Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 280022
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
522 PM PDT Mon Mar 27 2017

.SYNOPSIS...High pressure will build briefly this afternoon
bringing drier weather conditions through Tuesday. Another
rain producing system will arrive late Wednesday followed by
a dry and warmer period toward the weekend.

&&

.UPDATE...Did a quick update to the forecast to add a frost
advisory to northeast Mendocino county. Clear skies and calm winds
will likely allow frost to form tonight. MKK

&&

.PREV DISCUSSION... /issued 353 PM PDT Mon Mar 27 2017/

SYNOPSIS...High pressure will build briefly this afternoon
bringing drier weather conditions through Tuesday. Another
rain producing system will arrive late Wednesday followed by
a dry and warmer period toward the weekend.

DISCUSSION...A drier northwesterly has set up promoting sunshine
and much drier air. Responsible for this is some upper level
ridging and stable air which will build toward the coast
throughout the remainder of this afternoon bringing a welcome end
to the shower activity. Cooler air will settle over the area
tonight and a Frost Advisory has been issued for the interior
valleys of Mendocino county. Stronger subsidence and light
offshore winds should provide steady drying through early Tuesday.
A frost advisory will need to be considered with temperatures
expected to fall to near 34F- 36F across those valleys and
possibly lower locally. Except for morning frost, Tuesday is
shaping up to be a fine day after the morning low clouds and fog
burn off in the interior valleys. Dry conditions should last
through the morning hours on Wednesday as surface ridging remains
over the area. Another front will approach the West Coast Wed
afternoon. The models have slowed down the warm front slightly,
but still have the cold front moving through Wednesday night when
most of the rain is expected. Ridging aloft and robust northerly
flow at the surface will build after the passage of a mid level
shortwave trough on Thu. With brisk northerly winds offshore,
coastal areas will probably get fairly windy each afternoon,
especially on Friday. Dry weather will likely hold into the
weekend, however the GFS and ECMWF continue to forecast the ridge
to flatten out toward the end of the weekend in response to
another shortwave trough. Some rain or showers will certainly be
possible Sun or Mon. For now will keep the forecast dry with only
a slight chance of rain. We may need to beef up the rain chances
if the models continue on their present course. JT/DB

AVIATION...Showers were diminishing through the day. By the
afternoon, we are left with shallow convective clouds over the hills
and mountains, giving us VFR conditions. Do expect these convective
clouds to dissipate after sunset as we lose daytime heating. Do
expect northerly low level winds to develop over Crescent City and
Humboldt Counties and this will bring in drier air into the area.
The dry air advection will limit the fog and low cloud potential
overnight at those airports. For Ukiah airport, there won`t be as
much dry air advection. Thus, put in some low clouds and reduced
visibilities for potential fog and low clouds formation. Tomorrow
should be a mostly sunny day across NW California. /RCL

MARINE...Westerly swells impacting NW California through middle of
the week. Northerly winds will prevail across NW California waters.
Winds will be increasing to advisory level starting on Thursday.

Through this afternoon, area buoys have been reporting northwest
wind around 10 to 15 kt. Do expect the northwest wind to continue
through tomorrow  into Wednesday as a high pressure builds over the
Eastern Pacific Ocean and a thermal trough sets up shop over
Central Valley. On Thursday, the high pressure will push east and
tightens the pressure gradient off the coast of NW California.
The northerly winds will pick up to small craft level starting on
Thursday. Looks like the strong northerlies will persist through
the start of the weekend.

Seas-wise, it is pretty excited for the next few days. We have a
decaying westerly mid-period wave group, while a notable westerly
swell move into the waters. This westerly swell will start off at
around 20 seconds. The period of this swell will shorten with time,
down to 12 to 14 seconds by Tuesday and Wednesday. With wave height
of around 10 feet, this warrant a small craft advisory due to seas.
Do have the small craft in effect through Wednesday.

Minimal changes to the previous forecast package were made, as the
forecast is still on track from the previous version.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory from 1 AM to 9 AM PDT Tuesday for CAZ110-111-113.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 3 PM PDT Wednesday for PZZ450-455-470-
     475.

&&

$$

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