Humboldt Hill, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

183
FXUS66 KEKA 100721
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1221 AM PDT Thu Jul 10 2025

.SYNOPSIS...High pressure is building and generally hot and dry
weather is expected for the next week or so. The hottest
temperatures will start in the south on Friday and work their way
north on Saturday and Sunday. Northeast winds overnight on
Thursday and Friday will help to limit the stratus and potentially
bring warmer temperatures to the coast.


&&

.DISCUSSION...Offshore flow starts to set up and this may help to
limit the clouds along the coastal areas this morning. Thursday more
warming is expected as high pressure starts to build into the area.
Thursday night offshore flow is expected again and this may help
keep stratus away from the coast once again. Highs at the coast may
be in the middle to upper 60s on Friday. Inland areas are expected
to see highs slightly over 100 in many of the valley locations.
There is quite a bit of uncertainty on how close this will get to
the coast. So for now just have a heat advisory for interior
Mendocino, Trinity and Lake counties. This may need to be expanded
to portions of interior Humboldt county if these areas heat up
faster than expected.

The heat continues to build on Saturday and expands north and
towards the coast. A heat watch for the interior portions of
Humboldt and Del Norte counties has been issued due to highs in some
of the valleys possibly being hotter than 105. There is a lot of
uncertainty in these areas in regards to how close this hot weather
will get to the coast. This event may end up only being an advisory,
but a watch was issued due to the uncertainty. The heat advisory for
Trinity, Mendocino and Lake counties continues into the weekend as
well. Another source of uncertainty is the low temperatures. NBM
looks like it is running too warm for the lows in the valleys, so we
manually lowered these in some valleys on Friday and Saturday.

Sunday the heat risk is showing that the advisory may need to be
upgraded to warning in Trinity county, but it looks like this is
based on overnight temperatures that have not adjusted these yet due
to model data not going out that far yet. Sunday may be the start to
be a southerly push of marine air. This was the reasoning for the
end of the heat for advisory for portions of Mendocino county on
Saturday. Monday and Tuesday the hot weather is expected continue,
but the high temps may cool off by a few degrees.

&&

.AVIATION...IFR cigs are increasing and becoming more widespread
over the North Coast. Conditions will continue to deteriorate to
LIFR with possible 1SM or less in fog at coastal aerodromes (KACV
and KCEC) as winds become calm or light and a lower more stout
inversion develops. Other than smoke and haze obscuration reducing
slant-wise visual ranges and some coastal low clouds along the
Mendocino coast/Eel river valley, VFR and clear skies are expected
for the interior. Some low level shallow turbulence will also be
possible with stronger northerlies flowing over the rugged and rough
coastal terrain. Clearing is expected along the coast for a brief
time Thursday afternoon, before marine stratus redevelops into the
evening.


&&

.MARINE...Surface high pressure is forecast to re-build toward
the Northwest California coast through Thursday. This will enhance
the pressure gradient and once again strengthen the northerlies.
Gale force winds and large steep waves are probable (>80% chance)
over the outer waters Thursday afternoon through Friday night. Gale
force winds and/or very large steep waves will likely persist into
at least Sat for the northern outer waters (PZZ470). Closer to shore
and across the inner waters, gale force gusts are probable around
and downwind of Cape Mendocino and Pt St George. The coverage of
gale conditions appears insufficient to warrant a gale warning.
There still may be impacts for mariners traversing these strong wind
corridors, so we will message this in a probabilistic graphic
utilizing HREF wind gusts which is not calibrated or bias corrected
and most likely overdone.


&&

.FIRE WEATHER...High pressure is building and offshore flow is
expected with the warming and drying inland and near coastal
areas. This may not keep the stratus away, but it should be more
limited. Areas below the marine layer inversion, which is
expected to be around 3000 feet, are expected to see good RH
recoveries while areas above it will be much drier and see breezy
northeast to east winds. There is still quite a bit of uncertainty
on how deep this inversion will be, yet it is expected to be
shallower on Friday as the high pressure squashes it down. There
is a lot of uncertainty on how low the afternoon RH will get in
Humboldt and Del Norte counties. The NBM is likely too high due to
the pattern shift from a deep marine layer. So it has been
lowered it by blending it with the FV3 model. This may not be low
enough, but it is a nudge towards higher accuracy. 850 and 925 mb
winds are around 10 to 20 mph overnight. Warmer dry conditions
are generally expected on Saturday, although portions of Mendocino
county closer to the coast may start to see more marine influence
as the flow aloft weakens.

Smoke across the area will mainly be pushed south from the Butler
Fire. This will trend more towards the west overnight and back to
the east in the afternoon when the winds become more northwesterly.
The eastern portions of the area may also see some smoke from the
Green Fire north of Redding in the afternoons starting on Thursday.
MKK


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Extreme Heat Watch from Saturday morning through Sunday
     evening for CAZ102-105-106.

     Heat Advisory from 11 AM Friday to 11 PM PDT Sunday for
     CAZ107-108-111-114-115.

     Heat Advisory from 11 AM Friday to 11 PM PDT Saturday for
     CAZ110-113.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 5 PM Thursday to 3 AM PDT
     Saturday for PZZ450.

     Small Craft Advisory until 3 PM PDT Thursday for PZZ455.

     Gale Watch from Thursday afternoon through Thursday evening
     for PZZ455.

     Small Craft Advisory from 3 AM to 1 PM PDT Thursday for
     PZZ470.

     Gale Warning from 1 PM Thursday to 11 PM PDT Friday for
     PZZ470-475.

     Small Craft Advisory until 1 PM 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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