471
FXUS66 KEKA 182134
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
234 PM PDT Fri Apr 18 2025

.SYNOPSIS...A warmup to slightly above average temperatures will
continue this weekend into early next week in the interior. Strong
northerly winds over the coastal waters this weekend will likely
persist into early next week. These robust northerly breezes will
keep coastal areas cool and windy at times in afternoons.

&&

.DISCUSSION...Visible satellite imagery showed stratus and fog lingering
near the coastline this afternoon. The fog and low clouds were most
extensive south of Cape Mendocino with web cameras showing a much
more subdued and smashed down marine layer compared to yesterday.
Adiabatic warming will most likely keep the layer compressed and
shallow tonight with less inland intrusion. A sheared-out 500mb
trough and surface frontal boundary will likely bring a new push
of shallow moisture and low clouds to the North Coast late tonight
into Saturday morning. With northerlies increasing offshore and a
shallow influx of marine air a few spats of drizzle will be possible.

Northerly winds will ramp up behind the first shortwave trough on
Saturday with the strongest wind gusts mostly across Del Norte county
coastal headlands. Additional shortwave troughs in the westerlies
aloft will follow Sun-Mon and will serve to reinforce the blustery
and windy coastal northerlies. Confidence northerlies will break
down the persistent stratus locked-in south of Cape Mendocino and
offshore the Mendocino coast remains low. Models have not been
handling small scale eddies spinning up each day. Strong surface
high pressure will remain nearly stationary just outside 140W and
north of 40N into early next week and windy diurnal coastal northerlies
are probable each day. The one exception will be the Mendocino
coast where eddy circulations and stratus may persist each day.

Precipitation chances remain low to non-existent through mid next
week as series of troughs in westerly flow traverse across the
area. 24-hour ensemble cluster means show a potential for a
somewhat wetter scenario Tue-Wed. All this may end up amounting
to is a few showers over the mountains. Not really confident in
any significant precipitation the next 5 days, so will stay with
the NBM guidance at this point. A cooling trend of high temps and
a deeper marine layer with more cloud cover should commence around
mid week and may continue into the latter portion of next week.

Weather could get much more active and anomalous toward the latter
portion of next week and next weekend (Fri 4/25 to Sat 4/26) as a
deep 500mb cold core moves toward or across the NW Cal. There are
multiple possible outcomes. One extreme is a cut-off low may form
well offshore or the 500mb cold core may head south leaving NW
California high and dry with no rain or mountain snow. Another
possible outcome is one that will feature bouts of rain, high
mountain snow and perhaps isolated thunderstorms. A mix or blend
of both of these is also possible. Now, latest NBM indicates a
30-50% chance for 0.25in to 0.50in of rain in 24 hours for Del
Norte/Humboldt and a 10-30% chance elsewhere Thu-Sat next week.
There is even a chance for snow in the high mountains, above 5000
feet. Though amounts do not appear to be very impactful compared
to winter standards. If this wetter and colder scenario pans out,
it will get quite chilly in the high mountains with subfreezing
low temps and near freezing high temps. DB

&&

.AVIATION...Coastal fog has been creating TEMPO periods along
coastal terminals. LIFR conditions due to low level stratus consists
of ceilings of VV002 and Visibilities between 1-3SM. However,
minimal high clouds are keeping terminals in VFR when the fog is not
present. Winds are light today, under 10kts from the north. Tonight
around 0900Z , HREF model data shows over a 70% chance of coastal
fog in and around humboldt Bay and at KACV. Fog is forecasted to
remain through most of tomorrow. Inland at KUKI, morning fog has
burned off and clear skies are forecast through the day. LAMP data
shows a 40% chance of LIFR ceilings (<500ft) returning late tonight
into tomorrow morning around 09-12Z. DS

&&

.MARINE...Calmer conditions will persist today with Fresh breezes
staying isolated to the far outer waters.

A passing upper level shortwave this weekend will once again push
strong northerlies closer to shore. Gale force gusts up to 35 kts
are most likely (~85% probability) in the outer waters with gusts up
to 25 kts pushing into the inner waters each afternoon. Some HiRes
guidance (CANSAC model) shows stronger winds (sustained ~30kts), yet
forecast confidence on winds of this strength manifesting in the
inner waters remains low. Winds build steep short period wind waves
once again in excess of 12 feet. Consistent, strong north wind is
most likely to continue through most of next week. /JHW/DS

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 9 PM this evening to 9 AM PDT
     Monday for PZZ450.

     Small Craft Advisory from 3 PM Saturday to 9 AM PDT Monday
     for PZZ455.

     Small Craft Advisory until 9 AM PDT Saturday for PZZ470.

     Gale Warning from 9 AM Saturday to 9 AM PDT Monday for
     PZZ470.

     Small Craft Advisory until 3 AM PDT Sunday for PZZ475.

     Gale Watch from late Saturday night through Monday morning
     for PZZ475.

&&

$$

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