804
FXUS66 KEKA 130750
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1250 AM PDT Mon Oct 13 2025

.SYNOPSIS...A colder, wet storm system is forecast to arrive today,
and will bring widespread rainfall, mountain snow above 4500-5000
feet, and the slight potential for thunderstorms over the coastal
waters. Light rain showers will be increasing in coverage and
intensity through the day. A drying and warming trend is expected
to take effect mid week into the weekend.

&&

.DISCUSSION...Satellite imagery depicts the upper level trough
moving towards NorCal, bringing increased mid-to high-level clouds
with radar showing spotty rainshowers. Chances of precipitation
gradually increase through tonight as pre-frontal light showers or
light isentropic upglide rainfall will continue to fall through the
evening

Unsettled weather conditions are expected through Tuesday. The
aforementioned upper level trough will evolve into a closed low
early this morning over western Oregon and southwest Washington
before approaching Northern California with an associated surface
low. CAMs shows a line of organized convection activity along the
frontal system translating from northwest to southwest through the
morning, before shifting eastward later this morning as the center
of the low moves over the area. Periods of moderate to locally heavy
rain rates are expected. Colder air aloft will bring increasing
instability, capable of producing brief heavy downpours with
thunderstorm potential over the coastal waters, especially for the
Mendocino coast. Quick storm motions will preclude any major
concerns for flash floods and/or debris flows. The rainfall total
amounts are forecast to range from 0.5 to 1.0 inches across much of
the forecast area from now through late Tuesday, with the heaviest
amounts up to 1.5 inches over the west- southwest windward facing
terrain.

Snow levels are currently sitting at about 6000 feet, before
lowering to around 4500-5000 feet late this morning. Some light
mountain snow is expected on Scott Mountain Pass. Total accumulation
over Scott Mtn pass is expected to be between 2-4" from Monday
morning through Monday night. Higher snow amounts range from 5 to 11
expected for higher terrain in Trinity and northeastern Mendocino
counties. Snow levels are expected to gradually rises to about 6000
feet Tuesday afternoon.

Tonight into Tuesday, showers will gradually be dwindling as the the
low moves southward toward central California. This is expected to
bring offshore flow across the interior and an uptick in showers
across Trinity County for Tuesday afternoon. Tuesday night, areas of
fog and patchy dense fog are expected to developed into Wednesday
along the sheltered valleys with clear skies and strong radiational
cooling.

Pattern change on Wednesday as the low shift eastward and high
pressure begins to builds in toward the region. This will bring a
drying and warming trend from mid week into the weekend, with
seasonal average high temperatures back on Friday. /ZVS

&&

.AVIATION...(06z TAFs)...Isolated to scattered showers have already
begun along the Del Norte and Humboldt coasts. Showers will continue
into the region early Monday morning with VFR to MVFR conditions.
The more consistent rain will begin around Del Norte and Humboldt
counties around 12Z and continue southeast reaching Mendocino and
Lake counties between 15z and 18z. There could be periods of
moderate to heavy rainfall during those times, resulting in
periods of IFR/LIFR conditions. Rain will continue out of the area
Monday afternoon through Monday evening.

&&

.MARINE...Another system is approaching the area from the north.
This system will weaken the pressure gradient resulting in lighter
north winds early Monday morning. However, this next system will
bring a mid-period fresh swell to the waters, building to between 9
and 12 feet in the outer waters zones on Monday into Tuesday. The
coastal buoys off of Oregon are indicating the swell is larger than
the model guidance by a foot or two near the coast. Thus, the
forecast wave heights have been increased above guidance and solidly
into small craft levels over 10 feet. Thus, a new small craft
advisory has been lifted for the northern outer waters zone and an
additional small craft will be needed south of Cape Mendocino once
the current small craft expires.

Northerly winds will not be as strong with this passing front, but a
few gusts to near 30 kt will be possible on the far northwestern
portion of the northern outer waters zone off of Point St. George
Monday night before winds subside. Winds near the immediate coast
may become southerly Tuesday into Wednesday as an upper low spins
south of the area. A return to strong northerlies is anticipated
late in the week as high pressure builds back over the eastern
Pacific. /RPA

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 3 PM this afternoon to 3 PM PDT
     Tuesday for PZZ455-475.

     Small Craft Advisory until 3 PM PDT Tuesday for PZZ470.

&&

$$

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