Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 202238
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
338 PM PDT Sun Aug 20 2017

.SYNOPSIS...Northeasterly winds will continue to transport smoke
across the Redwood Coast through Monday. Otherwise, thunderstorms
will be possible over portions of Trinity and northeastern
Mendocino Counties during the afternoon and evening hours of
Monday, Tuesday, and Wednesday.

&&

.DISCUSSION...An offshore directed surface pressure gradient
located over far NWRN CA is forecast to completely dissipate by
Monday afternoon, with onshore winds developing in its wake. This
should aid in gradually cutting off the Redwood Coast from the
steady stream of thick inland wildfire smoke spreading SSW from
Siskiyou, Curry, and far eastern Del Norte Counties.

Otherwise, a weak upper low is evolving offshore from SRN CA.
Model guidance indicates that moisture, along with cooler midlevel
temperatures, will spread north-northwest from the upper low
through midweek. This will yield an environment favorable for
isolated thunderstorms over the Yolla Bolly Mountains during
Monday afternoon. Thereafter, thunderstorm coverage will increase
Tuesday afternoon/evening from northeastern Mendocino County
north across much of Trinity County. Thunderstorm potential will
become more marginal during Wednesday as drier midlevel westerlies
spread across the region.

After Wednesday, an upper ridge is forecast to amplify over the
WRN CONUS, which will favor moderating temperatures across the
interior.

&&

.AVIATION...Wildfire smoke continues to wreak havoc with the
coastal terminals today with persistent MVFR to occasional IFR
ceilings and visibilities due to this smoke. This pattern will
persist tonight and into tomorrow before a gradual wind shift
occurs that should help to mitigate the smoke coverage across the
region.

Tonight marine stratus should come back to KACV dropping
conditions to IFR sometime around midnight or possibly sooner.
With strong winds still at KCEC am not expecting much stratus to
make it into the terminal until early in the morning however if
winds cease a little earlier than expected this stratus may
materialize sooner. Either way stratus/smoke should keep KACV and
KCEC in at least MVFR conditions through tomorrow with periods of
IFR possible. KUKI did get stratus and fog early this morning and
with a similarly deep marine layer and southerly winds this
possibility could exist for tomorrow morning as well. If the
stratus does make it in to KUKI I would expect it to burn off by
late morning leaving the terminal in VFR conditions for the rest
of the day. /WCI

&&

.MARINE...Gale conditions will continue to occur across the outer
waters through tomorrow morning. Very large and steep seas will
also persist through tomorrow morning and then gradually begin to
decrease through the early part of the week. The inner waters will
have a small craft advisory in effect through early tomorrow
morning as well for winds and large steep waves. In addition, a
hazardous seas warning is in effect for the northern inner waters
till later tonight for very large and steep seas. Tomorrow
afternoon conditions will improve for the southern inner waters
however strong winds may still be possible near Cape Mendocino
however the spatial coverage is too small to continue to the small
craft advisory for that zone. By late Tuesday conditions across
all marine zones will calm with smaller seas and weaker winds.
Conditions will start to deteriorate yet again Friday and persist
through the weekend. /WCI

&&

.FIRE WEATHER...Occasional gusts out of the northeast from 20-30
mph are forecast to diminish this evening. Otherwise,
thunderstorms will be possible during the afternoon/evening hours
of Monday, Tuesday, and Wednesday over portions of Trinity and
northeastern Mendocino Counties. Slow storm motions will favor
wetting rainfall beneath individual storms. However, warmer and
drier conditions during late week could allow holdover fires to
continue to burn and eventually strengthen.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
     11 AM PDT Monday for PZZ450.

     Hazardous Seas Warning until 11 PM PDT this evening for PZZ450.

     Gale Warning until 11 AM PDT Monday for PZZ470-475.

     Small Craft Advisory until 5 AM PDT Monday for PZZ455.

&&

$$

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