humboldt
and Del Norte Counties. NBM is showing 70 to 90% chance of gusts in
excess of 60 mph at high terrain in Humboldt and Del Note. Thanks to
high surface stability, there is only a 10 to 20% chance of such
speeds around Humboldt Bay, but there remains a 40 to 60% chance of
such gusts in Crescent City. Regardless, such speeds are possible
very briefly as the front itself crosses the area Thursday
morning.The front will reach the southern half of the area early
Thursday afternoon, generating enhanced wind gusts of 40 to 50 mph
around Clear Lake and in Northern Mendocino County.

NBM shows most likely rainfall of 2 to 5 inches at higher elevations
in Humboldt and Del Norte with 1 to 2 inches elsewhere. Before
precipitation transitions to snow, such amounts do hold the
potential for minor flooding in Del Norte and coastal Humboldt. Warm
air advection with the wind will keep snow levels initially above
5000 ft but cold air building in aloft will quickly drop snow levels
closer to 2000 feet by Friday morning. Mixing along the frontal
passage could sporadically lower snow levels below 2000 feet even
during the day Wednesday, especially in the Humboldt interior. Heavy
snow in excess of 6 to 12 inches should be expected on high highway
passes by early Thursday morning including highways 3, 199, 299, and
36.

Weaker though persistent moisture advection will continue Friday
into Saturday as the trough aloft digs deeper across the area.
Southwest winds will weaken though gusts 30 to 40 mph remain most
likely in areas exposed to the southwest. With the help of dynamic
mixing and upslope cooling, snow levels of 500 to 1000 feet are most
likely in Trinity, Del Norte, and Humboldt early Saturday morning.
Even south in Mendocino and Lake snow levels of 1000 to 1500 feet
are most likely. Though moisture flux will be weakening, most likely
snowfall forecasts Friday - Saturday still show multiple feet at
high elevation locations like Collier Tunnel and Berry Summit. 4 to
12 inches is most likely on the high pass of 101 near Prairie Creek
and in Northern Mendocino County. NBM shows a 50 to 70% chance of
accumulating snow as low as Clearlake in Lake County and Blue Lake
in Humboldt County early Saturday morning. Light snow accumulation
of 1 to 2 inches is most likely at such elevations, though even as
far south as Cobb 4 to 8 inches is most likely at higher elevations.
Even light snow combined with moderate wind could contribute to
widespread impacts and power outages below 2000 feet. Even if snow
doesn`t fall that low, very low freezing levels combined with low
level instability Friday into Saturday hold the potential for
dangerous and widespread accumulating small hail mostly along the
Humboldt and Del Norte Coast. /JHW


&&

.AVIATION...Benign weather today and VFR skies across all the main TAF
sites, resulted in favorable flying conditions. However overnight,
increasing clouds will move into the region, and then around mid-
late morning the far northern coast will experience increasing winds
and lowering clouds as a significant storm system, heading toward
the region, begin to slowly become impactful on Wednesday. Light
rain will most likely move across parts of Del Norte by mid
afternoon. Around the same time, increased "above ground winds" will
become the catalyst for the start of low level wind shear (LLWS)
/TAA


&&

.MARINE...Northerly winds have eased in the northern waters but
remain stout in the southern waters with gusts in the 30 to 35 kt
range. The NW swell continues around 10 to 12 ft at 13 seconds and
will diminish overnight into Wednesday morning. Gale force gusts
peaking at 45 kts in the northern waters, are expected Thursday
morning out of the SSW and will diminish by Thursday afternoon. The
sea state will remain hazardous after the Gale conditions ease,
which will continue into the weekend as a series of cold fronts
approach. A large WNW swell is due to fill into all area waters
later in the week with combined wave heights in excess of 20 ft,
which will last into the weekend.
/EYS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     High Wind Warning from 10 PM Wednesday to 10 AM PST
     Thursday for CAZ101-102.

     Winter Storm Warning from 4 AM Thursday to 10 AM PST Friday
     for CAZ102.

     Winter Storm Watch from Friday morning through late
     Saturday night for CAZ102-104>108-110-111-114.

     Wind Advisory from 1 AM to 10 AM PST Thursday for CAZ103.

     High Wind Warning from 1 AM to 10 AM PST Thursday for
     CAZ104>106.

     Winter Storm Warning from 10 AM Thursday to 10 AM PST
     Friday for CAZ105-106.

     Winter Storm Warning from 10 PM Wednesday to 10 AM PST
     Friday for CAZ107-108.

     Wind Advisory from 4 AM to 4 PM PST Thursday for CAZ110-111-
     114.

     Winter Storm Warning from 4 PM Thursday to 10 AM PST Friday
     for CAZ111-114.

     Winter Storm Watch from Friday evening through late
     Saturday night for CAZ113-115.

     Wind Advisory from 10 AM to 7 PM PST Thursday for CAZ115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Gale Warning from 9 PM Wednesday to 9 AM PST Thursday for
     PZZ450-470.

     Small Craft Advisory until 6 AM PST Wednesday for PZZ455-
     475.

     Gale Warning from 2 AM to 9 AM PST Thursday for PZZ455-475.

     Small Craft Advisory until 6 PM PST this evening for PZZ470.

&&

$$

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