Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Eureka California
348 PM PDT Friday Aug 22 2014
Synopsis...high pressure offshore will maintain dry weather
conditions through the weekend. Parts of the coast will continue
to see low clouds and fog each night and morning
Discussion...high pressure at the surface will build into
the Pacific northwest tonight in the wake of a short-wave trough. A
thermal trough will also form near the northern California
coast tonight in response to the building ridge. This pressure
pattern will produce moderate NE to east winds across mainly the
higher elevations of the northern zones. Nam12 x-section across
del Norte County has NE winds ramping up to 20-30 miles per hour tonight
through Sat morning. Granted the gusty northeast and east winds
will be confined to the exposed ridges with most of the lower
elevations and valleys likely seeing little or no winds. A
headline has been added to the fire weather forecast to call
attention to this threat. The rh's are forecast to stay above
critical values tonight. Smoke from the Happy Camp fire will
likely get transported westward into del Norte County and NE
Humboldt counties this weekend. There may even be some smoke
transport out to the coast. At the moment it is hard to tell how
thick or opaque the smoke will be and at what level it will be
concentrated. I increased the patchy smoke coverage in the
forecast. This may need to be increased.
Stratus has almost completely dissipated north of the cape this
afternoon. New stratus may develop around eka and the Eel Delta as
winds decouple. South of the cape stratus has already formed near
the Mendocino coast where the offshore flow was not present.
Mixing on Saturday should be sufficient to clear out most of the
stratus by afternoon. However coastal stratus and fog will likely
regenerate each night and morning...especially around eka and
south of cape mendo. The offshore flow looks to decrease Sunday
night and Monday morning as another upper trough drops into the
Pacific northwest. Gradients should go onshore with widespread stratus more
likely north of cape mendo.
Going into next week the models have been fairly consistent showing
warming aloft and higher temperatures through middle week. The latest
GFS and European model (ecmwf) indicate 500mb heights above 588dm and 850mb temperatures
near 25c. With light offshore flow on Tuesday...temperatures should
increase into the triple digits. The warm up probably will not
last through the end of the week as the models continue to indicate
the ridge flattening out by Friday as another trough approaches
the region. One thing that will need to be watched is moisture
from the tropics being entrained into the trough. The GFS is most
likely overblown on the 2-4 inches of rain next weekend. Those
rain amounts would be historic and record shattering for the last
weekend of August.
Aviation...VFR to IFR conditions and light to moderate winds will
prevail at kcec and kacv this afternoon. The lower conditions are
due to reduced ceilings. Stratus will move into coastal areas late
this evening and overnight reducing ceilings to IFR conditions at
kcec and kacv. Patchy fog will also reduce visibilities at kcec and
kacv early Saturday morning. Light winds to calm conditions will occur
overnight at kcec and kacv. VFR conditions and light winds to calm
conditions will continue at kuki through Saturday.
Marine...the winds and short period seas will increase tonight and
this weekend as a high pressure ridge offshore strengthens and
interacts with a strengthening inland thermal low pressure trough
tightening the pressure gradient. The pressure gradient will relax the
middle of next week allowing the winds and seas to diminish. The
winds and seas will be higher across the outer waters. A long period
southerly swell will persist through this weekend.
Northwest California coastal waters...
Small Craft Advisory until 3 am PDT Monday pzz470.
Small Craft Advisory until 3 am PDT Monday pzz475.
Visit US at http://www.Weather.Gov/Eureka
Follow US on facebook and twitter at: