Orick, California Weather Forecast Discussion

845
FXUS66 KEKA 180741
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1241 AM PDT Thu Sep 18 2025
.SYNOPSIS...Inland tempertures will cooldown Thursday with the
arrival of cloudcover and precipitation. Thunderstorm activity is
expected Thursday through Saturday. After a short period of drying,
rain chances increase again early next week.
&&
Key Points:
-Tropical moisture surges in from the south.
-Any thunderstorms that form Thursday would be on the drier side,
capable of strong downdraft winds, and would create a fire weather
threat.
-As moisture becomes better established Friday, the fire weather
threat will ease while an isolated hydrological threat may develop
with thunderstorm activity.
.DISCUSSION...Stratus is following northerly flow and filling
in overnight into early Thursday morning. Coastal intrusion has
only been limited by terrain as the GOES-18 night fog product
shows aggressive advection inland. This will be compounded by
moisture deposited from light drizzle Wednesday evening and a lack
of cloud cover, allowing long wave radiational cooling to take
place resulting in ground fog. Optical depth of the stratus is
becoming dense near the Del Norte coast down to Klamath and north
of Orick, as of 07z. Attention to developing conditions will be
necessary if conditions overnight into Thursday morning worsen, a
dense fog advisory may need to be hoisted if so.
The remnants of a tropical system streams moisture and cloudcover
from the south. Chances for showers increase from the south to north
early Thursday. The amount of instability for the initial moisture
surge is still in question. There is also a good amount of
convective inhibition (CIN) showing up in the soundings. Isolated
thunderstorms may still develop (10%) over the southern regions
through Lake and Mendocino counties starting Thursday. There will be
an initial fire weather threat Thursday with much evaporation of
precipitation likely through the drier lower levels. This will
create gusty and erratic outflow winds around the convective
showers, and particularly with thunderstorms where winds would have
the potential to gust over 40 mph.
The shower and thunderstorm activity will spread northward late
Thursday and Friday. A surface low will form off the coast through
this period, increasing forcing and drawing the precipitation
activity westward through the coastal regions. Models continue to
become more aggressive with this westward push, and precipitation
chances have been increased over the coast. A stray thunderstorm
cannot be ruled out along the coast as well. Instability is greatly
in question Friday as the significant cloud shield and ongoing
showers/light rain will inhibit daytime heating. If Trinity County
and parts of the surrounding counties get a good window of sunshine,
there will be a greater chance for thunderstorms, but that aspect of
the forecast has the greatest uncertainty in general.
This tropically sourced moisture will yield anomalous precipital
water values of 1 inch up to 1.4 inches. Storm motion will be
moderate to slow at times. After the column saturates late Thursday
and Friday, the convective showers and thunderstorms will be capable
of localized heavy rainfall and possible hydrological concerns such
as mudslides. Models begin pulling the moisture out Saturday, easing
the hydrological threat. Saturday does appear to have a good chance
for diurnal clearing and surface heating, and this may bring the
greatest coverage and probability (20+%) for interior thunderstorms
for mainly Trinity County. /JJW /EYS
&&
.AVIATION...(06zTAFs)...A north wind surge will continue to
replenish the supply of cool damp marine air trapped underneath a
stout inversion and the coastal terrain. LIFR conditions blanket the
coast, affecting coastal terminals into Thursday morning. Inland
areas can expect VFR conditions through the TAF period except for
low cloud intrusion into the North Coast river valleys. Mid and high
level moisture from the remnants of a tropical disturbance will
begin to invade skies from the south on Thursday. Convection and
high based t-storms will be possible with the daytime heating over
the interior terrain on Thursday.
&&
.MARINE...High pressure offshore interacting with the low pressure
inland will drastically enhance the pressure gradient creating
strong, gale force sustained winds with gusts over 45kts possible
over the outer waters through Thursday night. Wind waves of 15ft or
more are probable across the northern waters and southern outer
waters.
Marine hazard products have been issued for all marine forecast
zones. Gale Warnings have been issued for the outer waters. Inner
water zones out 10nm can expect near gale gusts with large wind
waves propagating into the waters. Outer water zones 10-60nm can be
subject to gale force winds south of Cape Blanco and Cape Mendocino
and large, very steep, wind waves with blowing spray.
Winds begin to ease slightly late Thursday night through Friday
morning with wind waves beginning to ease Friday afternoon through
Saturday morning. This weekend, a NW swell of 5ft around 12 seconds
is expected with winds between 10-20kts across all the waters.
Global deterministic models are not aligned as to what the synoptic
set up will be, yet cluster analysis indicates relatively zonal flow
aloft with a cutoff low off the coast of Central CA. This will keep
winds breezy, wind waves mild, and the NW swell decaying.
&&
.FIRE WEATHER...Northeast winds will be breezy over the
interior ridges of Del Norte zone 203. These winds will persist into
Friday morning. A remnant tropical system is pushing moisture in
from the south. Showers will move in Thursday with a slight chance
for thunderstorms (10-15%) for mainly Mendocino, Lake and southern
Trinity counties through Thursday afternoon. These initial storms
would be more dry in nature, but confidence is low on available
instability at that time. Convective showers and thunderstorms will
be capable of gusty and erratic winds, particularly in any
thunderstorm development. Moisture and instability increase late
Thursday and Friday when better confidence for isolated
thunderstorms (15-20%) and a potential (45%) wetting rainfall from
showers and more rain productive thunderstorms. Thunderstorm
formation Friday will be somewhat dependent on how much clearing can
occur through the afternoon. Saturday will have a good chance for
diurnal clearing and surface heating, and this may bring the
greatest coverage and probability (20%) for interior thunderstorms
for mainly Trinity County.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 7 AM PDT this morning for PZZ450.
Hazardous Seas Warning from 7 AM this morning to 11 PM PDT
     this evening for PZZ450.
Small Craft Advisory until 11 AM PDT this morning for
     PZZ455.
Gale Warning until 3 AM PDT Friday for PZZ470.
Gale Warning until 3 PM PDT this afternoon 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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https://www.weather.gov/images/eka/zonemap.png

NWS EKA Office Area Forecast Discussion