Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 172152
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
252 PM PDT Thu Aug 17 2017

.SYNOPSIS...High pressure will maintain hot weather conditions
for the interior through the weekend. Temperatures will moderate
early to mid next week.


&&

.DISCUSSION...
Upper level ridging remains in place over Northwest California
resulting in warm and dry conditions across the region. The marine
layer has become quite compact today with strong subsidence along
the coast. The depth of the marine layer should remain fairly
consistent for the next few days as warm air remains aloft and the
marine inversion staying strong. High temperatures at the coast will
generally remain in the 60s while interior areas warm into the 90s
and near 100 degrees.

The only other concerns through the weekend will be offshore flow in
northern Humboldt and Del Norte counties and strong north winds over
the coastal waters that will bring gusty winds to the immediate
coastline. This offshore flow will continue to bring dry air to the
Humboldt and Del Norte coasts and warm conditions to the northern
Del Norte coastline. Additionally, numerous fires in Siskiyou County
and southern Oregon are spreading smoke over the region. This will
likely persist through at least Sunday morning.

Thickness values will begin to decrease late in the weekend as an
upper trough approaches the area. Temperatures will likely level out
or slightly fall as marine air intrusions extend farther inland.
This trough will then become a cutoff low to the west of central
California. Southeasterly flow on the east side of this low will
move moisture back north and model guidance indicates a chance for
convection over the interior mountains by Tuesday afternoon and
slight chances even by Monday. Precipitable water in the GFS is
around 0.75-1.00", indicating that storms will once again be wet.
However this hasn`t been a problem lately in starting wildfires. See
the fire weather discussion below for more information about fire
weather concerns.

The increase in moisture and cloud cover may bring a few degrees of
cooling to the interior for early next week, but a much more
substantial trough will approach the area mid next week likely
allowing temperatures to fall back to near normal. /RPA

&&

.AVIATION...
Marines clouds continued across the North Coast areas through
morning with very little penetration into adjacent coastal
river valleys. Also, smoke continued over portions of Del Norte
and Humboldt Counties today. Some ash was seen across several
Humboldt locales from EKA to ACV.

Del Norte experienced late evening MVFR-IFR conditions before
clearing out in the early morning into afternoon...most likely due
to sufficient offshore flow.

Humboldt County was VFR before briefly drooping to near "rock
bottom" (LIFR)...then clearing out this morning. With somewhat
breezy SW winds, a strange spaghetti looking formation of MVFR
stratus rolled back across the ACV coast shortly after noonday and
lasted about 2 hours. Will watch ACV as a southerly surge has
already pushed around Cape Mendocino. Right now the offshore
component may not inhibit the inflow of low clouds/fog into the
terminal.

Mendocino coast continued to be saturated with the marine
clouds. High pressure seems to have slightly compressed the layer
from previous days.

Interior mountain and valley areas will remain VFR, although smoke
layers aloft will stretch over some areas...especially in the
northern reaches.


&&

.MARINE...
The northerly winds have materialized as expected with bouy 27
gusting to 29 kts this afternoon. The current wind pattern will
continue through the weekend as high pressure builds over the
eastern Pacific and a thermal trough strengthens over California.
The main area of strongest winds will persist over zone PZZ470
(northern outer waters) while the other areas see moderate to
fresh breeze winds. Subsequently, steep seas have been building
with the largest waves occurring over the outer waters this
weekend.

&&

.FIRE WEATHER...
Light to moderate offshore flow will persist across the upper
elevations of zones 203, 204 and 211 for the next several nights
and mornings. There will be subtle changes each night/morning, but
the overall surface flow pattern changes very little going into
this weekend. The bottom line, hot and dry through the weekend.

The focus of attention for Friday looks to occur over the extreme
east side of the CWA around the alps and yolla bolla spine.
Soundings and profiles indicate the potential for cumulus cloud
build ups with the heating of the day but little chances of any
thunderstorm development.

Next week is looking much more favorable for storms if the models
are correct. The GFS continues to show a cut-off low forming off the
central California coast early next week. The GFS continues to
indicate southeasterly flow aloft as well as instability on Monday
and Tuesday. We may be in store for isolated wet storms on Monday
and again on Tuesday, primarily in zones 283 and 277. Confidence is
by no means high at this time due to the variability in the model
data that far out.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 9 PM PDT Sunday for PZZ450-475.

     Gale Warning until 9 PM PDT Sunday for PZZ470.

&&

$$

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