Yorkville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

226
FXUS66 KEKA 060703
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1203 AM PDT Sat Sep 6 2025

.SYNOPSIS...There is a slight chance of thunderstorms in Trinity
County this afternoon. A cooling trend continues in the interior
through the weekend and early next week. Wet weather and below
normal temperatures are expected Monday and Tuesday with a gradual
warming and drying trend possible later in the week.


&&

.DISCUSSION...The main upper level low that is impacting the area
continues to spin well off the Washington and British Columbia
coast. Another shortwave is moving onshore early this morning and
this is expected to bring more fog and drizzle and keep the deeper
marine layer. Some clearing along the coast is possible in the
afternoon as the marine inversion wakens. The shortwave does
introduce some upper-level moisture and instability to the area. A
few showers and isolated thunderstorms in the interior are possible
this afternoon and evening. Several CAMs are showing a few cells of
modeled reflectivity in northern Trinity County. PWATs of 0.8-1 inch
will likely support some precipitation, but fast storm motions could
support a few dry lightning strikes. Some model soundings do show a
mid-level capping inversion, which does lower confidence in
thunderstorms.

Tonight into Sunday morning, the marine layer is expected to remain
deep and there will likely be widespread clouds along the coast and
into the river valleys. Coastal drizzle is expected again. Sunday
afternoon there is expected to be some light southerly winds, and,
along the with the weak inversion, there could be some additional
afternoon clearing at the coast.

Sunday night into the Monday, the main upper level trough and an
associated front moves onshore, bringing rain to parts of the area.
High resolution models are starting to resolve the system, and it
looks showery which brings the potential for heavy rain and perhaps
thunderstorms. Confidence is low on thunderstorms and NBM thunder
probabilities have been trending downward over the last couple days.
Still, temperatures aloft will cool, steepening lapse rates and
providing some instability. There is a nonzero, but low, threat for
flash flooding over the burn scars of Del Norte and Humboldt if
heavy rain does occur. This will need to be watched.

Rain amounts in Humboldt, Del Norte, and Trinity Counties range from
around half an inch to slightly over an inch in the higher terrain.
The NBM probabilities for over an inch in 24 hours is around 30-40%
for areas of Del Norte, northern Humboldt, and the higher terrain of
northern Trinity County. Probabilities for at least a tenth of an
inch are above 70% in Del Norte, Humboldt, and Trinity counties,
Chances drop to around 50-70% into Mendocino County, and 40-50% in
Lake County. Much cooler temperatures are forecast for the interior,
with highs largely in the 70`s for most of the valleys.

Tuesday and Tuesday night the potential for heavier rain starts to
diminish fairly quickly. The probability of over a half inch in 24
hours drops below 50 percent on Tuesday and Tuesday night. Only the
higher mountains of Del Norte, Humboldt, and Trinity counties have
over a 30 percent chance of receiving a half inch. Some of the
deterministic runs are even showing this period as mainly dry now.
Moisture and heating could support showers or thunderstorms in
northern Trinity county, which could bring more rain, but confidence
is lower on this.

Wednesday and Thursday the ensemble model clusters start to diverge
on how quickly the ridge builds into the area. Some of the models
show drying as early as Wednesday while others keep rain into
Thursday. This will also have a big impact on how quickly temperatures
warm back up and things dry out in areas that got rain. JB/MKK


&&

.AVIATION...(06Z TAFs)... General onshore flow will continue to push
stratus inland into Saturday morning. A deep marine layer with a
depth to around 3500 feet along the North Coast continues into
Saturday. Patchy drizzle is expected to occur along the coast with
this saturated layer. Expect mainly MVFR ceilings through Saturday
monring. Light variable winds are expected along the coast into
Saturday.

For inland areas: Another period of MVFR ceilings are expected once
again at UKI early Saturday morning with a slightly deeper marine
layer. Any low clouds are expected to clear out at UKI with the
diurnal heating Saturday morning around mid morning. /ZVS


&&

.MARINE...Generally light to gentle northerly breezes will prevail
into mid morning. Winds will gradually shift to southerlies and
slightly increase ahead of a frontal system this Saturday and into
Sunday. Small, mid- period NW and SW swells will persist through the
weekend. Otherwise, relatively calm conditions with light winds and
seas below 5 feet are expected across the coastal waters this
weekend and early next week as an area of low pressure approaches
from the west.

Monday, there is a chance (15-25%) of thunderstorms in the wake of
the front on Monday, especially north of Cape Mendocino. Lightning
strikes and erratic gusty winds are possible with the strongest
storms. /ZVS


&&

.FIRE WEATHER...An approaching shortwave is bringing a deeper marine
layer to the area and increased relative humidities. Cooler air and
increased moisture aloft along with warm afternoon temperatures
increases instability. A few showers and thunderstorms are possible
in the afternoon and evening hours, with the greatest chances in
Trinity County. These storms look fast moving, so dry lightning is a
threat, but uncertainty is high. Cooler temperatures, higher RH,
and rain is likely Monday. Thunderstorms are possible again Monday
across the area, but these will be accompanied by rain. Some areas
of heavy rain are possible. Warmer and drier weather is possible
later next week. JB


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&

$$

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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