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Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 252349
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
449 PM PDT Thu May 25 2017

.SYNOPSIS...An upper-level trough passing by to our northeast
will keep temperatures a few degrees below seasonal values through
Saturday morning, before ridging aloft builds across the region
through at least the first half of next week. This ridge will also
bring warmer temperatures to the region, especially across the
interior.

.UPDATE...Stratus coverage over Mendocino county has remained
slightly more widespread than previously expected so have adjusted
to forecast to start out with more clouds. In Humboldt county
expect this evening clouds wills start to fill in faster than
previously expected. Tomorrow clouds may be slow to clear out due
to the deep marine so have adjusted them slightly as well. MKK

.PREV DISCUSSION... /issued 240 PM PDT Thu May 25 2017/

DISCUSSION... SHORT TERM... (Tonight through Friday night)

Look for a repeat performance of our weather tonight, as stratus
will build inland through the some of the interior valleys and along
the coast. Here, these clouds will help insulate the ground, keeping
overnight temperatures a little warmer. Otherwise, look for
temperatures to fall into the 40s tonight, with the colder readings
found across the interior east of the coastal range. Clouds will
gradually burn off by the late morning/early afternoon hours where
stratus does develop.

Temperatures on Friday afternoon will be similar to today along the
coast. However, with a trough axis taking its time to cross the
forecast area, highs across the interior will be a little cooler
compared to today. More coastal/valley stratus looks to develop
Friday night, in the typically prone areas.

LONG TERM...
(Saturday through Thursday)

Increasing temperatures and mainly dry conditions will be the main
theme for the weekend. The aforementioned trough axis will exit the
area to our east, with ridging aloft building across the region
through the first half of Monday. Increasing heights and warming
temperatures will provide seasonably warm conditions along the
coast, while interior locations warm several degrees, with a few
spots climbing into the 90s by Sunday/Monday.

The forecast become a little more interesting for the latter half of
the weekend into early next week as well concerning convective
potential. The models continue to show precipitation developing
across the Yolla Bollys and near the Trinity Alps on Sunday and
Monday. They do show lifted indices dropping into the -3 to -6
range with MLCAPEs of 750 to 1500 J/kg. Even so, I`m having trouble
buying into this as ridging will be prevalent, with no vort maxes
seen anywhere nearby. With that in mind, it does look like
convective temperatures could be approached or breached, but again,
confidence in this occurring isn`t all that high. So for now, the
forecast was largely unchanged.

The tail end of a trough passing by to our north may increase rain
chances for locations north of highway 299 if the GFS solution
verifies. Otherwise, the net effect from the trough will be some
cooling aloft, allowing afternoon highs to drop a few degrees for
the middle to end of the work week. /PD

AVIATION...
Along the coast/near coastal valleys north of Cape Mendocino, marine
clouds gave way to mostly sunny skies earlier than yesterday. A
vibrant northerly flow kept skies clear at the CEC air terminal.
However at ACV and the Humboldt Bay Area, MVFR-IFR conditions
persisted until around noonday with mostly light and variable winds.
Speaking of winds...although the northerly flow will remain somewhat
robust, winds will not be as strong as yesterday. Will keep with
persistence as guidance showing no significant changes. Therefore
marines clouds expected to return to the coast this by late
evening.

Inland: A pronounced marine layer spilled into river valleys
especially in Mendocino where the whole county was inundated with
nearly a 100% blanket of CIGS 010-025. Clouds were fairly slow to
erode, but finally eroded west over the coastal hills/mountains and
into the Anderson Valley as shown on the 1PM VIS Sat Picture. The
marine layer will remain deep enough that stratus will again spill
and spread into the UKI valley including the UKI air terminal
overnight. /TAA

MARINE...
Winds and seas in the coastal waters have been slowly
diminishing today. Winds and seas will continue to subside tonight.
Lighter winds and lower seas are expected for Fri through Sat as
broad low pressure develops over the waters. Light N-NW winds will
return for Sunday and Monday.

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 6 PM PDT this evening for PZZ450-475.

Hazardous Seas Warning until 6 PM PDT this evening for PZZ450-
475.

Gale Warning until 6 PM PDT this evening for PZZ470.

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