623
FXUS66 KEKA 120747
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1247 AM PDT Sun Oct 12 2025

.SYNOPSIS...Areas of fog with some dense low visibility are
likely this morning along the sheltered valleys. Clear skies
overnight will promote strong radiational cooling. Cold air aloft
will promote near frost temperatures tonight. 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.


&&

.DISCUSSION...Areas of patchy dense fog are expected to developed
this morning along the shelter valleys with clear skies and
strong radiational cooling promoting the conditions. NBM has been
consistent with temperatures dropping to 32-36 F across the
coldest interior valleys in Trinity, northeastern Mendocino and
northern Lake counties. However, uncertainty persists regarding
frost conditions during the next few nights across the interior.
High dew point values in the mid 30`s to mid 40`s will preclude
frost conditions across the interior valleys in Trinity, interior
Mendocino and Lake counties.

A colder, wet system will drop south toward our area this
afternoon, and eventually move overhead Monday into Tuesday.
Generally light rain showers will begin to move over the area from
the north tonight into Monday ahead of the frontal system.
Operational deterministic models indicate the trough evolving into
a closed low over OR/WA early Monday. The potential for greater rain
rates increases early Monday into Monday afternoon as the cold
occluded front moves southward over the area. 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. Total rainfall
accumulation is forecast to range from 0.8 to 1.5 inches across
much of the forecast area later tonight through late Tuesday,
with the heaviest amounts up to 2.0 inches over the west-
southwest windward facing terrain. Lighter accumulation is
forecast for the Humboldt Coast and Del Norte Coast with total
rainfall from 0.5 to 0.8 inches.

Snow levels levels will start out around 5500-6000 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.

Ensemble model guidance is in good agreement with a high pressure
building over the area mid to late next week. This will promote
drier and warmer temperatures Thursday and into next weekend. /ZVS



&&

.AVIATION...(06z TAFs)...VFR to MVFR conditions are expected for
early Sunday morning for coastal terminals. Some interior valleys
could experience low clouds early Sunday; however, KUKI should
remain VFR through the TAF period. There is a strong signal of
clearing out to VFR Sunday morning before another round of rain
and low clouds approaches the area later in the day.


&&

.MARINE...Northerly winds are forecast to ramp up very early Sunday
and remain elevated into Sunday evening. At the moment, the sea
state is mostly controlled by a modest, mid period northwest swell
up to 7 feet. Northerly winds will begin to increase again early
Sunday morning, mostly for the southern waters where some near gale
force gusts are possible by early Sunday afternoon. Steep short
period seas will build over 6 feet in the southern waters through
Sunday night, but the northern waters will stay much more calm.
Winds will quickly calm again as showers move through early Monday
with the seas once again coming to be controlled by a moderate mid
period, northwest swell into mid next week. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 AM this morning to 11 PM PDT
     this evening for PZZ455.

     Small Craft Advisory until 11 PM PDT this evening 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