187
FXUS66 KEKA 150705
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1205 AM PDT Tue Sep 15 2026

.KEY MESSAGES...

* Slightly warmer temperatures and northerly breezes are expected
  today.

* A weak frontal system arriving Wednesday will likely lead to
  cooler temperatures and generally unsettled weather with an
  increased chance for thunderstorm development

* Warmer temperatures and dry conditions return end of the week.

&&

.SYNOPSIS...Surface high pressure building offshore will
strengthen the onshore pressure gradient against the interior
thermal low into early this week. Expect a shallow marine layer
pinned along the coast while the interior valleys have dry and
seasonably warm conditions. For Wednesday, an evolving upper low
will bring cooler temperatures and slight chance for interior
thunderstorms.


&&

.DISCUSSION...Warm temperatures remain inland as high pressure and
weak upper level ridging remains over the areas today. This will
result in strong winds for the coast and valleys inland with gusts
up to 20mph possible inland and up to 30mph for the direct
coastline. Any coastal cloud coverage in the morning will likely
dissipate early as daytime mixing and a deepening marine layer
impact the North Coast. Inland valleys could also see morning temps
in the low 40s.

COme Wednesday afternoon, global models have been steady on an upper
level trough ripping down the PacNW coastline before stalling over
Del Norte as well as N. Humboldt and N. Trinity counties. This
trough will create abnormally cooler temperatures inland and
stronger winds for the ridgetops due to the unstable atmosphere.
CAPE values and vorticity signals continue with this system even as
Hi-Res models start to reach out as far as Wed P.M. which increases
the forecast confidence on thunderstorm potential. The Storm
Prediction Center has also included the Northern portions of the CWA
in a thunderstorm potential. Storms will be limited by forcing and
moisture, yet ample life could create a thunderstorm if the
ingredients line up well enough. Storm track currently shows storms
forming inland before potentially flowing westward towards the coast
from the Klamath, Salmon, and Trinity Alp mountains. A small chance
of storms is possible Thursday as a weaker impact from this system
will still be felt. After this system migrates eastward, ridging
returns and will give warmer temperatures for Friday into the
weekend. DS


&&

.AVIATION...VFR and northerly winds are expected to continue for
coastal terminals. Terminals near Humboldt Bay could see MVFR
ceilings develop late tonight with periods of IFR as cloud
development has begun in the Eel River Valley. Any ceilings will
likely give way to VFR by mid morning as northerly winds return.
Inland areas will experience continued afternoon gusts and VFR
conditions.


&&

.MARINE...A fairly strong land-sea surface pressure gradient is
creating strong breezes with near gale force winds through the
overnight hours before building again this afternoon, especially
across the area outer waters. Steep waves are to be expected across
all of the coastal waters through Wednesday morning with waves of 8
to 10 feet. Winds are still expected to diminish slightly through
the afternoon on Wednesday and more significantly Wednesday night as
an upper level trough moves down over the area. Some models do show
these winds diminishing earlier, but confidence is low on the exact
timing. Light southerly winds are expected Thursday as the low moves
through and then out of the area. Northerly winds are expected to
increase on Friday and more so over the weekend. MKK


&&

.FIRE WEATHER...High pressure building off the coast will continue
the warming and drying trend across Northwest California today.
Wednesday afternoon or overnight an upper low entering over Del
Norte, Humboldt, and N. Trinity counties has the potential to cause
a few thunderstorms. There is still a lot of uncertainty on the
details of these storms, yet the most likely scenario seems to be
storm forming over the Salmon, Klamath, and Trinity Alps before
flowing towards the coast. Storm chances remain low overall, yet the
potential area for these storms has increased due to the models
remaining fairly steady with this systems storm track. There will
likely be rain with each of these storms, yet some lightning that
strokes away from the core of the storm could start a fire. It is
possible that the there could be a few storms on Thursday, but these
are expected to be limited to northern Trinity county and Siskiyou
county. Warmer and drier weather along is expected to return Friday
and Saturday. MKK/DS


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 AM PDT Wednesday for PZZ450.

     Small Craft Advisory until 8 PM PDT Wednesday for PZZ455-
     470.

     Small Craft Advisory 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