384
FXUS66 KEKA 280726
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1226 AM PDT Mon Sep 28 2026

.KEY MESSAGES...

* Localized frost across wind-sheltered interior valleys early
  this morning.

* High pressure builds mid-to-late week, bringing an extended dry
  period with interior valley high temperatures warming into the 80s
  and 90s.

* An arriving long-period west-northwest swell brings an elevated
  risk for sneaker waves along ocean beaches today.

* Fresh northerly winds continue south of Cape Mendocino, where a
  Gale Warning remains in effect for the southern outer waters.


&&

.SYNOPSIS...An exiting upper trough will allow strong overnight
radiational cooling to trigger localized frost across sheltered
interior valleys early today. Upper-level ridging builds over the
West Coast mid-to-late week, supporting a progressive inland
warming trend and dry conditions through next weekend.


&&

.DISCUSSION...Water vapor satellite loops show the primary 500 mb
shortwave trough axis advancing east toward the Great Basin. Light
boundary layer winds and post-frontal dry air will maximize
radiational cooling through daybreak, keeping localized frost
risks focused within sheltered interior valleys. Broad mid-level
ridging over the eastern Pacific will expand inland Tuesday
through Friday, establishing high confidence in dry conditions
across the region.

At the surface, the onshore pressure gradient between the offshore
eastern Pacific high and the interior thermal low will drive fresh
northerly winds, strongest south of Cape Mendocino. Strong
atmospheric sinking beneath the upper ridge will steadily warm the
air mass aloft. Thermal profiles across interior valleys will
support afternoon maximum temperatures climbing into the 80s and 90s
mid-week. Ensemble guidance highlights an 80% probability of
interior valley highs exceeding 90F Wednesday and Thursday.


&&

.AVIATION...A shallow marine layer will bring intermittent MVFR to
IFR ceilings to coastal terminals (KACV and KCEC) overnight, with a
2030% chance of brief LIFR visibilities in patchy fog around dawn.
Ceilings will clear to VFR by late Monday morning as northerly
boundary layer flow increases mixing. Inland areas, including
regional terminal KUKI, will maintain prevailing VFR conditions
under clear skies. Due to an ongoing ASOS comms outage at KUKI,
automated observations are unavailable and amendments are not
scheduled.


&&

.MARINE...Fresh northerlies continue due to the pressure gradient
between offshore high pressure and the interior thermal trough.

* Northern Inner Waters: Northerlies of 10 to 20 kt will generate
  steep short-period seas. A west-northwest swell at 15 to 17
  seconds arrives today. A Small Craft Advisory remains in effect
  through late tonight.

* Northern Outer Waters: Northerlies of 20 to 25 kt with gusts to
  35 kt will build combined seas to 1112 ft. A Small Craft
  Advisory remains active through late tonight.

* Southern Inner Waters: Fresh to strong northwest winds of 20 to 25
  kt with gusts to 35 kt will maintain steep seas. A Small Craft
  Advisory remains in effect through Tuesday morning.

* Southern Outer Waters: Gale force conditions develop in the lee
  of Cape Mendocino, where northerly winds of 25 to 30 kt with
  gusts up to 40 kt will yield steep, hazardous combined seas of
  13 to 15 ft. A Gale Warning remains in effect this afternoon
  through Tuesday afternoon.


&&

.BEACH HAZARDS...A long period west northwest swell at 3 to 6 ft with
a period up to 17 seconds will build in today. This swell will
bring a moderate risk for sneaker waves. A smaller 3 ft long
period south swell will also bring some risk for sneaker waves for
south facing beaches. High astronomical tides will increase the
danger, especially over rocks and jetties.

Sneaker waves are a unique hazard, with up to 30 minutes between
waves. Large, unexpected waves can sweep across the beach without
warning, sweeping people into the sea from rocks, jetties, and
beaches. These sneaker waves can also move large objects such as
logs, crushing anyone caught underneath. Even ankle to knee deep
water can knock you down and drag you out when a sneaker wave hits.
Pay attention and stay above the high water line and any wet sand to
stay safe. If the ground is wet, waves have surged.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Tuesday for PZZ450-470.

     Small Craft Advisory until 9 AM PDT Tuesday for PZZ455.

     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ475.

     Gale Warning from 3 PM this afternoon to 3 PM PDT Tuesday
     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