302
FXUS66 KEKA 092134
AFDEKA
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
234 PM PDT Wed Jul 9 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...The upper level low is moving out of the area and
high pressure is starting to build into the area. Temperatures are
generally similar to yesterday. Tonight offshore flow starts to
set up and this may help to limit the clouds along the coastal
areas. 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. Have issued a heat watch for the interior
portions of Humboldt and Del Norte counties with highs in some of
the valleys getting slightly warmer than 105. There is a lot of
uncertainty in these areas and how close this hot weather will
get to the coast. This may end up only being an advisory, but went
with a watch 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
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 and have not adjusted these yet. Sunday it
looks like there may start to be a southerly push of some marine
air so have ended the heat for advisory for portions of Mendocino
county on Saturday. Monday and Tuesday the hot weather is expected
continue, but may cool off by a few degrees. Again, the overnight
lows may be slightly too warm in some of the more protected
valleys.
&&
.AVIATION...Brief MVFR or VFR from prevailing IFR conditions is
expected this afternoon. Otherwise, expect IFR cigs to increase
again this evening and become widespread over the North Coast.
Conditions will worsen overnight 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 expected for the interior. Some low
level shallow turbulence will also be possible with stronger
northerlies flowing over the rugged and rough coastal terrain.
&&
.MARINE...Surface high pressure is forecast to re-build toward
the Northwest California coast today 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 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...Today is expected to be the be coolest and have the
highest RH for at least the next several days. High pressure is
building and offshore flow is expected with the warming and
drying. Tonight offshore flow is expected to set up in the near
coastal areas. This may not keep the stratus away, but it should
be more limited. Areas below the 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. This inversion 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 have lowered it by
blending with the FV3 model. This may not be low enough, but it
is a start. 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 from 8 PM this evening to 3 PM PDT
Thursday for PZZ455.
Gale Watch from Thursday afternoon through Thursday evening
for PZZ455.
Small Craft Advisory from 3 AM to noon PDT Thursday for
PZZ470.
Gale Warning from 1 PM Thursday to 11 PM PDT Friday for
PZZ470-475.
Small Craft Advisory until noon 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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