097
FXUS66 KEKA 132141
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
241 PM PDT Thu Aug 13 2026

.KEY MESSAGES...

* Cooler temperatures are likely late week into the weekend.

* Smokey conditions likely from the MP18 Fire, focused in the
  Trinity River Valley and Trinity County.

* Slight chance of interior thunderstorms today into Saturday.


&&

.SYNOPSIS...Interior temperatures trend below normal to end the
work week. Coastal areas continue to have overnight stratus
with afternoon clearing chances and breezy northwest winds. There
is a slight chance for dry thunderstorms each afternoon from today
and into Saturday for the interior.


&&

.DISCUSSION...Smoke from the MP 18 fire continues to impact air
quality over Northern California, particularly in the interior
valleys of Humboldt and Trinity counties. Depending on fire
containment, expect a similar pattern to carry on. The low level
inversion is showing signs of weakening as a synoptic trough
pattern passes through. This feature combined with some
atmospheric instability will help clear out the smoke more
efficiently over the coming afternoons.

Upper level troughing will also result lower daytime temperatures
for the interior. Temperatures will be below normals through the
extended forecast. The marine layer is deepening and extending
farther inland, and will be conducive to producing light drizzle
over the coming days especially for communities directly on the
coast.

The broad troughing and embedded shortwave disturbances will also
create low chances for rainshowers or perhaps thunderstorm
activity through the end of the week. A weak surge of monsoon
moisture associated with a shortwave disturbance may clip portions
of the southern zones Thursday, but even the most aggressive
models continue to keep the bulk of the moisture SE of Lake County
at this time. However, dry lightning potential exists through
Trinity County (5-10%), especially if the moisture flux ends up
more north than the high resolution models are suggesting.

A secondary wave will move NE over Northern California Friday into
Saturday morning. This disturbance will carry higher instability and
moisture (though still meager), giving a slightly higher chance for
some thunderstorm activity. This is mainly expected in western Siskiyou
County, but could impact portions of surrounding counties (5-10%
over Trinty County northward through far eastern Del Norte County,
and 10-15% over Siskiyou County and far northeast Del Norte).
There would be a potential for nocturnal activity late Friday as
well if storms occur at all. That said, this is still a very low
confidence forecast; however, it will still be watched very
closely due to historical poor model handling of the setup type
and the impact even a little lightning would have regarding fire
potential over the very dry vegetation. Smoke from the ongoing
MP18 fire near Hoopa will likely dampen instability (CAPE) over
the afternoon hours.


&&

.AVIATION...Stratus is particularly persistent today but alas
ceilings have lifted due to the passing, slow moving troughing
pattern. Intermittent periods of MVFR and IFR for KCEC will
continue as the unsettled pattern over the area fights between
stable air and weak instability. Flight categories at KACV will
not fair as well with extended periods of IFR and brief LIFR until
the evening hours when mostly LIFR prevail. Smoke plumes will
settle in overnight and get pushed eastward as the diurnal winds
pick up during the daytime. /EYS


&&

.MARINE...Strong northerlies continue in the outer waters but
will mostly ease tonight. Small craft advisories are out for all
area waters as the remnants of the passing Gale settles. The
northerlies will drop even more substantially Friday and
especially through the weekend as troughing continues to weaken
the pressure gradient. Seas will lower into and through the
weekend. Winds pick up again south of Cape Mendocino Saturday
morning with most of the northern waters void of strong winds.

&&

.FIRE WEATHER...A troughing pattern is taking effect over the
west coast, leading to good recoveries and also increases chances
for a deepened marine layer to infiltrate farther into the
interior. Increased mixing with local and general winds will
create continued afternoon gusts, especially for major valleys.

A weak surge of monsoon moisture associated with a shortwave
disturbance heading north up the  Valley has the potential to
interact the mountain creating localized afternoon storms.
However, even the most aggressive models keep the bulk of
moisture SE of Lake County at this time. That said it`s crucial to
pay attention for building clouds today as any storms could send
wind gusts channeling through terrain impacting ongoing fire
operations. This becomes especially if the moisture flux nudges
northwest beyond what the higher resolution models are suggesting.

A secondary shortwave will move NE over Northern California
Friday into Saturday morning. This disturbance will carry higher
instability and moisture (though still meager), leading to a
slightly higher chance for some thunderstorm activity (5-10% over
Trinty County northward through far eastern Del Norte County, and
15% over Siskiyou County and far northeast Del Norte). There would
be a potential for nocturnal activity late Friday as well if
storms occur at all. Storm movement Friday would be to the
north/northeast around 20 mph. Smoke from the ongoing MP18 fire
near Hoopa will likely dampen instability (CAPE) over the
afternoon hours, further lowering confidence on thunderstorm
coverage.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until midnight PDT tonight for PZZ450-
     455.

     Small Craft Advisory until noon PDT Friday for PZZ470.

     Small Craft Advisory until 6 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.

Visit us at https://www.weather.gov/eureka

Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka

For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png