Small Craft Advisory 100, NWS Eureka, CA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
114 PM PDT Wed Sep 24 2025

.SYNOPSIS...Isolated light showers will be possible for southern
Lake and southern Mendocino Counties Wednesday. Otherwise, dry and
stable weather with an increase in coastal fog and stratus is
expected for the rest of this week. Additional troughs may yield
some rain late in the weekend, with increasing chances through early
next week.

&&

.DISCUSSION...A closed low off the coast of Central California is
slowly moving northward today. Some high clouds are starting to
stream into Lake and southern Mendocino counties. Most of the
showers and thunderstorms are likely to remain to the south of the
area, but a few sprinkles aren't out of the question for southern
Lake and Mendocino. Dry lower levels may prevent any rain from
reaching the ground, but if any does, no more than a few hundredths
is expected. Gusty outflow winds of 25 mph or more are possible, if
showers end up arriving into the area.

Elsewhere, stratus is surging northward along the Mendocino coast
and has reached the Humboldt coast late this morning. If not already
there, stratus will arrive by the afternoon and evening and likely
remain overnight as onshore winds remain light.

A weak front will push the upper low back south on Thursday. High
pressure ridging will then attempt to nose back in from the west
Friday. There is growing evidence that NE Pacific troughing will
then suppress the ridge through the weekend. Models handle trough
advancement poorly this time of year. There will not be a strong and
dominant high pressure ridge ahead of it, giving better chances at
stronger weather systems punching in.

An upper-level trough moves through the Pacific Northwest Sunday
into Monday and models are increasingly confident in this dipping
south into our area, with virtually all ensemble members showing
this scenario. This will bring widespread rainfall and gusty
southerly winds to the area. NBM probabilities of a half inch in 24
hours is near or over 50% across NW California. Chances for over an
inch in 24 hours is around 50% for much of the higher terrain in Del
Norte, Humboldt, and Trinity, and 20-30% elsewhere across the area.
Gusty southerly wind is possible with this front. NBM probabilities
for peak gusts over 30 mph are over 50% in the higher terrain and
coastal headlands of Del Norte and Humboldt and channeled terrain in
Trinity. Another frontal system moving through Tuesday is likely to
continue rain impacts and bring another shot of gusty south winds.
Some more uncertainty exists with this front, but still there are
over 30% probabilities for gusts over 30 mph in channeled terrain,
coastal headlands, and ridges. ECMWF 925 mb winds are approaching 70
kts, and if that scenario occurs winds could be stronger, but this
is approaching a week out and can change by then. Stay tuned.
JB/JJW

&&

.AVIATION...(18Z TAFs)...Stratus has moved up the Mendocino coast
and around Cape Mendocino. This as started to impact ACV with LIFR
ceilings and likely will move up the coast toward CEC by this
evening as well. Stratus is likely to become more widespread and
visibilities are likely to lower in the evening and overnight.
Inland areas are likely to remain VFR with generally light winds for
the next 24 hours, though there is a low chance (20%) for UKI to see
stratus early Thursday morning.

&&

.MARINE...Northerly winds continue to move further offshore as
southerlies along the coast fill in overnight through the morning.
Seas are also starting to subside as these winds diminish leaving
decaying wind waves and a mid-to-short NW swell of 5ft@10s. The
aforementioned southerly winds nearshore may be breezy around Cape
Mendocino, and has carried a slug of stratus and fog northward with
it.

High pressure will then noses back from the west in Thursday as a
center of low pressure off the CA central coast moves inland. The
synoptic movement will strengthen the surface pressure gradient
against a cutoff upper low over Central CA and the High pressure
building from the NE Pacific. As a result of this pressure gradient,
northerly winds strengthen Thursday through Friday. Gale conditions
are looking more likely in the outer zones. NBM now holds a 60 to
90% chance for gales late Thursday and Friday. Steep seas are
currently forecast to build to 10-12 ft in the outer waters through
that period, creating conditions hazardous to small crafts in the
inner waters.

&&

.FIRE WEATHER...Above normal high temperatures and low daytime
RH's are expected through Friday and perhaps into the weekend.
Southerlies and upslope breezes generally prevails as we head into
as a cutoff low drifts closer from the south. Potential for
lightning and deep moist convection with this low is looking quite
low (5%) for our southern interior, particularly southern Lake on
the border with Napa and Sonoma. RH's should increase slightly with
the southerlies in some areas near the coast and areas susceptible
to marine air intrusions from the south and eventually the west. A
westerly wind surge will generate gusts over 25 mph in Lake County
this afternoon. Gusty outflow winds, if any, could increase this
further, but confidence is lower. Northerlies ramp up over the
coastal ranges toward the end of the week, Thu-Fri, after a cut-off
low moves back toward south across southern California. Northeast
winds of 20-30 mph are possible in interior Del Norte and the
northeast Humboldt ridges Friday night into Saturday. This will
generally bring RH recoveries down.

Ahead of an approaching front on Sunday evening and overnight, winds
turn southerly and may be gusty. Gusts on exposed ridges and
channeled terrain could exceed 30 mph. This front is also likely to
bring widespread wetting rain, but the winds ahead of the front
could bring a brief fire weather risk.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 3 PM Thursday to 3 PM PDT Friday
     for PZZ450.

     Small Craft Advisory from 3 PM Thursday to 11 PM PDT Friday
     for PZZ455.

     Gale Warning from 11 AM Thursday to 3 AM PDT Saturday for
     PZZ470.

     Gale Warning from 3 PM Thursday to 3 AM PDT Saturday 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