818
FXUS66 KEKA 030720
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1220 AM PDT Wed Sep 3 2025

.SYNOPSIS...Isolated dry thunderstorms inland remain possible through
early tomorrow morning. One last day of hot temperatures likely
for the interior. Stratus likely for the coastal areas with
marginal short-lived clearing. Another upper level low/trough
will bring a slight chance of showers, perhaps some thunderstorms,
across the northern portions of the area Thursday and Friday.

&&

.DISCUSSION...Tonight, lingering chances (15%) of showers and
thunderstorms are expected over the northeastern portion of Trinity
County with showers as the trough continue to move northward. CAMs
show weak returns over the Trinity Horn while moderate to strong
returns farther east and north of the area through the early
hours of the morning today. Dry low levels and DCAPE over 1000
J/kg support gusty outflow winds of up to 40-60 mph for any storms
that do form.

Through today, the shortwave disturbance begins to move northward
and the weather quiets down. A larger upper level trough is expected
to gradually approach the area from the west pushing the warmer air
ridging off to the east. This may help to weaken the low level
inversion, allowing a period of clearing skies long the coastal
areas in the midday to the afternoon.

Thursday and Friday, an upper level low/trough will approaches the
area. The winds aloft shift to the southwest. This will bring a
slight chances (10-20%) of showers across the northern portion of
the forecast area, especially for Del Norte County. GFS and NAM
suggest an increasing instability over interior Del Norte and
northern Trinity counties on Thursday and Friday. Sounding models
show elevated instability with an inverted V over Trinity County on
Thursday. Temperatures are expected to steadily decrease diminish
by a degree or two in most areas today and Thursday.

On Friday and Saturday, more significant cooling is expected with
interior highs in the high 80`s to low 90`s Friday and the 80s
mainly on Saturday. The coastal inversion will be fairly weak by
this point and it may allow the coast to clear out allowing weekend
temperatures in the mid 60s. /ZVS

&&

.AVIATION...Coastal clouds have settled into a thick fog in the
Humboldt Bay area tonight with visibilities less than a quarter mile
at times. Farther north some light offshore flow has allowed
ceilings to remain a little higher with LIFR to IFR. Elsewhere fog
has expanded to the entire Mendocino coast and has expanded into
some of the near-coastal valleys. VFR is prevailing elsewhere though
high clouds have streamed over the area from thunderstorms to the
west. Coastal cloudiness may be quite persistent on Wednesday with
lighter near-coast winds and a strong inversion. /RPA

&&

.MARINE...Though northerly winds are not particularly strong, an
extended fetch into the Oregon coastal waters is allowing for steep
short period seas to develop across the outer waters zones. Thus,
small craft advisories are in effect through Wednesday night. Winds
and seas will decrease on Thursday into Friday as an upper trough
moves overhead weakening the surface pressure gradient. /RPA

&&

.FIRE WEATHER...There remains a slight chance (~10%) of isolated dry
thunderstorms in the interior through this evening with increasing
instability this evening and overnight, primarily for Trinity
County. CAMs show the potential for nighttime convection as winds
aloft shift offshore late tonight. IF storms form, hazardous gusty
and erratic outflow winds of 40 to 60 mph are possible. Even if no
storms form, fire danger is expected to be of concern. The overall
atmospheric instability will increase ventilation/mixing allowing
for more fire growth and the potential for plume dominated
potential. The high afternoon mixing heights could also mix down
wind gusts of 25 to 30 mph in the higher terrain and exposed areas.
A Red Flag Warning remain in effect until 5AM PDT this evening for
Fire Weather Zones 204 and 283 due to the overnight convection
threat.

Wind threat is decreased today to usual diurnal flow with afternoon
gusts, but warm temperatures and very low afternoon RH with poor
overnight recoveries in the high elevations are forecast to continue
through Thursday. An approaching upper level low/trough will bring a
slight chances (10-20%) of precipitation across the northern portion
of the area Thursday and Friday. With this passage nighttime
recoveries could be close to 100% creating valley fog. The low
pressure passage will also decrease atmospheric stability, with the
potential of isolated thunderstorms across interior Del Norte and
northern Trinity counties. Cooler weather with below normal
temperatures and generally higher relative humidity for this
weekend.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Red Flag Warning until 5 AM PDT early this morning for
     CAZ204-283.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 PM PDT Thursday for PZZ470.

     Small Craft Advisory until 3 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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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png