Area Forecast Discussion
Issued by NWS Eureka, CA

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886
FXUS66 KEKA 272120
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
220 PM PDT Thu Apr 27 2017

.SYNOPSIS...Building high pressure off the west coast will bring
dry weather to the coast and warmer temperatures to the interior.
Breezy northerly winds will be observed along the coast during
the afternoon and early evening periods. The drier weather is
expected to persist into next week.

&&

.DISCUSSION...Have made few changes to the existing forecast
package. Mostly mid-level cloudiness is heading toward the coast
at the present time with a bit of low and high cloudiness mixed
in. Some cumulus is noted over mainly the mountains of N Trinity,
NE Humboldt, and E Del Norte counties due to residual low-level
moisture and daytime instability. A shower or two are possible
over E Del Norte county into the early evening hours. The land-
based low cloudiness should thin overnight, but some valley low
cloud and fog development is likely. Have forecast some interior
patchy frost below 3000 foot elevations, but uncertainty is high
due to valley and mid-level clouds, potential fog development,
and areal coverage of colder temperatures. The evening shift will
continue to monitor trends for possible shorter fused frost
advisory issuance. There is the potential for some patchy interior
frost again Friday night, but uncertainty is again high.

An upper level ridge over the E Pacific will build and shift
slowly E into next week, keeping mostly dry conditions across the
area. A weakening front will approach the OR coast on Saturday
night and Sunday. Bumped PoPs a bit during this time frame over
the extreme N, but have kept them silent (<10%). Also added
isolated thunder for the extreme E portion of the area for next
Thursday due to increased instability parameters and the
possibility of a weakening upper ridge. /SEC

&&

.AVIATION...Widespread mid-high clouds dominated area skies today
as high pressure began building over the region...therefore
producing VFR conditions and breezy northwest-northerly winds
today. Drying and warming will generally result from the building
upper level ridge and surface high. However, guidance (due to
some residual low level moisture) suggests a few pockets of
morning clouds/fog briefly developing locally at the coast and a
few coastal valleys. /TA

&&

.MARINE...Northerlies will prevail through the forecast period as
the East Pacific High establishes itself over the area. The
northerly pressure gradient off the NW California coast will be
moderately tight through the weekend. Winds will be around 10 to 20
kt with gusts to 30 kt. Winds will be enhanced Friday night as the
pressure gradient tightens. Occasional wind gusts may get to 35 kt,
especially for the outer waters. The northerly winds will persist
through next week as the east Pacific high is not going anywhere.

We have 3 different wave groups. First is the long period southerly
swell, and it is combined with the mid period westerly swell. The
last wave group is the north wind driven short period wave. The wave
height for this wave group is around 8 feet with wave period of
about 8 seconds. All 3 wave groups are expected to continue into
next week.

Small craft advisory is in effect for all waters through Friday
night. The small craft advisory for the southern outside water will
continue through middle of next week. /RL

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory from 6 PM this evening to 3 AM Saturday
     for PZZ450.
     Small Craft Advisory from 6 PM this evening to 9 AM Saturday
     for PZZ470.
     Small Craft Advisory until 3 AM Saturday for PZZ455.
     Small Craft Advisory until 9 PM Wednesday for PZZ475.

$$

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