Scientific Forecaster Discussion
fxus66 keka 301029
Area forecast discussion
National Weather Service Eureka California
329 am PDT sun Apr 30 2017
Synopsis...generally mild and dry conditions are forecast to
prevail across the region through Wednesday. Thereafter, cooler
temperatures and increasing rain chances appear possible during
the latter portions of the upcoming week.
Discussion...the previous forecast package is generally on track
through Thursday. Light rain or drizzle is expected Sunday
morning over Humboldt and del norte counties as a frontal boundary
weakens over the area. A similar scenario repeats Monday
night...with very light rain possible over del Norte County. In
addition, a strengthening marine boundary layer inversion will aid
in stratus over the Pacific...as well as adjacent coastal areas
north of Cape Mendocino. Otherwise, a midlevel ridge is forecast
to shift east to the Great Basin by Thursday. Low-level
temperatures will warm as this takes place, with many interior
valleys experiencing highs in the 80s Wednesday and Thursday.
Deterministic and ensemble model guidance then depict an
amplified upper trough digging south toward northwestern California Friday into
Sunday. The 00z GFS and European model (ecmwf) showed good agreement with the
evolution of this trough...however, the 06z run of the GFS has
backed off on its southward extent. Thus, forecast uncertainty is
relatively high beyond Thursday/day 5.
Aviation...stratus just offshore the coast will push into the
coastal terminals this morning. IFR ceilings are expected with
perhaps reduced vsbys in drizzle and mist. Conditions should
improve this afternoon as mixing increases, however MVFR ceilings
may linger into the afternoon hours. Coastal low clouds will
probably redevelop by mid evening as winds decouple. VFR will
continue to prevail through the period at kuki, though some
patches of low cloud will be possible along the Mendocino coast.
Marine...light to moderate northerlies will prevail through the
forecast period. Scatterometer pass from yesterday indicated winds
from 20 to 25 kt over the waters south of cape mendo. The
advisory for small craft appears to be on track. North of Cape
Mendocino, winds have been lighter, however a brief northerly
surge will develop today after a front pushes across the Pacific
northwest. North of cape mendo, winds will be marginal for an
advisory today with mostly gusts to 25 kt or so. Seas will
probably take til this evening to become large and steep again.
Northerly winds will ease north of the cape on Monday as another
front approaches the West Coast and disrupts the offshore ridge.
South of cape mendo, north winds will remain in the 15 to 25kt
range to warrant an advisory through mid week.
Northwest California coastal waters...Small Craft Advisory from 2
PM this afternoon to 5 am PDT Monday for pzz455-470.
Small Craft Advisory until 5 am PDT Wednesday for pzz475.
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