362
FXUS66 KEKA 122051
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
151 PM PDT Sun Oct 12 2025

.SYNOPSIS...A colder, wet storm system is forecast to arrive early
Monday, and will bring widespread rainfall, mountain snow above
4500-5000 feet, and the potential for thunderstorms. Light rain
showers will begin this evening, increasing in coverage and
intensity tonight through Monday. A drying and warming trend is
expected from mid week and into the weekend.


&&

.DISCUSSION....Latest satellite imagery depicts a shortwave
trough moving over the area this afternoon, bringing increasing
mid-to high-level clouds. Meanwhile, the next upper- level trough
drops southward toward the Cascades and Northern California from
western Canada. As of 12 PM, surface observations reported high
temperatures generally in the mid 50`s to mid 60`s. Chances of
precipitation gradually increase this evening and tonight. Pre-
frontal light showers or light isentropic upglide rainfall will
begin this evening.

Unsettled weather conditions are expected tonight through Tuesday.
The aforementioned upper level trough will evolve into a closed
low early Monday over western Oregon and southwest Washington, and
approaches the northern California with and associated surface
low. CAMs shows a line of organized convection activity along the
frontal system translating from northwest to southwest late
tonight through Monday morning, before shifting eastward late
Monday morning as the low moves over the area. Periods of moderate
to locally heavy rain rates is expected. Colder air aloft will
bring increasing instability on Monday, capable of producing brief
heavy downpours with thunderstorm potential over the coastal
waters and along the Mendocino coast. Progressive storm motions
will also preclude any major concerns for flash flooding or debris
flow. The rainfall total amounts has been updated per the Weather
Prediction Center (WPC), showing up to half of an inch less than
yesterday`s forecast across the interior due to the progressive
motion of this system. Rainfall total amounts are forecast to
range from 0.5 to 1.0 inches across much of the forecast area from
late tonight through late Tuesday, with the heaviest amounts up
to 1.5 inches over the west- southwest windward facing terrain.

Snow levels levels will start about 6000 feet tonight, before
lowering to around 4500-5000 feet Monday 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 from
5 to 11 inches of snow is expected for higher terrain in Trinity
and northeastern Mendocino counties. Snow levels are expected to
gradually rises to about 6000 feet Tuesday afternoon.

Monday night into Tuesday, showers will gradually be dwindling as
the the low moves south toward Central California. This is
expected to bring offshore flow across the interior, with an
uptick in showers across Trinity County Tuesday afternoon. Tuesday
night, areas of fog and patchy dense fog are expected to
developed into Wednesday along the shelter 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...VFR today will be replaced by lowering ceilings and reduced
visibility due to rain showers overnight as a cold front moves down
the coast. MVFR is likely at the coastal terminals with IFR possible
during the heaviest precipitation band as it sweeps through between
9Z and 13Z at CEC and ACV. Additional showers may persist behind the
heavier band of rainfall and the increased moisture could result in
lower ceilings into the morning hours. Rain will also spread inland
and south overnight into Monday morning bring low clouds to much of
the area and eventually to terminals in the far south, including
UKI, in the morning hours as the rain arrives. /RPA


&&

.MARINE...Northerlies have increased over the coastal waters with
small craft winds south of Cape Mendocino behind a departing
frontal system. Another system is approaching the area from the
north and this system will weaken the pressure gradient resulting
in lighter north winds tonight. 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 until 11 PM PDT this evening for
     PZZ455-475.

     Small Craft Advisory from 10 AM Monday to 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