230
FXUS66 KEKA 181822
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1122 AM PDT Fri Jul 18 2025

.SYNOPSIS...Conditions will remain hot and dry inland, while a
deepened and a relatively persistent marine layer keeps temperatures
cooler along some portions of the immediate coast. Cool down
expected early next week.


&&

.DISCUSSION...Strong ridging will build into the region following a
weak upper trough. Already warm temperatures will continue to
increase into the mid-90`s across interior valleys for Saturday and
Sunday. NBM probabilities for highs >90 degrees are >80% as far as
Redway and Laytonville as warm temperatures chip away at the marine
layer. Areas of Moderate HeatRisk in interior Trinity, Humboldt and
Mendocino will be a concern for sensitive individuals. Breezy
terrain driven winds expected across the interior each afternoon.
Otherwise, daytime highs will be significantly dampened along the
coast with a persistent marine layer. Areas of coastal drizzle are
possible on Saturday morning, after which the marine inversion will
begin to compress and remain slightly closer to the coast, likely no
longer reaching Ukiah by Sunday. An approaching upper trough will
help to tighten the coastal pressure gradient Sunday into Monday -
gusty northerlies south of Cape Mendocino expected, including Lake
County (SW flow in higher elevations of eastern Lake County). This
will pose a slight fire weather concern as daytime RH`s are still
25 to 30%.

High pressure will begin to break down beginning early next week as
a positively tilted upper trough over WA/OR begins to extend into
NorCal. Temperatures are expected to cool off significantly with
highs in the upper 70`s to mid 80`s (with isolated valleys
potentially reaching 90) through midweek. Long range models show
anomalously low heights sitting over the eastern Pacific/PNW through
at least Wednesday with generally northerly flow and terrain
driven afternoon winds expected. NBM beginning to hint at a chance
for thunder Tuesday and Wednesday afternoon with cool upper
temperatures and mid level moisture availability, but there is
still high uncertainty.


&&

.AVIATION...(18Z TAFs) Another day of Stratus along the coast today.
LIFR/IFR conditions are present at terminal sites with minimal
clearing expected. brief periods of VFR are possible as mixing at
the surface clears out the clouds, yet stratus and fog is expected
to return again this evening leading to LIFR conditions once again.
Dense fog with a 30% probability of degraded visibilities under 1SM
at KACV and KCEC and cloud ceilings <500ft are likely with 50-60%
probability of reforming again overnight.

Inland terminals can expect VFR conditions, light elevated winds, and
even potential smokey skies today. Fog returning to river valleys is
expected again tonight. KUKI shows about a 20-30% probability of fog
returning its way up the Russian river valley, however low RH model
outputs and minimal southerly wind keeping it unlikely.


&&

.MARINE...High pressure is beginning to build back toward the coast
over the eastern Pacific Ocean forcing a return of the northerly
winds. The pressure gradient will continue to tighten into the
weekend with moderate to strong northerly breezes Saturday and
Sunday, with the strongest winds over the outer waters zones and
downwind of Cape Mendocino. Seas will build in size as short period,
steep wind waves form due to the persistent winds. Small craft
advisories have been hoisted from Saturday to Sunday over the outer
waters due to these steep seas and breezy winds. Winds and seas will
subside early next week due to another upper level trough diving
south over the coastal waters, weakening the surface high pressure
gradient that causes our strong northerly winds. Light winds and low
seas are anticipated for much of the coming work week.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 PM Saturday to 5 PM PDT Sunday
     for PZZ470.

     Small Craft Advisory from 3 PM Saturday to 11 PM PDT Sunday
     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