202
FXUS66 KEKA 132134
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
234 PM PDT Wed Aug 13 2025

.SYNOPSIS...Warm weather will continue to rapidly decline as gusty
northwest winds help pull in cooler marine air Thursday and Friday.
Cool weather will continue this weekend with midlevel clouds and
possibly even wetting rain for the northern half of the area.


&&

.DISCUSSION...High pressure has more rapidly broken down
today with interior highs running a solid 5 to 10 degrees cooler
than yesterday and no locations set to reach highs over 100. A thin
marine layer has again blanketed the coast for most of the day but
has generally cleared by early afternoon. That said, marine clouds
will again quickly rebound again overnight. A shortwave continuing
to form along shore will again allow for periods of overnight
drizzle and marine influence gradually extending further inland

Around Friday, a proper, deep wave trough will sweep across the
Pacific Northwest and help deepen and lift marine influence inland.
Highs will bottom out this weekend in the low 90s for the interior
alongside significant high and midlevel clouds. Gusty northwest winds
will accompany a diffuse surface cold front as the cooler air sweeps
inland as soon as Thursday afternoon but especially on Friday. Gusts
on exposed ridges and in channeled valleys could easily reach 30 mph
or more each afternoon, especially in Lake and Mendocino Counties
where there is even a 10 to 20% chance of isolated gusts over 40 mph
along high terrain.

The highest uncertainty in the forecast has to do with the
potential for precipitation this weekend. There is high confidence
that a plume of moisture reminiscent of an atmospheric river will
accompany the deep trough (precipitable water 1 to 1.5 inches), but
there is much less certainty regarding either instability of lift
sufficient to produce rain. currently, there is a wide range in the
forecast. The greatest chance of rain would be along the coast north
of Humboldt Bay and due to showers over high terrain in trinity
County. About 70% of models show at least a trace of rain in
Crescent City on Saturday with nearly 40% showing even wetting rain.
Those chances fall rapidly further south in Eureka. Rain in the
interior would likely fall in showers over high terrain, some of
which could become isolated thunderstorms (15% or less).
Thunderstorms would be fairly wet with about a 30% chance wetting
rain across interior Trinity County. There is little to no potential
for wetting rain for the southern half of the area. /JHW


&&

.AVIATION...Ceilings at ACV and CEC showing some
improvement this early afternoon with some movement to IFR heights,
but levels still mostly favor 400 to 600 ft AGL levels through
daylight hours. The inversion is holding its strong grip on the
stratus but is showing some signs of fatigue.

The marine layer is observed to have further deepened, and this will
allow for a farther push eastward of the stratus tonight, with LIFR
conditions likely to Kneeland Airport.

High probability (70%) for a return to solid LIFR ceilings 200 to
400ft AGL tonight through Thursday morning for ACV and CEC and
southward through Shelter Cove. Soundings show a similar inversion
height around ACV but a slightly shallower level farther north at
CEC. As with the previous 24 hours, duration of fog looks limited
to TEMPO criteria, with highest chances from 11-15Z (30%). Chances
are slightly higher at CEC through this period (40%).

The stratus may a solid push up the Russian River Valley toward UKI.
Models hint at another such run tonight, but confidence remains
below thresholds for TAF inclusion. Some wind gusts from the south
are forecast this afternoon.

There is higher confidence for the inversion to greatly weaken
Thursday and contribute to better clearing throughout the day.
Clearing is forecast to quickly occur south of the cape around
Shelter Cove overnight by 9Z, but may not fully occur elsewhere
along the coast beyond 18Z.

Winds remain relatively light through this period. A southerly wind
reversal will bring some south gusts along the Far North Coast to
CEC tonight. Northerly will increase across the region on Thursday,
becoming breezy in the afternoon.


&&

.MARINE...Northerly winds increase today mainly over the out marine
zones. Seas are 5-7 feet from long period southerly swells and a
short period northwest swell. The south swell period will mostly be
at 15 seconds today. Northerly winds will continue to strengthen
Thursday at 20-25 kts with isolated 30 kts and gale strength gusts
around Cape Mendocino. Short period seas are forecast to build up to
9 feet over the outer waters Wednesday evening through Thursday
night. Winds and seas will ease Friday, likely remaining low through
the weekend. JJW


&&

.FIRE WEATHER...Hot and dry weather has begun to rapidly pull back,
though fire danger indices remain very elevated as fuels lag.
Moderately elevated conditions will persist over the next couple
days with highs dropping back into the 90s and and RH back around 25
percent. RH recoveries, however, will especially improve with
recoveries generally over 0 percent, especially at lower elevations.
Strong northwest winds will build in during the afternoons Thursday
and Friday ahead of a onshore marine push. Gusts in excess of 30 mph
are most likely on ridges exposed to the northwest and in channeled
valleys, especially along the Russian River and around Clear Lake.
Cooler and more moist conditions will persist into this weekend with
potential for light wetting rain along the north coast (40% chance)
and wet showers and thunderstorms in Trinity County (30% chance).
/JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 AM Thursday to 8 PM PDT Friday
     for PZZ455.

     Small Craft Advisory until 9 PM PDT Thursday for PZZ470.

     Small Craft Advisory from 8 PM this evening to 8 PM PDT
     Friday 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