023
FXUS66 KEKA 022154
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
254 PM PDT Wed Jul 2 2025

.SYNOPSIS...Cooler interior temperatures and a deeper marine
layer are expected Thursday and Friday. Temperatures will then
trend warmer through the weekend and into early next week.

&&

.DISCUSSION...

Satellite imagery and web cameras showed cumulus clouds building
over NE Trinity this afternoon. Latest CAMS (convective allowing
models) and probabilistic guidance (HREF, SREF and NBM) continue
to trend lower with thunderstorms today over NE Trinity and Yolla
Bolly`s. All of the CAMS indicate activity on the outside
periphery of Trinty and NE Mendo/northern Lake late today. Model
based soundings continue to depict steep lapse rates with
sufficient CAPE for storms. 500mb ridge building in from the SW
and drier westerly flow will most likely cap off storms for our
area today. There is still a 1 in 10 chance for lightning over the
highest terrain in NE Trinity. For coastal areas, stratus has
been slow to clear out and much more extensive than both the NBM
and HREF guidance indicates. Statistical guidance and BUFKIT time-
height humidity sections more closely resembled current cloudy
conditions along most of the coast. A stronger and higher marine
inversion will likely keep cool and humid marine air trapped
against the coastal terrain tonight into Thursday, especially
around Humboldt Bay and Eel delta.

A series of upper trough will move across the area Thursday
through this weekend. The first one on Thursday will have
a strong SW speed max proceeding the trough axis. Isolated
showers are possible (20% or less) over high terrain of NE
Trinity. It is not completely impossible, 1 in 10 chance, for
some cloud-to-ground strikes with trough axis passage Thu evening
over NE Trinity or nearby along the borders. A second short wave
trough will swoop across the area this weekend and should develop
into a semi-closed low over the area bu Sunday. How exactly this
trough evolves remains uncertain. Convective parameters are not
all that high and there is no compelling reason to depart from
the NBM output at this time.

Otherwise, interior temperatures are forecast to trend down Thursday
through Friday in response to gustier westerly and northwest
winds and marine air intruding inland. Temps should warm up over
the weekend and continue on an upward trend early to mid next
week. Coastal areas will most likely continue to have low cloud
cover for the next several days with a deeper marine layer,
hopefully clearing out in afternoon.

&&

.AVIATION...

Deep marine layer continues to blanket the north coast this afternoon.
Greatest chance for MVFR scattering in CEC late this afternoon as
northerly winds increase offshore. Gusts approaching 20 knots
possible at both coastal terminals and UKI beginning prior to 00Z.
HREF shows >80% probability for <1K ft ceilings redeveloping at
ACV after 04Z; CEC seems to be slightly underdone and will likely
return to IFR ceilings overnight. A weak shortwave will disrupt
the wind pattern, bringing scattered high cloud cover and a
greater chance for coastal clearing Thursday afternoon (20-50%
chance of low cloud cover by 22Z Thursday). Gusty northwest winds
20 to 30 knots possible in UKI Thursday afternoon.

&&

.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 inner waters
through Thursday, diminishing first in the northern waters as
winds gradually decrease. 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.

&&

.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. The upper trough may also
generate some light showers in NE Trinity County and perhaps
isolated lightning strikes (a 10% chance) over the highest terrain
in NE Trinity. 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 11 PM PDT this evening for
     PZZ450.

     Hazardous Seas Warning until 11 PM PDT this evening for
     PZZ455.

     Small Craft Advisory until 9 AM PDT Thursday for PZZ470.

     Gale Warning until 11 PM PDT this evening 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