Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Eureka California
408 am PST sun Mar 1 2015
Synopsis...dry conditions are expected today ahead of the next
approaching weak system. There will be a slight chance for showers
late Sunday night through Monday as an upper level system slides
down the West Coast. High pressure will build over the West Coast
Tuesday through the weekend resulting in a gradual warming trend
and dry conditions.
Discussion...an upper level low has moved south of the region
leaving northwest California under generally sunny skies and cool
temperatures. Some areas have fallen into the 20s and
30s...particularly across the interior...while locations where wind
has remain elevated and/or near the immediate coast remain in the
40s. Still expecting sheltered coastal locations to settle into
the middle 30s this morning so have opted to keep the frost
advisories in effect even though frost may not be as widespread as
A deep trough across the interior west will allow another upper
level shortwave to slide down the West Coast tonight through Monday.
This shortwave will bring a brief chance for showers across
northwest California and increased cloud cover. At this time it
looks like the best chance for some light shower activity will be
near the immediate coast late tonight/early Monday morning and
then over the mountains of southern Trinity and eastern Mendocino
counties Monday afternoon. There may be just enough instability to
allow an isolated thunderstorm to form in the afternoon/early
afternoon hours if showers form at all.
Currently not anticipating widespread frost formation tonight into
Monday morning considering the increasing cloud cover in our
currently active growing season zones. However...clouds may not
reach Mendocino County fast enough to keep temperatures from falling
into the middle 30s and a frost advisory may be required. Will allow
the day shift to take another look at it today.
The passing shortwave will also usher in another shot of cooler air
over northwest California for Monday night. A near repeat of
Saturday night/Sunday morning may be in store...though boundary
layer relative humidity will be a little higher possibly resulting
in less potential radiational cooling due to some low clouds and
higher dewpoints. Still...opted to decrease temperatures across
the region closer to the GFS-British Columbia guidance Monday night considering
the anticipated arrival of cooler air.
A gradual warming trend is expected for the rest of the week into
next weekend as upper level ridging builds over the West Coast.
High temperatures may approach the 70s once again in Mendocino
County late in the week with 60s in other valley locations across
northwest California. Rpa
Aviation...VFR will prevail across most of northern California
today as weak ridging over the region will result in dry weather.
Low level moisture will increase ahead of another shortwave trough
later tonight through Monday morning. This will increase cloud
coverage over northwest California yet ceilings should remain VFR through
12z Monday. However, patchy valley fog may develop late tonight
across interior Mendocino and Trinity counties. /Kml
Marine...winds will ease and seas will subside briefly today as the
passing low pressure system allows the coastal pressure gradient to
relax. Near shore buoy observations have been indicating a trend of
the seas gradually subsiding through the early morning hours. As a
result the gale and hazardous seas warnings were allowed to expire
this morning leaving small craft advisories in place. The inner
waters should fall below advisory criteria later today but I
wouldn't be surprised if the sea state remains marginal through the
late morning. This lull will remain short lived as another system
impacts northern California bringing near gale conditions to the
outer waters on Monday. Warnings may be needed but will hold off on
issuing at this point in time. Also in the mix will be a building
southerly swell originating from a southern hemisphere storm system.
There remains a bit of uncertainty regarding its impact, however,
instinct is saying that models may be over doing it especially for
areas north of Cape Mendocino. Never the less, south facing beaches
and anchorages may notice its presence by middle to late week but
impacts should remain minimal. Otherwise fresh northerly winds and
steep seas will persist through middle-week before a ridge of high
pressure builds over the western United States. This will allow the
winds and seas to settle late in the week. /Kml
frost advisory until 9 am PST this morning for caz001-002.
Freeze warning until 9 am PST this morning for caz076.
Northwest California coastal waters...
Small Craft Advisory until 9 am PST this morning for pzz455.
Small Craft Advisory until 9 am PST this morning for pzz410-450.
Small Craft Advisory until 3 am PST Wednesday for pzz470-475.
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