815
FXUS66 KEKA 231424 CCA
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
451 AM PST Sun Feb 23 2025

.SYNOPSIS...Steady stream of moisture and rain will shift northward
into SW Oregon this afternoon and evening as a low pressure system
intensifies offshore. Strong south winds are expected for the North
Coast and interior mountains on Monday with cold frontal passage.

&&

.DISCUSSION...Heavy rain has been occurring across Del Norte and
far northern Humboldt Counties through the night. So far amounts
ranged from 1.00-1.50 inches along the Del Norte Coast to 2.00-2.50
in the interior of Del Norte and far northern Humboldt. Hourly rates
have been heavy, around 0.30in/hr in the interior. HREF guidance
continue to indicate these heavy rates decreasing later today as the
IVT moisture plume shifts northward. In fact, the HREF continues to
depict precip falling off considerably for much of the area mid to
late morning through this afternoon. The exception will be across
Del Norte/far northern Humboldt where moderate (0.20in/hr) to
locally heavy rain rates spike up again in afternoon. We still
cannot rule out run-off impacts and the potential for mud/landslides
or rock falls in the steep terrain along 199 and perhaps 101 north
of Klamath. A flood watch remains in effect. We will continue to
highlight this threat in a weather story graphic and social media
post. The potential for heavy rain is forecast to drastically
diminish per all the deterministic models tonight as a surface low
spins up just outside 135W north of 40N.

This surface low will intensity and deepen Monday morning. Not
quite a cyclone "bomb" with rapid deepening, but sufficiently
deep to raise concerns for the possibility of damaging winds. The
surface cyclone is forecast by all the models to rapidly progress
NE outside 130W by mid to late morning Monday. Model guidance
continues to keep the strongest and most destructive wind gusts
with this cyclone well offshore and just north of the forecast
area, along the Oregon coast. Surface pressure gradients will be
sufficiently tight to warrant a wind advisory for coastal Del Norte.
We are confident with advisory level gusts to 50 mph. Now, the ECMWF
ensemble continues to indicate ensemble mean wind gusts near 55 mph
for Pt St George and KCEC airport. In fact there are 49 out 102
members (including the control runs) that indicate gusts of 55 mph
or more (49% chance) from 4 AM to 4 PM MON. Gusts to 60 mph or more
is not completely out of the question for the Del Norte coast and a
high wind watch is in effect.

A wind advisory for the Humboldt coast and Humboldt bay/Eel delta is
much more marginal with gust generally under 40 mph on Monday. We
erred on the side of caution here, especially as a 60kt 925mb speed
max intersects the coastal terrain in advance of a surface boundary.
The stability does decrease and these strong winds may mix down to
mean sea level.

Now looking at the NBM 90th percentile max gusts, it is nearly a
sure thing for gusts to 55 to 65 mph over the interior mountains
of Del Norte. Also, there is high confidence in gusts to 45-55
mph for the Humboldt interior mountains; specifically Kneeland and
Berry Summit.

Strong wind gusts 40 mph or more will make driving difficult and
could knock down tree branches. We will continue to message the
potential for strong and damaging winds in a weather story graphic
and social media post.

Precip will end on Tuesday as broad upper ridging quickly springs
back and holds into mid week (Wed). A shortwave trough will
approach on Thu and will most likely split with the cold core
aloft heading south of the forecast area. Subtropical moisture
influx with this trough is not present and any showers are not a
major concern at this time. There is higher probability for it to be
dry with only a 20-30% chance for measurable precip. Ridging will
build back behind this trough on Fri for the return of dry weather.
Next shortwave trough is expected to advance across the area next
weekend. This trough will probably split too, but does look colder
aloft with more moisture influx for greater amounts of rain and
mountain snow. Overall not a very exciting or eventful progressive
flow pattern as we head into the first few days of March. Granted
the potential for interior convection or tstms will be present with
each of these troughs. DB

&&

.AVIATION...A system moving across the area is bringing gusty
south winds and rain to the coastal terminals. CEC is seeing
stronger wind gusts, which may increase after sunrise to 30 kts or
higher; while ACV may see gusts of 20-25 kts. CEC is also seeing
heavier rain and could see LIFR/IFR ceilings and visibilities
during periods of heavy rain. ACV is seeing lighter rain, and are
likely to see MVFR ceilings. The LLWS threat is significant at the
coastal terminals, especially at CEC where winds could exceed 45
kts between 1500 and 2000 ft AGL. Rain turns more showery this
afternoon and evening, which could raise ceilings to MVFR at CEC
and VFR at ACV between showers. Gusty wind and LLWS return again
tonight into Monday morning as a stronger front moves through.
Impacts to UKI will be minor and conditions are expected to remain
VFR with mainly mid and high clouds and light winds. JB

&&

.MARINE...Strong southerly winds have eased slightly early this
morning, but do still remain elevated around 20-30 kts north of Cape
Mendocino. Near-gale to gale force gusts remain possible in the
northern outer waters today. Seas are characterized by steep
southerly wind waves and a decaying westerly swell. A slight lull
tonight will be short lived as stronger front arrives early Monday.
Strong gale force winds up to 45 kts are possible in the outer
waters, with 35-40 kts possible nearshore. Steep to hazardous seas
will be associated with these winds. Winds ease significantly behind
the front late Monday into Tuesday, but a large long-period swell of
18-22 ft is forecast to fill in behind the front. Seas gradually
lower Tuesday and could dip below 10 ft by Wednesday. JB

&&

.BEACH HAZARDS...A large westerly swell of 22-24 ft at 15 seconds
will fill in late Monday into Tuesday. Breaker waves of 20-24 ft
are possible on west-facing beaches. Confidence is higher for high
surf conditions on the Del Norte and Humboldt coast, but the Mendocino
coast could still see elevated surf of 18-20 ft. Be cautious visiting
area beaches and jetties Monday evening through Tuesday morning
and remember to never turn your back on the ocean! JB

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Flood Watch through this evening for CAZ101-102.

     High Wind Watch from Monday morning through Monday
     afternoon for CAZ101.

     High Surf Advisory from 4 PM Monday to 10 AM PST Tuesday
     for CAZ101-103-104.

     Wind Advisory until 7 AM PST this morning for CAZ102-
     104>106.

     Wind Advisory from 6 AM to 4 PM PST Monday for CAZ102-
     104>106.

     Wind Advisory from 6 AM to 3 PM PST Monday for CAZ103.

     Flood Watch until noon PST today for CAZ105.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 6 AM PST Monday for PZZ450.

     Gale Warning from 6 AM to 3 PM PST Monday for PZZ450.

     Gale Warning until 3 PM PST this afternoon for PZZ470.

     Gale Warning from 3 AM to 3 PM PST Monday for PZZ470.

     Small Craft Advisory until 3 AM PST Tuesday for PZZ475.

&&

$$

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