214
FXUS66 KEKA 200700
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
1200 AM PDT Wed Aug 20 2025

.SYNOPSIS...Hot and very dry weather will build in through the week
with a shallower and stronger marine layer along the coast. There is
very slight potential for thunderstorms over the interior this
weekend into early next week.


&&

.DISCUSSION...Over the past few days a shortwave trough
lingering along the Pacific Northwest coast has allowed for cooler
than normal temperatures across the interior and for a weak, easy to
clear marine layer along the coast.

Conditions will gradually but starkly change through the week as
strong high pressure begins to stretch across from the 4 corners
region. Interior highs will most likely return to near 100 by
Thursday and peak between 105 and 110 by either Friday or Saturday.
Though not quite record breaking, it`s getting late in the season
for such hot temperatures. Daytime heat, combined with enhanced
overnight lows in the mid 60s will combine to generate generally
moderate to localized major (in the Trinity River Valley and Russian
River Valley mostly) HeatRisk.

High pressure will generally promote a shallow but more resilient
marine layer along the coast, likely encouraging a stronger deck of
marine stratus late in the week, especially with more persistent
onshore flow. That said, a weakening in the wind may allow for some
hotter air to creep closer to the coast this weekend with slight
potential (25% chance) for coastal highs near 70 on Saturday. Most
model ensembles show high pressure slowly weakening early next week.
/JHW


&&

.AVIATION...Stratus remains along the coast north of Cape Mendocino
this morning. This is expected generally remain in or very near KCEC
and KACV. It appears to be expanding, but there is some offshore
flow developing which could push it offshore again this morning.
Confidence is very low on this so have left them LIFR overnight.
later this morning the inversion is still fairly weak and should
allow for some decent clearing this afternoon. There is also
expected to be some gusty winds of 10 to 20 along the coast and that
may help clear skies out as well. Tonight stratus is more uncertain
on it`s return and how quickly this will occur. The HREF shows KCEC
remain clearing overnight, but low clouds returning quickly at KACV.
MKK


&&

.MARINE...High pressure is building into the area this morning.
Northerly winds are expected to continue to strengthen over the next
several days. One of the lower confidence parts of the forecast is
how close these stronger winds will get to shore. For now the hires
models are showing them mainly beyond 5 NM from much of the area
north of Cape Mendocino. So have not added a small craft advisory
to the northern inner waters, but as it gets closer this could be
needed. South of Cape Mendocino it looks like they may move in
closer to the coast by Wednesday afternoon and linger overnight. So
have added a small craft advisory for the southern inner waters.

The winds are expected to continue to increase and likely peak on
Thursday around 20 to 25 kt. There will be some gusts to 35 kt, but
at this point it doesn`t seem like a gale warning will be needed.
This could change as we get more into the range of HIRES models.

Waves are currently dominated by a 3 to 4 foot wave at 10 seconds.
This is expected to diminish and get absorbed into the other wave by
Wednesday night. This afternoon a small southwest wave around 15
seconds is expected to move into the waters, but is expected to peak
around 2 feet and linger through the weekend. MKK


&&

.FIRE WEATHER...Building hot and very dry weather over the next
several days will generally increase fire danger and dry fuels back
out after several days of relief. Though light rain last weekend was
enough to moisten fine fuels, live and larger fuels continue to be
near peak dryness for all interior areas. RH late this week will
drop to some of the lowest of the season so far with some single
digit minimum RH possible in the feat eastern interior.

Beyond hot and dry weather, the main concerns will be for potential
thunderstorms late in the week and this weekend. Heat will greatly
increase surface instability, but moisture will generally be lacking
to generate thunderstorms. By around Sunday, there is some
indication of monsoon moisture wrapping around and up into the
Central Valley, but the general pattern will be much more conducive
to storms over the central Sierras (20% chance there) rather than NW
California (only 5% thunder chance here). There is some potential
for a more concerning pattern around next Monday with moisture
possibly wrapping back out to the coast. This potential will have to
be watched closely. /JHW


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     Heat Advisory from 11 AM Friday to 11 PM PDT Saturday for
     CAZ105-106-110-113.

     Heat Advisory from 11 AM Thursday to 11 PM PDT Saturday for
     CAZ107-108-111-114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 4 PM Wednesday to 2 AM PDT Friday
     for PZZ455.

     Small Craft Advisory from 11 PM Wednesday to 10 PM PDT
     Friday for PZZ470.

     Small Craft Advisory until 4 AM PDT Saturday 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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