Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 192219

National Weather Service Eureka CA
319 PM PDT Sat Aug 19 2017

.SYNOPSIS...Northeasterly winds will continue to transport smoke
across the Redwood Coast through early next week. Otherwise, above
average temperatures will persist across interior northwest
California through the middle of next week. In addition,
thunderstorms will be possible over portions of Trinity and
northeastern Mendocino Counties during the afternoon and evening
hours of Monday, Tuesday, and Wednesday.


.DISCUSSION...A tight surface pressure gradient will locally be
generated over NWRN CA tonight as high pressure builds SWD over
SRN OR/NCNTRL CA, and a trough of lower pressure sharpens along
the coast. This will yield winds gusting from 20-30 kt across
exposed ridges in Del Norte County, resulting in a critical fire
weather threat (refer to the fire weather discussion below).
Northeasterly winds will also aid in transporting thick (mainly
elevated) smoke from inland wildfires SWD across the Redwood Coast
through at least early next week.

Meanwhile, an upper-level low is forecast to develop in the
vicinity of coastal southern CA. A cooler midlevel airmass will
gradually spread north-northwest from the low, and aid in
destabilizing the environment over Trinity and northeastern
Mendocino Counties Monday through Wednesday. This will will lead
to conditions supportive of thunderstorm development, with the
greatest coverage expected Tuesday afternoon/evening.

Model guidance shows drier conditions and moderating inland
temperatures developing by next weekend as a ridge builds in the
wake of a trough passing E across the PAC NW.


.AVIATION...Dry conditions will persist for the next day as
surface high pressure remains over the eastern Pacific. The
primary meteorological impact today and Sunday will be gusty
northerly coastal winds, particularly at CEC, where the pressure
gradient is tightest between the high over the eastern Pacific and
low pressure over interior California. Some coastal stratus will
redevelop tonight with pockets of LIFR ceilings and visibilities
south of Klamath.

Otherwise, a large non-meteorological impact will be continued
smoke streaming across the region from nearby wildfires bringing
localized MVFR ceilings and reduced visibilities at times. /RPA


.MARINE...A strong gale is developing over the outer waters this
afternoon and will persist through tonight. Very steep seas will
develop in response to the winds, peaking between 14 and 16 feet
in the outer waters. Some of these seas will move into the inner
waters north of Cape Mendocino requiring the issuance of a
Hazardous Seas Warning for the northern inner waters zone. The
seas will gradually subside Sunday into Monday as the winds begin
to decrease and the tightest pressure gradient shifts farther
west/north. Gale warnings in the outer waters will be able to
expire by Monday morning.

A short period of moderated winds and lower seas is in store
early to mid week as an upper low develops off the
central/southern California coast. Some light southerlies will be
possible along the immediate coastline which is not currently
depicted in the forecast.

Stronger northerlies will likely return late in the week as an
upper level ridge re-develops over the west coast. /RPA


.FIRE WEATHER...Northeasterly winds gusting from 20-30 mph are
forecast to occur for elevations above 1500 feet in Del Norte
County through Sunday morning. These winds combined with poor
overnight RH recovery near 20 percent and sufficiently dry fuels
will yield a locally critical fire weather threat. A red flag
warning remains in effect for fire zone 203 (Upper Smith) in
interior Del Norte County from 5pm this afternoon to 8am Sunday
for elevations above 1500 feet. Surrounding the red flag warning,
slightly weaker winds will limit the severity of the fire weather

There is a chance of thunderstorms during the afternoon and
evening hours of Monday, Tuesday, and Wednesday across Trinity and
northeastern Mendocino Counties. These storms are expected to
move very slowly, which will favor wetting rainfall collocated
with lightning.


CA...Red Flag Warning until 8 AM PDT Sunday for CAZ203.

     3 AM PDT Monday for PZZ450-455.

     Hazardous Seas Warning until 9 AM PDT Sunday for PZZ450.

     Gale Warning until 3 AM PDT Monday for PZZ470-475.



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