777
FXUS66 KEKA 201123
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
423 AM PDT Sun Apr 20 2025

.SYNOPSIS...Interior high temperatures are forecast to remain
slightly above average through Tuesday of next week. Overnight
minimum temperatures will remain chilly in some of the colder
valleys, especially in Trinity County. Strong northerly winds over
the coastal waters will keep coastal areas much cooler and
occasionally windy through next week Tuesday.


&&

.DISCUSSION...Nighttime satellite imagery is showing stratus coverage
along the coast and pushing well inland through the valleys.
Coverage has stopped short of Kneeland, but is getting close. The
profiler suggests the depth is just over 2000 ft. Northerly winds
will be slightly stronger than what occurred Saturday, and this will
clear out the stratus. A quick return is expected for around
Humboldt bay this evening as winds ease.

Overnight temperatures in some of the interior valleys are turning
chillier. A drier airmass will move in behind a shortwave trough
that will clip N CA this afternoon. Surface dewpoints will drop into
the low 30s for Trinity County by early Monday morning, and
temperatures are forecast to drop in the the mid 30s in the
valleys, to some isolated low 30s around Hayfork.

Convective allowing models as well as coarse deterministic global
spectral models keep precip and convection to the east of the
area as the shortwave passes. A deeper trough will dig down from
the NW by mid week (Wed). Ensemble clusters continue to show a
great deal for variability with this trough and once again will
not adjust NBM precip chances. A few cluster indicate a wetter
scenario which may amount to a few showers over the mountains.

Latest ensemble cluster means were in generally good agreement with
a trough complex approaching NW CAL by end of day 5 (4/24 Thursday)
with eastward progression across our forecast area through day 8
(4/27 Sunday). Finer details are lacking this far out. Details such
as timing and speed of progression, positioning of the cold core
aloft and just the overall evolution of the trough are still up
in the air and uncertain. It is possible for the upper trough or
cold core low to become negatively tilted which will promote more
t-storm development out toward the coast and over the waters.
Southerly surface winds would make this even a better setup for
storms. Now, multiple individual cluster means are considerably
wetter on days 6 and 7 (4/25 Fri->4/26 Sat) vs the grand 100
member ensemble mean. There is also about an equal membership that
are drier too. NBM continues to indicate 30-50% chance for > 0.25in
of precip in 24 hours. Stay tuned. DB/JJW


&&

.AVIATION...Despite strong northerly wind offshore, winds calming
near shore has allowed for an expansive but elevated marine layer
to form overnight with MVFR conditions at coastal terminals.
Southerly wind has also gradually allowed for low level clouds to
creep up the Russian River Valley bringing IFR conditions again to
UKI. Similar to yesterday, building north wind along shore will
most likely help mix out stratus by late morning allowing VFR
conditions to prevail. Assuming north winds calm, a marine layer
remains likely Saturday night. More exposed terminals like CEC
have a lower chance (30%) of MVFR to IFR ceilings, while chances
are greater around Humboldt Bay (60%). Any clouds that do form
will most likely be later in the evening as North wind is likely
to hold on for at least a bit longer into the evening compared to
Saturday. /JHW

&&

.MARINE...Strong gale force gusts have built in across the outer
waters with gusts in excess of 35 kts. Steep short period seas have
built in response with peak significant waves heights over 12 feet.
Winds have moderated overnight across the inner waters though short
period seas from wind offshore have still maintained a steep sea
state close to shore.

Gales will continue through the day day today in the outer waters.
Stronger near gale force winds and steeper sea will push closer to
shore in the afternoon and evening as the diurnal sea breeze turns
wind more onshore. Gale conditions and steep seas will persist
through around mid week with a daily ebb and flow of winds in the
inner waters. An upper level disturbance later in the week will
finally disrupt and weaken the consistent northerlies around
Thursday. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory from 2 AM to 9 AM PDT Monday for CAZ107-108.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Wednesday for PZZ450-
     455.

     Gale Warning until 3 AM PDT Wednesday for PZZ470-475.

&&

$$

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