Scientific Forecaster Discussion
fxus66 keka 231059
Area forecast discussion
National Weather Service Eureka California
359 am PDT Wed Aug 23 2017
Synopsis...an upper trough will moderate interior temperatures
through most of the week. Warmer weather conditions are expected
for the weekend as high pressure builds over the area. Coastal
locations will continue to see the usual dose of low clouds and
fog through the week before the marine layer decreases.
Discussion...the upper level trough is approaching the area this
morning. This is starting to push the upper level low off
Southern California that brought the thunderstorms off to the east. This
has ended the thunderstorm threat for northwest California bringing .
This upper level trough is bringing a dry cold front to the area.
Ahead of the front today the immediate coast is expected to only
see a few breaks in the clouds. Inland areas will see high
temperatures be similar to yesterday.
Tonight the front will move through. The main impact is expected
to be some drizzle at the coast and possibly a few gusty north
winds over the ridges. Thursday the cooler air aloft should weak
the inversion and this should help lift the marine layer and
break it up. This is expected to bring some clearing to the coast
by late morning or early afternoon. Areas just inland from the
coast may continue to see some clouds. Inland temperatures will be
cool 5 to 10 degrees with the near coastal areas possibly cooling
a bit more as the cooler air mass moves in.
This cooling will be shortlived as high pressure starts to build
into the area on Friday. Temperatures will continue to warm for
the weekend. The marine layer is expected to shrink back towards
the coast for the weekend. This will likely lead to some afternoon
clearing, but offshore flow is weak at best so confidence is low
on this. Sunday a weak short wave moves by to the west. This may
weaken the winds enough to allow a flow reversal at keep stratus
in place at the coast for much of the afternoon south of Cape
Early next week the ridge starts to push a bit off to the east.
This may be enough increase the depth of the marine layer and
allow the stratus to be a bit more persistent. Inland
temperatures will generally remain warm although the near coastal
and coastal areas may see some cooling. Mkk
Aviation...stratus continues to hug the Redwood and Mendocino
coasts, and this will likely continue through the day based on
little change in the synoptic pattern. In fact, the latest
profiler sounding out of McKinleyville continues to show the
marine layer depth holding around 2000 feet. With an onshore flow
continuing kcec will likely remain in IFR conditions through the
forecast period, with ceilings struggling to climb above 500 feet
most of the time.
Farther south at kacv, a little improvement can be expected here.
However, ceilings at this terminal should remain below 1000 feet. In
either case, if we can get some high-level cirrus to retrograde
towards the coast from any thunderstorms that develop near the
Trinity Alps, this may allow for some occasional breaks in the
overcast with a temporary rise in ceilings, but, this is looking on
the very optimistic side of things.
For kuki, look for VFR conditions to prevail, with just a few high
clouds crossing the sky from time to time. Winds will remain light
Marine...the latest buoy observations early this morning
continue to show rather benign sea conditions, with seas running
in the 3 to 4 feet range. Unfortunately, no wave heights were
reported with a recent voluntary ship observation in the outer
waters, and with the buoys generally in the inner waters (aside
from buoy 13 which is roughly 15 miles offshore), thus the waves
are likely a foot or two higher across the western half of zones
470/475. In either case, small craft conditions have occasionally
been observed, and with the pressure gradient tightening due to
increasing high pressure strength further west/southwest, will
maintain the current headlines as they are for these two zones.
Over the next 24 hours, northerly winds will increase due to
increased baroclinicity between the building surface high to our
west and warmer conditions over the coast/inland areas of
northwestern California. This will cause a gradual increase in wind
speeds and wave heights over the next few days. As a result, small
craft advisories have been hoisted for the inner waters as well.
It's not out of the question either that the outer waters may need
to be upgraded to a Gale Warning. However, sustained winds look to
remain just below this threshold, and wind gusts reaching 34 knots
is near the top end of the model guidance. We'll give the models
another run or two before potentially upgrading to a warning. /Pd
Northwest California coastal waters...
Small Craft Advisory until 9 PM PDT Thursday for pzz470-475.
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