Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 161117

National Weather Service Eureka CA
417 AM PDT Mon May 16 2022

.SYNOPSIS...Deep marine layer clouds and drizzle toward the coast
will give way to some sun this afternoon, accompanied by a cooler
onshore breeze. Pacific high pressure remains in control Tuesday
with plentiful sunshine, brisk onshore breezes and warm afternoon
temperatures inland. A passing front on Wednesday may bring a
little light rain near the Oregon border. Cooler air will follow
on Thursday, with brisk northerly winds and sunshine to end the


.DISCUSSION...An upper-level trough is swinging toward the Pacific
Northwest this morning, with surface low pressure pushing onshore
in British Columbia, while a trailing cold front extends all the
way southward to near the California/Oregon border. This front
will make little headway into our region though, and is only
acting to deepen existing marine layer moisture and cloudiness.
That marine layer extends all the way above 4000 feet according to
the ACV profiler, with the GOES-17 Night Fog product showing
stratus spilling all the way up to Willow Creek, and even up the
Mad River Valley to Ruth. The marine layer is not as deep in
Mendocino County due to the ridge to our south, but still is
pushing 3000 feet as stratus reaches Willits and even Ukiah for
awhile this morning. A trailing shortwave trough is triggering
some high cloudiness offshore, which will push across our region
today. However, it looks relatively thin on satellite compared to
what the NBM and HREF are suggesting, so expect a fair amount of
filtered sunshine across the interior today, with high
temperatures perhaps only a few degrees cooler than Sunday.

In the wake of that trough, stronger Pacific surface high
pressure will be building in toward the coast today, bringing much
stronger onshore breezes than we have seen for quite some time.
That will help mix the marine layer and allow for some partial
clearing later today toward the coast, but clouds may hang tough
over portions of inland Humboldt County through the afternoon. As
northwest to west winds calm down tonight, lingering low-level
moisture will pack into the Eel River valley with clouds filling
back in across much of western Humboldt County through Tuesday
morning. All areas should clear out for Tuesday afternoon though,
with high pressure continuing to build in, with brisk onshore and
upvalley winds once again. Expect gusts easily 20 to 30 mph along
exposed portions of the coast the next couple of afternoons,
especially from around Cape Mendocino southward.

Another cold upper trough and area of low pressure will spin
toward British Columbia and Washington on Wednesday, sending
a cold front southward to attempt to drop into northwest
California. It will struggle to do so as high pressure holds firm
along the California coast. There is perhaps a 30 to 50 percent
chance for a few hundredths of an inch south of the Oregon
border, and only a chance for a little drizzle as far south as
Humboldt Bay. That front will act to increase clouds along the
coast on Wednesday, and onshore breezes that afternoon should be
less stout compared to every other day of the week ahead. That
trough will act to shift the main Gulf of Alaska low at least
temporarily southeastward across the Pacific Northwest to the
Rockies late this week. The bulk of the associated cold air will
stay to our north, but it will still cool down temperatures
inland substantially on Thursday. An increasingly dry airmass may
also promote good radiational cooling Thursday night, with perhaps
some frost in some northern interior valleys Friday morning. Otherwise
expect plentiful sunshine with breezy afternoons and evenings
from Thursday into the weekend, as high pressure builds northward
along the West Coast. High temperature will rebound from Friday
into the weekend, with 80s likely for all interior valleys. /AAD


.AVIATION...A widespread and deeper marine layer has developed
across NW California and pushed well inland this morning. The
McKinleyville profiler indicates the marine layer depth is around
5000 feet, while the Bodega Bay profiler indicates it is around 2000
feet. As a result, low clouds covered almost entirely Del Norte and
Humboldt counties, as well a significant portion of Mendocino
County. Stratus will continue pushing inland and reach UKI during
the next few hours to bring it MVFR ceilings through mid morning,
then prevailing VFR conditions. Meanwhile, LIFR conditions have
been impacting the coastal terminals (KACV and KCEC). Otherwise, a
cold front approaching from offshore will destabilize the marine
layer and conditions will become variable at the coastal
terminals. This will favor drizzle through mid/late morning.
Expect MVFR to VFR conditions at the coastal terminal this
afternoon in the wake of the front. Breezy northerly winds with
occasional gusty winds from 15 to 25 kt are expected to develop
this afternoon through this evening at KACV and KUKI, and
persisting through late tonight at KCEC.


.MARINE...Northerly winds will be in the increase across the area
throughout the day today, reaching advisory criteria in the
southern waters by mid morning and for the northern waters late this
afternoon. Look for the strongest winds S of Cape Mendocino where a
narrow portion of gale force gusts will be possible on Tuesday as a
surface ridge builds behind the next frontal system. Winds diminish
on Wednesday and southerly winds develops N of Cape Mendocino as an
upper level trough and associated frontal system moves through,
before quickly shift to north and strengthen Thursday and Friday as
a high pressure build in and tight the pressure gradient. As result,
gales force winds gust will be possible across the outer waters on

Seas around 5 feet are expected through this morning. A short period
NW swell will build today and Tuesday, peaking by early Tuesday
evening to around 7 to 9 feet. Also, a small long-period S swell
will moves across the waters Tuesday evening through Thursday


     Small Craft Advisory from 5 PM this afternoon to 9 PM PDT
     Tuesday for PZZ450.

     Small Craft Advisory from 3 PM this afternoon to 9 PM PDT
     Tuesday for PZZ470.

     Small Craft Advisory from 9 AM this morning to 9 AM PDT
     Wednesday for PZZ455-475.



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