441
FXUS66 KEKA 030718
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1218 AM PDT Thu Jul 3 2025

.SYNOPSIS...Cooler interior temperatures and a deeper marine layer
are expected Thursday and Friday. Fire weather concerns today
from gusty afternoon winds and a slight chance for thunderstorms.
Temperatures will then trend warmer through the weekend and into
early next week.


&&

.DISCUSSION...The marine layer has deepened over the last 24 hours,
allowing for a further push inland of a marine-influenced airmass. A
compact and somewhat vigorous shortwave trough will move through the
area from the west Thursday afternoon and evening. This rather
energetic disturbance will bring some limited elevated instability
and moisture aloft. The moderate forcing, steep lapse rates and
strong deep-layer sheer should be enough for thunderstorm
development again over E Trinity County. There is not high
confidence in the coverage that develops inside the Trinity County
boundary, but the CAMS have inconsistently displayed activity over
it.

The trough influence will further deepen the marine layer Thursday
night. This will further expand the marine air inland and also
likely coax out light coastal drizzle in and around Humboldt Bay
and the Eel delta. Temperatures will also be lower around the
coast where the stratus persists. High temperatures will be muted
into the weekend before a building Desert Southwest ridge begins
to trend temperatures higher.

The amount of influence of the building ridge over N CA is still
uncertain. An upper trough will dig south, cutting off from the
flow and becoming closed just off the N CA coast through the
weekend. How it evolves and where it meanders to will determine
the northern extent of the ridge. NBM does not currently show
meaningful probabilities for high temperatures greater than 100F
in the warmer interior valley locations until late next week when
the cutoff low may eject NE. /JJW


&&

.AVIATION...LIFR ceilings are likely or expected along the coast
with a 60-80% chance of LIFR ceilings. Visibility is lower
confidence. KCEC stands a 50% chance of visibility below 3SM at some
point overnight and 50% chance of less than 2SM at ACV. Mean wind
gusts from the northwest for UKI showing just over 20 mph. Better
chance in temporarily eroding stratus at CEC as compared to ACV for
Thursday. ACV holds on to a near 40% chance of LIFR ceilings
throughout the day, with CEC almost certainly scattering temporarily
Thursday afternoon. /MH


&&

.MARINE...Northerly winds will continue in the outer waters with
gale force gusts persisting downwind of Cape Mendocino through late
tonight. Steep and hazardous waves will propagate into the southern
inner waters through Thursday. Moderate to fresh breezes will
continue in the outer waters through Friday as a long period
southwesterly swell fills into the waters, with locally stronger
gusts nearshore and downwind of the Cape. Northerlies expected to
strengthen again late this weekend as high pressure builds back into
the region. NBM currently noting 40 to 50% chance of gale gusts in
the outer waters Sunday through Monday. /MH


&&

.FIRE WEATHER...Gusty winds with low daytime RH`s are forecast for
portions of zone 283 (Trinity County) and zone 264 (southern Lake
County) Thursday afternoon and evening. Wind directions will
generally be from the west and northwest and funneled through the
valleys. Hold over fires from our recent lightning outbreak may
rapidly spread, particularly in Trinity County where lightning
activity was most abundant. These enhanced diurnal winds may
continue on Friday, but are not forecast to be as strong. An
approaching upper trough may also generate some light showers in
NE Trinity County and perhaps isolated thunderstorms (up to 15%
chance) over the highest terrain in NE Trinity. Convective
allowing models have inconstantly trended higher with thunderstorm
coverage, mainly Thursday evening with passage of the trough
axis. Little to no precipitation is expected with these showers
and storms.

Another trough will follow over the weekend and will pose a low risk
for elevated high based and low precipitation producing
thunderstorms over the interior, primarily Trinity County.
Otherwise, temperatures will warm up over the weekend. The warming
will most likely (80% chance) continue all of next week. The
magnitude and rate of the warming remains uncertain, but 100F degree
heat will be possible.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PDT Thursday for PZZ455-470.

     Gale Warning until 3 AM PDT Thursday for PZZ475.

&&

$$

NOTE: The full forecast discussion is now regularly issued between
10 am/pm and 1 pm/am. Additional updates will be issued as needed.

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