139
FXUS66 KEKA 082107
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
207 PM PDT Sat Aug 8 2026

.KEY MESSAGES...
*Moderate to major heat risk continues through the weekend for
 much of the interior peaking today in most areas.

*Localized critical fire weather possible this weekend due to
 stronger afternoon valley winds and low relative humidity.

*Coastal stratus to continue for much of the North Coast today and
 tonight with continued chances for afternoon clearing.

*Temperatures diminish slightly next week, yet most inland areas
 remain in the upper 90s to around 100 through mid-week.

&&

.SYNOPSIS...Persistent high pressure aloft remains through the
weekend. Inland areas continue to see above normal temperatures
while the coast remains under marine stratus. Temperatures are
expected to gradually start cooling closer to normal next week.
An upper level trough off the coast may bring monsoon moisture and
the slight potential for thunderstorms late next week or next
weekend.


&&

.DISCUSSION...A steady ridge of high pressure remains entrenched
over the west coast leading to warm to VERY hot temperatures for
the inland areas. Most inland valleys can expect high temperatures
above triple digits today and close to, if not slightly above 100F
tomorrow. The coast continues to offer some relief from this
heat. Offshore stratus is blanketing much of the California coast,
yet satellite imagery shows mixing making its way from the OR
boarder southward. However, slightly above average SSTs and
offshore flow will contribute to limited development of prolonged
overcast conditions through the rest of the weekend.

Warming continues across the interior with moderate to localized
areas of major HeatRisk indicated. The heat is expected to peak
on today, particularly over Lake County, where conditions were on
the edge of warranting an excessive heat warning instead of only
an advisory. Regardless, this persistent heat will be dangerous
for anyone working outside and everyone in the interior portions
of all of Northern California should be drinking plenty of fluids
and taking breaks in the shade to avoid heat stroke or heat
exhaustion.

The aforementioned interior heating will tighten the surface
pressure gradient over NW CA forcing stronger onshore (NW) sea
breezes each afternoon and evening. With very dry conditions
across the interior this will result in increase fire weather
concerns. For more details, see the fire weather section below.

The upper level ridge that has settled over the area should
finally weaken and migrate eastward through early next week. A
secondary high pressure system is forecasted to set up over the
Pacific which will lead to weak troughing settling over the west
coast. This should allow temperatures to cool several degrees back
to around normal for this time of year and could lead to
increased likelihood of afternoon clearing of coastal stratus.
This may also start to bring the threat for inland thunderstorms
late next week or next weekend with there is enough moisture
associated with this evolving synoptic system.



&&

.AVIATION...18Z UPDATE...Coastal stratus remains across the
entire western seaboard today. Expect IFR/LIFR conditions for most
of the day along coastal terminals. Slight clearing is possible,
yet not expected from 19Z-00Z, better changes are for areas near
large river deltas compared to areas near steeper terrain. If it
does clear, overcast skies will return later this afternoon
between 02-04Z for most of the North Coast before developing to
fog late this evening. Winds will build to 10-15kts or so and will
be mostly northerly for most of the day along the coast. Wind
directions this will be dictated by coastal eddies forming and
migrating along the coastline.

Inland areas are expected to remain VFR with gusty afternoon
winds developing during the peak heating of the day. Upslope winds
will form through the morning and midday before NW winds dominate
the interior areas of NW CA. Anomalously hot temperatures for the
inland areas could lead to density altitude issues this afternoon
as well, be aware.


&&

.MARINE...Significant wave heights have been building through the
morning as northerly winds build steadily. Observations show gusts
up to 15-20kts which should increase through the afternoon,
especially further away from the coastline. Waves in the outer
waters are likely larger and steeper than the nearshore buoys are
recording due to the strongest winds expected downwind of Cape
Mendocino and Point St. George, where gale force gusts are likely
(>50% probability). These forecasted winds called for a Gale
Warning for the outer waters through the remainder of the
weekend, and likely longer into the middle of next week if long
range weather models hold fast. The inner waters are more likely
to see moderate to fresh breezes with steep waves due to
propagation from the fetch areas in the outer waters. The very
steep northerly waves have called for a small craft advisory for
the inner waters this weekend.

Plan your seafaring outings accordingly and always feel free to
reach out for any addition information regarding the marine
forecast for NW CA.


&&

.FIRE WEATHER...Stronger afternoon winds are expected to develop
for valleys this afternoon. Winds are already following the
channeled terrain and should increase with gusts up to 20 or even
25mph possible through the heat of the afternoon. These breezy
conditions are expected to expand to localized areas for several
hours this afternoon bringing critical fire weather Trinity,
northern and eastern Mendocino, and Lake Counties. While the
duration of the winds and low RH values are shorter than needed
for Red Flag status, it is important to remember that even a
single spark could start a wildfire in these conditions. Tonight,
higher elevations at or above 2,500ft can expect continued low RH
recoveries at or below 20% as a thermal belt develops at midslopes.
Sunday afternoon, breezy winds are expected again for several
hours, yet the RH is expected to be slightly higher than today.

Next week, temperatures are expected to slight cool as the upper
level ridge moves eastward. The new large scale weather set up
looks to have the potential for some dry thunderstorms next
Friday or Saturday. There is still a lot of uncertainty on this,
(moisture, lift, stability, etc.) but it definitely will need to
be watched and accounted for through the coming work week.


&&

.COASTAL FLOODING...Sea levels continue to run approximately 0.8
ft above the predicted tide level in Humboldt Bay. Tides will
become more amplified early next week following the normal lunar
cycle. The predicted tide at the North Spit is 7.95 ft MLLW at
10:21 pm on Monday the 10th and then 7.99 ft MLLW at 11:17 pm on
Tuesday the 11th. If the tide continues to run at around 0.8 ft
above predicted, this could result in minor coastal flooding
around Humboldt Bay with minor impacts in King Salmon and possibly
a few other locations around the bay.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory until 11 PM PDT this evening for CAZ105-106.

     Heat Advisory until 10 PM PDT Sunday for CAZ108-110>114-
     116>120.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 10 PM PDT Sunday for PZZ450-455.

     Small Craft Advisory until 3 PM PDT this afternoon for
     PZZ470-475.

     Gale Warning until 3 AM PDT Tuesday for PZZ470.

     Gale Warning until 10 AM PDT Monday 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