614
FXUS66 KEKA 052104
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
204 PM PDT Tue Aug 5 2025

.SYNOPSIS...Seasonable temperatures are forecast through Thursday.
Risk for heat-related illnesses will increase Friday through Sunday
with triple digit high temperatures expected in the interior.

&&

.DISCUSSION...

Dry upper trough will remain over the forecast area through much
of this week resulting in stable dry conditions and temperatures
near seasonal averages. A dry shortwave trough will progress
across the Pacific NW Wednesday through Thursday. This trough will
likely induce stronger onshore breezes across the interior valleys
and ridges, particularly in Lake, eastern Trinity and southern
Mendocino Counties. HREF and NBM 90th percentiles indicate peak
gusts from 25-35 mph.

A massive 500mb height anomaly will begin to build offshore and
toward the Pacific Northwest on Friday in the wake of this trough.
This warm dome of air coupled with dry offshore wind flow will
propel high temperatures 5-10F above seasonal averages on Friday.
The North Coast will probably warm into the lower to mid 70`s
on Saturday. It could warm to 70F or more on Friday too, but
onshore northerlies seem too strong and only McKinleyville and
Trinidad areas will have any chance to reach 70F.

The warm dome aloft will build over the area during the weekend
and interior temperatures will continue on an upward trend.
Widespread moderate HeatRisk is forecast Friday through Sunday,
primarily for the interior. NBM means and 50th percentiles are
around 102-107F for our typically valley hot spots. NBM 90th and
99th percentile max temps (108-115F degrees) for Trinity, NE
Humboldt and Del Norte over multiple days may yield much greater
HeatRisk than moderate. Potential exist for extreme heat over
multiple days. NBM probabilities for 108F or more are over 60%
along the Trinity and Klamath river valleys Sat and Sun. At the
moment it appears heat advisory will likely be necessary given the
areas of major HeatRisk. Stay tuned for updates. We will continue
to message the heat hazard on social media outlets and on our web
page via weather story.

Deep column of warm/dry air will likely keep temperatures in the
triple digits for mostly Trinity and NE Humboldt early next
week. Shallow marine air mass should gradually trickle into the
river valleys of Del Norte, western Humboldt and western
Mendocinco Counties early next week for some relief from the heat.
It will still be hot with highs over 80F in the coastal river
valleys all next week.

&&

.AVIATION...

(18Z TAFs)...VFR conditions are expected for the terminals of
Northwest California through very early Wednesday morning. This
afternoon, gusty northwesterly winds are anticipated for southern
interior Mendocino and Lake counties with gusts between 20 and 25
knots possible for this region. Very early Wednesday morning,
coastal stratus is expected to bring MVFR to potentially LIFR
ceilings. LIFR ceilings are expected at both KCEC and KACV a few
hours before sunrise. Low ceilings may lift into Wednesday
afternoon with some degree of high cloud-cover spreading over the
region with the passage of a dry front. /JLW

&&

.MARINE...

Gentle to fresh northerly winds will continue through Thursday
morning, with locally strong winds continuing downwind of Cape
Mendocino. A northwest swell is expected to build to around 5 to 6
feet at 10 to 11 seconds by Wednesday evening.

High pressure will begin to build into the region on Thursday,
tightening the pressure gradient Thursday evening and into Friday.
This will result in moderate to strong northerly winds, with the
strongest winds across the outer waters. Over the weekend, the
strongest northerlies are forecast to shift into the northern outer
waters.

&&

.FIRE WEATHER...

Where RH`s are less than 30%, wind gusts have been much less
compared to yesterday, generally 11-17 mph. Peak wind gusts
are more delayed compared to yesterday and winds should become
gusty around 20-25 mph late in the day in our typically drier
forecast zones; 264, 277 and 283. Overnight recoveries continue
to remain good, however higher elevations that extend into the
thermal belt may continue to have poor recoveries (<30%) and
gusty winds (>20 mph).

Another dry trough will track across the Pacific NW Wed through
Thu. Enhanced diurnal west to northwest breezes are expected once
again for our typically dry zones with RH`s from 20-30%  These
gusty winds coupled with low RH`s may yield elevated to locally
critical conditions again in the eastern Trinity, SE Mendocino
and Lake Counties for brief period.

Dry offshore flow (E-NE winds) and triple digit heat is forecast
Friday through Sunday in the interior. Magnitude and duration of the
heat and offshore flow remains uncertain. Current indications are
for the strongest offshore winds to occur over the mountains of
Del Norte County and windier ridges of Humboldt County.

Hot and dry weather will likely continue early to mid next week.
Coastal areas should moderate with return of a shallow marine
layer and coastal low clouds and fog.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 11 AM to 11 PM PDT Thursday for
     PZZ470-475.

&&

$$

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