Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 291000

National Weather Service Eureka CA
300 AM PDT Mon May 29 2017

.SYNOPSIS...Coastal areas will continue to be under the influence
of a stubborn marine layer with cool cloudy conditions. Interior
areas may see isolated thunderstorms develop over the mountains
Monday afternoon...followed by cooler and showery conditions for
the remainder of the week.


.DISCUSSION...A transition of airmasses will begin today
as the upper ridge of high pressure axis moves east of
CA and allows an upper level trough to approach the coast.
The current stubborn marine layer should persist at least one
more day thus another gloomy day is expected for most of the
coastal areas...but some mixing may finally occur on Tuesday. For
interior areas however the approaching trough aloft will provide
a combination of increased low- level moisture and instability,
along with some weak dynamic forcing aloft. This will lead to
increased potential of convection over the interior this
afternoon. Isolated thunderstorms are possible, mainly over
Trinity County but given the southeastern steering flow...any
storms that develop may float westward into eastern Humboldt or
Del Norte counties as well. Even better chances of showers are
expected on Tuesday, but, as mentioned by previous shifts,
instability will be waning during this time frame as cooler air
moves into the area. For now, have continued with just a showery
forecast for Tuesday. A couple of weak surface fronts will
approach the OR coast through mid- week, but these will mainly
serve to increase cloudiness across parts of our County Warning
area. Heights are expected to build over the W coast by late in
the coming week, with decreasing chances of rain and warmer
temperatures. Maximum temperatures may once again rise into the
90s over portions of the interior by next weekend.


.AVIATION...The marine layer will continue to shrink in depth
today as the upper level system offshore moves across the area.
Greatest change in the last 24 hours will come tonight when the back
edge of this system passes over the coast.  Expect coastal sites
will see IFR and MVFR cigs this morning with cigs rising though the
day as the upper system approaches. At times patchy drizzle over the
coast this morning will reduce visibility at these sites. Expect vfr
conditions to continue for inland areas.


.MARINE...North-northwest winds for the most part returned to the
coastal waters today. Northerly winds will be borderline for an
advisory in the waters south of Cape Mendocino today through late
tonight. High resolution models indicate a weak expansion fan
developing downwind of Cape Mendocino by Monday morning. Steep short
period northerly wind waves are expected to build to 5 to 7 ft on
Monday as winds reach 20 to 25 kt. Therefore, a small craft advisory
has been hoisted for the offshore waters south of Cape Mendo.


NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 5 AM PDT Tuesday for PZZ475.



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