738
FXUS66 KEKA 121228
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
528 AM PDT Wed Mar 12 2025

.SYNOPSIS...A series of storms will bring multiple hazards to
Northwest California through early next week. Strong winds
expected again today with heavy Snow in the mountains. Snow
levels plunging with small hail and low elevation snowfall
creating very slippery road conditions tonight through Thursday.


&&

.DISCUSSION...A series of storm systems will bring multiple
hazards to Northwest California through the weekend. A period of
heavy mountain snow is expected to arrive with a cold front this
morning. Snow levels will initially remain above 3500-4000 feet
before plummeting down to 3000-3500 feet behind the cold front
this afternoon. Snow levels will continue plummet tonight and
Thursday, down to 1500 to 2500 feet with generally lower
accumulations but greater impacts to travel and population centers
and communities. Snow will be possible down to the valleys floors
by early Thursday morning, 500-1500 feet, however accumulations
will most likely be 1" or less. A winter storm warning remains in
effect through this evening for Trinity County. Snow
accumulations are less certain for Trinity as a cold and showery
air mass spread into the area later tonight and Thu. Westerly
upslope flow into the coastal ranges of Del North and Humboldt
should support hefty snow amounts tonight into Thu as a modified
maritime polar air mass spreads into the region. Snow will likely
have travel impacts on highway 299, particularly at Berry Summit
and perhaps Lord- Ellis Summit. Travels on highway 199 at Collier
Tunnel may also be impacted. Forecast storm total amounts are on
the low end for a winter storm warning for interior Del Norte and
northern Humboldt, generally 2 to 6 inches. Impacts may end up
being higher in these travel corridors due to lower frequency of
snow events and heavier motor traffic. For now we converted the
winter storm watch to a winter weather advisory with generally
below winter storm warning snow accumulations.

Another weather phenomenon we see frequently with these maritime
polar outbreaks is small hail. In fact, impacts for motorists may
be much greater considering how rapidly hail accumulates in what
may seem like safe driving conditions. We may end up needing a
winter weather advisory for coastal areas for small hail
accumulations and winter weather advisories for southern/southwest
Humboldt and perhaps northern Mendocino once snow levels fall
below 1500 feet, Thursday morning. Convective allowance models do
show modest CAPE values near the coast. We will need to monitor
the activity for the possibility of stronger storms and perhaps
waterspouts in regions of regions of localized helicity generation
in the lee of Cape Mendocino/around Shelter Cove.

After a brief break Thu evening, another storm and low snow
levels (1500-2500 feet) is forecast to arrive quickly late Thu
night into Friday morning. More winter weather products for
hazardous winter weather conditions will be necessary especially
for the west slopes of Del Norte and Humboldt Counties.

We may see a break in the active and wet weather as a ridge pumps
up over the area, but ensemble clusters indicate a flatter ridge
and wetter scenario. Yet another powerful storm will likely bring
another bout of moderate to heavy rain and mountain snow as well
as strong winds later in the weekend and early next week. There is
still a great deal of variability with the timing and magnitude
of this late weekend/early next week storm and all the fine
details are difficult to resolve multiple days out. Even the best
ensemble guidance may be skewed to wet or too high with winds.
Stay tuned for updates. On a positive note, we may finally have a
longer lasting break in the wet/unsettled weather by mid next
week, but potential for morning frost and subfreezing temperatures
will be on the rise again if skies become clearer. DB

&&

.AVIATION...A passing cold front is creating MVFR/IFR conditions
this morning. Rain and gusty winds at terminals are to be expected
through the morning. Gusty winds will be accompanied by a Low Level
Jet causing Low Level Turbulence at 1500-2000 ft AGL due to
southerly winds at 35-40kts through 18Z. Lingering showers will
be present through the rest of the day bringing possible periods
of IFR conditions to an otherwise MVFR, overcast afternoon.

&&

.MARINE...Southerly wind gusts of 34 to up to 40 kts are forecast in
all zones through this morning, particularly over the northern
waters. Steep, short period seas will build over 10 ft through
Wednesday morning. Conditions will improve throughout the day  as
winds and seas diminish in the wake of the storm. A long period WNW
swell will also build in today, bringing seas back over 10 ft
Wednesday night. Winds will turn westerly this afternoon through
Thursday, and some steep, short westerly seas around 5-6 ft will
propagate into the waters through Thursday, with combined seas of 10
to 12 ft. Southerly winds will quickly strengthen to gale strength
again Thursday night with another strong front. Steep seas up to 12
ft are forecast as a steep westerly swell combines with the short
period southerly wind waves late Thursday and Friday. This weather
pattern will stay active with another possibly stronger storm system
moves through late Saturday with solid gale conditions currently
forecast into Sunday. JJW/DS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Winter Weather Advisory from 5 PM this afternoon to 5 PM
     PDT Thursday for CAZ102-105.

     Wind Advisory until 2 PM PDT this afternoon for CAZ104>106.

     Winter Storm Warning until 8 PM PDT this evening for CAZ107-
     108.

     Wind Advisory until 5 PM PDT this afternoon for CAZ115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Gale Warning until 9 AM PDT this morning for PZZ450-455-470-
     475.

&&

$$

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