485
FXUS66 KEKA 100742
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1242 AM PDT Mon Aug 10 2026

.KEY MESSAGES...

* Slightly cooler, but still hot, interior temperatures are
  forecast through Wednesday.

* Smokey conditions likely from the MP 18 Fire in the Trinity
  River Valley.

* Slight chance of interior thunderstorms late this week.


&&

.SYNOPSIS...High pressure starts to weaken this week, but slightly
above normal temperatures in the interior are expected through
Wednesday. Coastal areas continue to have near normal
temperatures with overnight stratus clearing in the afternoons
along with breezy northwest winds.


&&

.DISCUSSION...The seemingly immovable upper level ridge that has
dominated the weather for the past week or so has finally begun
to give way to more zonal flow aloft. This will begin the
"cooling" trend starting today, though interior temperatures will
still remain hot with the warmest valleys breaking 100. Still,
most areas will see highs a couple degrees cooler today. This
trend continues with interior valleys seeing highs in the high 90s
to just over 100 through Wednesday. Coastal areas remain in 60s
for much of the week with stratus forming each night and clearing,
at least partially, in the afternoons.

Daytime heating in the interior will continue to tighten the
surface pressure gradient each afternoon forcing stronger onshore
(NW) sea breezes. In NW-SE situated river valleys (Trinity River
Valley, Eel River Valley, areas near Clear Lake, etc.) these winds
will have a higher chance to mix down to the surface. These winds
along with hot and dry conditions will continue elevated fire
weather conditions this afternoon. For more details, see the fire
weather section below.

Despite the increased surface winds, the smokey conditions within
the Trinity River Valley will likely remain, depending on fire
containment, through midweek as the fire activity increases each
afternoon. The HRRR smoke model shows smoke moving along upvalley
flow before settling into valleys each night. This pattern is
expected to remain through Wednesday at the earliest.

Global ensemble models and 500mb clusters suggest that the midweek,
zonal flow aloft will likely evolve into weak to moderate troughing
by late week. The troughing will force a cooling trend with
inland temperatures struggling to break 90F by Friday. Troughing
could also create an environment capable of supporting afternoon
thunderstorms over the interior mountains. A lot of variability
remains regarding this weather threat, such as moisture available,
instability, or if there will be enough lift at the surface to
create updrafts. Stay aware of forecast changes as more details
become available through the week.


&&

.AVIATION...(06Z TAFs)...Coastal stratus has started to reform
around Humboldt Bay and IFR to MVFR conditions are likely around
ACV early this morning. Confidence is lower on stratus impacts at
CEC as northerly winds increase near Pt St George this morning.
This may be just far enough off shore and/or above the surface
inversion to prevent stratus from making it to the airport,
despite southerly surface winds being observed currently.
Regardless, IFR to MVFR stratus is likely to lift and scatter
shortly after sunrise. Interior areas outside the near-coastal
river valleys will remain VFR through the night. However, smoke
impacts in the Trinity River Valley may bring low visibilities
until winds pick up in the afternoon. VFR conditions (outside of
smoke) are likely by the afternoon with gusty northerly winds
likely at the coastal terminals.


&&

.MARINE...Gale force northerly winds remain persistent in the
outer waters and are likely to continue through Wednesday. Despite
lighter winds nearshore (peaking at 10 to 20 kts each afternoon),
steep seas of 7 to 9 ft are likely through Wednesday. High
pressure begins to weaken mid to late this week which will bring
relief to the strong northerlies. Steep seas will gradually ease
Thursday into Friday, which will give way for very mild
conditions across the waters Friday into the weekend.


&&

.FIRE WEATHER...A slight cooling trend is expected this week as
high pressure moves out of the area while weak troughing sets in.
Still, hot and dry conditions continue early this week. Afternoon
winds will not be as strong as this weekend`s but still is likely
to be locally elevated in channeled terrain. Gusts up to 20 to 25
mph are possible in the Trinity River Valley and around Clear
Lake this afternoon. Additionally, the higher elevations of Del
Norte will see gusty overnight east winds, which will lead to poor
to moderate overnight relative humidity recoveries. However,
relative humidity is expected to remain high enough outside the
highest ridges to avoid widespread critical conditions.

Troughing has the potential to funnel moisture into the area later
this week. The moisture, if it materializes over NW CA, could
result in some afternoon thunderstorms for Thursday, Friday, and
Saturday. Confidence remains low at this time and NBM
probabilities currently hover around 5 to 10% in Trinity and
Siskiyou Counties. This will be watched closely over the coming
days.


&&

.COASTAL FLOODING...Sea levels continue to run approximately
0.8 ft above the predicted tide level in Humboldt Bay. Tides will
become more amplified early this week following the lunar cycle.
The predicted tide at the North Spit is 7.95 ft MLLW at 10:21 pm
tonight and then 7.99 ft MLLW at 11:17 pm on Tuesday the 11th. If
the tide continues to run at around 0.8 ft above predicted, this
could result in minor coastal flooding around Humboldt Bay with
minor impacts in King Salmon and possibly a few other locations
around the bay.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     None.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 10 PM PDT Wednesday for PZZ450.

     Small Craft Advisory until 3 AM PDT Wednesday for PZZ455.

     Gale Warning until 10 PM PDT Wednesday for PZZ470-475.

&&

$$

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