Winter Storm Watch 9, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
255 PM PST Fri Mar 8 2024

.SYNOPSIS...Sunny and mild weather comes to an end tonight as the
first of a series of shortwaves impacts the area beginning tonight,
bringing rain, mountain snow, and gusty wind through Tuesday
morning.

&&

.DISCUSSION...Calm and mild weather today will quickly come to an
end, with the first of a series of shortwaves arriving tonight.
Impacts will be minimal with a quick burst of a quarter to a half
inch of rain in Humboldt and Del Norte Counties. Lower amounts are
forecast in Lake, Mendocino, and Trinity counties, with trace to
0.25 inches expected. Snow levels will remain primarily above 4000
ft for this system, giving the highest mountain peaks another 3-5
inches of snow. Wind gusts along the coast will increase, with
southerly gusts up to 40 mph possible in coastal Del Norte, and up
to 30 mph in coastal Humboldt. This system quickly exits the region
Saturday afternoon.

A larger system arrives Sunday morning, bringing another round of
rain and gusty winds. Rain rates of the initial rain band will be
heavy, with HREF members showing a near 50% chance of rain rates of
0.25/hr. This heavy rain will be accompanied with strong SSE wind,
with peaks gusts up to 55 mph in coastal Del Norte, up to 40 mph in
coastal Humboldt and Mendocino, and up to 30 mph in the interior
valleys, including Lake County. Exposed ridges could see gusts in
excess of 60 mph. Rain amounts will be high as well, with areas of
Humboldt and Del Norte counties seeing 1-2 inches of rain, with
higher amounts locally in higher terrain. Trinity, Mendocino, and
Lake Counties are forecast to see 0.5-1 inch of rain, with locally
lower amounts forecast in Lake County. Snow levels will gradually
lower from 4000 ft with this system, except in Trinity county where
snow levels could reach as low as 2000-2500 ft. This will impact
mountain passes along Highways 3, 36, and 299. This system exists
the area by Monday morning.

Another system arrives Monday bringing another round of gusty winds
and widespread rain. NBM currently showing a 40% chance of 1 inch of
rain in coastal Del Norte and Humboldt and around a 20-30% chance in
much of Mendocino and Lake Counties. Snow levels currently look to
be around 3000-3500 ft, bringing more snow to the mountains and the
passes along Highway 3 and 36. Rivers are expected to rise with
this deluge of rain, but are currently forecast to stay below
flood stage. The Eel and Mad Rivers do have a roughly 30% chance
of reaching monitor stage, and this will need to be monitored in
the coming days.

A ridge builds in midweek and into the weekend, bringing warmer
temperatures, potentially into the 60s along the coast and 70s
inland. JDB

&&

.AVIATION...VFR conditions have persisted today with mostly clear skies across
Northwest California. A few coastal clouds have formed in the last
couple of hours along the Del Norte coastline, but so far these have
only brought a few clouds to CEC. As the evening progresses moisture
will increase and cloud cover will gradually increase in kind ahead
of an approaching cold front. Ceilings will rapidly fall to around
high end MVFR overnight into the morning hours, spreading inland and
south from the northwest. A brief period of gusty south winds is
likely in advance of the front along with or just ahead of a thin
band of moderate rain. Winds will veer to the southwest behind the
front and become less gusty around daybreak at ACV and CEC. Winds
will be much less of a factor in the Ukiah area. Showers will then
linger behind the front through the day but will decrease in
coverage significantly by late afternoon. /RPA

&&

.MARINE...Lighter winds will continue to turn southerly throughout
today. However, tranquil conditions won't last long, with a series
of fronts this weekend poised to bring strong winds and hazardous
seas. Southerlies will begin to build in tonight. Winds will be
strongest in the northern waters with gale force gusts in isolated
areas, though gusts in excess of 21 kts are expected in all waters
by tomorrow. After a brief lull, a much stronger front will sweep
across the waters early Sunday. This front will bring gale force
southerly winds, especially in the northern waters, with NBM showing
a 70 to 90 percent chance of at least isolated gusts in excess of 50
kts. An approaching third front will keep at least moderate
southerly winds into next Tuesday.

Steep short period seas will follow the stronger winds with the
steepest waves to 14 feet at 10 seconds. In addition to short period
seas, a series of northwest mid period swells will follow each
front. The steepest swell will build early Monday with the most
likely height of 16 feet at 14 seconds. That said, wave ensemble
models show a 40 to 60% chance of waves at least briefly peaking
over 18 feet. Between short period seas and swells, combined seas in
excess of 10 feet will build across all waters by Saturday afternoon
and continue through much of next week. Such a combined sea state
will generate conditions hazardous to small craft. /JHW /JLW

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Wind Advisory from 10 PM Saturday to 11 AM PST Sunday for
     CAZ101-102.

     Wind Advisory from 1 AM to 11 AM PST Sunday for CAZ104>106.

     Winter Weather Advisory from 10 PM this evening to 4 PM PST
     Saturday for CAZ107.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 9 PM this evening to 9 PM PST
     Saturday for PZZ450-470.

     Gale Watch from Saturday evening through Sunday morning for
     PZZ450-470.

     Small Craft Advisory from 9 PM this evening to 9 AM PST
     Saturday for PZZ475.

&&

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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png