458
FXUS66 KEKA 250815
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1215 AM PST Tue Nov 25 2025

.SYNOPSIS...Cold overnight temperatures and patchy frost is possible
today and Wednesday. Generally dry weather and warm temperatures
through mid week. There is a chance of light rain and sprinkle Day
for Del Norte and Northern Humboldt counties on Thanksgiving Day,
followed by dry and cooler weather conditions through the weekend.


&&

.DISCUSSION...A dry offshore flow (easterly wind) is expected to
develop across the area into Tuesday, with some breezy conditions
over the higher terrain. Areas of fog and patchy dense fog are
anticipated along the shelter valleys, mainly in Humboldt and
Mendocino counties. Lingering cold air will promote overnight
temperatures to be a few degrees cooler than today`s readings, with
lows in the upper 30s to mid-40s for the coastal areas and generally
in the upper 30s inland. The lowest temperatures are expected for
Trinity County, with temperatures as low as 28 degrees in the
coldest areas like Hayfork and Ruth. A Frost Advisory is in effect
until 9 AM PST this morning for northern Trinity County and Southern
Lake County. A Freeze Warning is also in effect for Southern
Trinity, Northern Lake, and NE Mendocino Counties until 9AM.

Ridging will continue to build and strengthen over the area through
the day into Wednesday, promoting quiet weather conditions with a
drying and warming trend. Dry offshore flow, especially at night,
will scour out some of the low-level clouds near the coast, which
should lead to more afternoon sunshine compared to today. High
temperatures are forecast to range from mid- to upper-50s along
coast and mid-60s inland. Additional warming is expected Wednesday
afternoon, with highs in the upper 60s in the warmest interior
valleys. Any areas that do have fog develop overnight will likely be
slow to clear and may have high temperatures that are lower, leading
to lower than usual forecast confidence.

A subtle shift in the weather pattern is expected for Wednesday
night and Thursday (Thanksgiving Day). High pressure begins to shift
eastward as a shortwave trough and its associated surface low move
toward the PacNW. A weakening cold front crossing the area will
bring light rain and sprinkles for Thanksgiving Day, for Del Norte
and Northern Humboldt counties, with most rainfall totals under a
tenth of an inch. Elsewhere, increasing cloudiness and mostly dry
conditions are expected.

Looking ahead for Friday and through the weekend, the general
consensus between ensemble and deterministic models shows an upper-
level trough dropping southward while an upper level ridge builds in
the Gulf of Alaska. There is, however, high uncertainty in the
position of this upper-level trough, with models showing variable
solutions, especially over the weekend. The ECMWF, GFS ensemble
means and clusters show similar solutions with the upper trough
dropping south over land and becoming positively tilted.
This solution typically leads to dry and colder weather, leading to
additional inland freezing temperatures this weekend. Only ~20% of
the cluster mean are showing widespread precipitation, while the
~80% suggest dry weather conditions.
/ZVS


&&

.AVIATION...High pressure is building in and offshore flow is
keeping the coastal areas clear. Inland valleys are seeing fog
across many of them. Some fog may creep into UKI towards morning,
but confidence is low on this. The fog is expected to take its time
clearing once again across the interior valleys. Tonight fog is
expected to return across the interior valleys. Offshore flow is
expected to be slightly weaker along the coast and it is possible
some stratus will develop by Wednesday morning. MKK


&&

.MARINE...Northerly winds are continuing to diminish this morning as
high pressure moves off to the east of the area. The northwest swell
continues to slowly diminish and is expected to be around 6 to 8
feet by sunrise. The winds driven waves are diminishing as the winds
do. They may drop off more quickly than forecast making for quiet
wind and waves on the water for the remainder of the day. The calm
conditions linger through much of Wednesday as well and the swell
continues to slowly diminish.

Wednesday afternoon these are expected to start becoming southerly
again as a frontal boundary approaches the area. The models continue
to weak the southerly winds and keep the system farther north. Now
it looks like the stronger southerly winds will only around 10 to 15
kt. Thursday afternoon northerly winds return and are expected to
strengthen on Friday. Models are still in fairly good agreement on
this. For the weekend the models have trended towards keeping the
northerly winds in place. Some of the models show these northerly
winds fairly strong at around 30 kt, especially in the southern
waters.

The next swell is expected to build in on Thursday. The most recent
model runs are showing this building to 8 to 12 feet at 15 seconds.
However the GFS and the Global Wave Watch (Waves from GFS winds)
have been seeing some fairly big differences from run to run. So
confidence is lower than normal on these wave heights. MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Frost Advisory until 9 AM PST this morning for CAZ107-115.

     Freeze Warning until 9 AM PST this morning for CAZ108-111-
     114.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 2 AM PST early this morning for
     PZZ455.

     Small Craft Advisory until 5 AM PST early this morning 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