Area Forecast Discussion
Issued by NWS Eureka, CA

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505
FXUS66 KEKA 242257
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
357 PM PDT WED AUG 24 2016

.SYNOPSIS...Coastal areas can expect overnight and morning
cloudiness the next few days with some clearing in the afternoons.
Temperatures will continue to be near to slightly above normal
across the interior through Thursday. An upper trough will slide
over the Pacific Northwest late in the week bringing more seasonal
temperatures. Little, if any, rain is expected.

&&

.DISCUSSION...Benign...typical weather conditions can be expected
for the foreseeable future across the region as a weak trough of
low pressure aloft gradually slides overhead. The primary impact
that this will have on area weather will be to gradually lower
inland temperatures from slightly above normal to very near normal
over the weekend and early next week. Meanwhile, this trough may
also help to deepen the marine layer slightly, bringing stratus
and fog slightly farther into coastal valleys and low elevation
hills. An increase in offshore flow may also help to erode
offshore stratus coverage overnight tonight, primarily north of
Cape Mendocino, but not enough to prevent it from moving into most
low-lying coastal plains. Expect a continuation of nocturnal
stratus through the weekend and into next week, including perhaps
some patchy drizzle in places.

Meanwhile, gusty offshore winds and dry air aloft will result in
critical fire weather conditions across the high elevations of Del
Norte and Northern Humboldt counties overnight tonight and
tomorrow morning, and a more detailed discussion of this threat is
included in the fire weather discussion below. /BRC


&&

.AVIATION...Another day of pretty intense coverage of marine
stratus. The morning start off with marine stratus covering the
coastal areas and adjacent river valleys. LIFR conditions were
reported in Crescent City and Arcata airports. Visibilities were
as low as one quarter of a mile at times this morning, with
ceiling as low as 200 feet. By this afternoon, we still haven`t
broken out of the low overcast in Crescent City and Arcata
airports, as we are still stuck underneath a overcast deck of 300
feet with improved visibilities. Do not expect the two airports to
break out, as we are going to be running out of peak daytime
heating soon. Do expect the LIFR conditions to return from early
this evening and continue into tomorrow morning. /RCL

&&

.MARINE...Winds and seas will continue to diminish overnight into
Thursday and continue into Thursday evening as high pressure
continues to shift away from the area. Early Friday, a trough of
low pressure will take shape off the NW California coast, and this
will allow southerly winds to develop along the coast. As the
southerly winds go around Cape Mendocino, there will be some
acceleration factor to the wind. Right now expecting 10 to 20 kt
south wind with higher gusts near Cape Mendocino on Friday. The
south wind will then continue from Friday night through the
weekend. Looks like by early next week, the high pressure will
rebuild over East Pacific, and this will allow the northerly to
return to NW California coast.

Since this morning, buoys have been reporting wave heights of 4 to 5
ft. For the outside waters, do expect 6 to 7 ft of wave height with
7 to 8 seconds wave period. The waves will be marginally steep to
warrant a small craft advisory. Seas will subside to below small
craft level starting Thursday morning. Seas will remain fairly low
through the weekend into early next week.

Little changes were made to refresh the forecast package. Forecast
confidence is about average. Models of choice includes GFS and GEM.
/RCL

&&

.FIRE WEATHER...A Red Flag Warning has been issued for fire
weather zones 203 and 204 from 11 pm tonight until 11 am tomorrow
morning. This includes interior areas of Del Norte...far northeast
Humboldt...and far western Siskiyou counties...and applies
specifically to elevations above 2500 feet.

The primary motivator for the issuance of this Red Flag Warning
is the expected increase of gusty easterly offshore winds, which
will occur in concert with dry air aloft and poor overnight RH
recoveries across mid and upper slopes. RH recoveries have been
poor across many interior ridges throughout the region the past
few days. However, for the most part wind speeds have remained
light aside from a few isolated areas. Tonight, though, it appears
that offshore winds will be a bit stronger across the high terrain
of Del Norte and far northern Humboldt counties, which tend to be
prone to these dry nocturnal offshore winds. As a result, the mid
and upper slopes of these areas will likely see a period of
critical fire weather conditions late tonight through tomorrow
morning. Tomorrow afternoon, warm temperatures and low minimum
afternoon humidity values will return; however, wind speeds will
likely decrease as they turn to a more onshore direction. This
will not likely be the case farther north across southwest Oregon,
where gusty offshore winds will likely continue through the day.
Farther south across the remainder of Northwest California,
moderate to poor RH recoveries can still be expected across upper
slopes, but lower wind speeds will preclude a Red Flag issuance at
this time. Some gusty offshore winds will also be possible along
the coastal hills of Humboldt and Del Norte County (i.e. the Bald
Hills, Kneeland, etc.) as well, but overnight recoveries in these
lower elevation hills are expected to be slightly better than
farther to the northeast where the RFW has been issued. /BRC

&&

.EKA Watches/Warnings/Advisories...
CA...Red Flag Warning from 11 PM this evening to 11 AM PDT Thursday
     for CAZ203-204.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 9 AM PDT Thursday for PZZ470-475.

&&

$$

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