Area forecast discussion
National Weather Service Eureka California
403 PM PDT Wednesday may 22 2013
Synopsis...
cool air will continue to flow into northwest California through
Thursday. Interior areas will have another frosty morning on
Thursday. Scattered light showers will be possible north of Point
Saint George and over the higher terrain north of Mendocino County.
&&
Discussion...
a rather potent shortwave rotating around the base of the large cold
upper low spinning over the Pacific northwest has been trying its
best to push clouds and showers into the Redwood coast today.
However with the boundary layer flow being rather diffluent and
drying south of point St George, conditions have been mostly sunny
today. North of the Klamath, including Crescent City, onshore flow
has kept mostly cloudy skies and scattered showers around. Even
there the rainfall has been very light. With the steeper lapse rates
in colder air aloft today, cumulus and towering cumulus has popped up over the
ridges of the north coast interior with a few low-topped showers
there as well. Expect all of this activity to tend to wane heading
through this evening as the passage of the shortwave trough
coincides with the loss of daytime heating.
Lapse rates will progressively lower through Thursday night as the
upper low begins to fill and temperatures warm aloft. However,
enough moisture and instability will linger to allow for isolated to
widely scattered light showers north of Cape Mendocino through
Friday morning as spokes of moisture and energy rotate around the
upper low. One such wave will approach Thursday morning with a
shower or two possibly drifting into Humboldt Bay...otherwise expect
any shower activity to stay north of the Klamath again...or over the
high terrain during the afternoon. Outside of showers and further
south there will be a good deal of sun. The last wave pushing the
Friday morning will only have very shallow moisture to work with in
a relatively stable atmosphere...so this may just end up being a
light early morning drizzle north of Trinidad. Otherwise Friday will
be drier and warmer with plenty of sunshine.
The other forecast challenge in the short-term will be low temperatures
tonight. Issued frost advisory for the inland valleys of Mendocino
County...such as the Anderson Valley...but the immediate coast
should see enough wind or onshore flow to keep temperatures mild
enough to preclude frost. Otherwise the interior can expect
temperatures very similar to last night...if not slightly colder in
Trinity and interior Mendocino. Do not think the Redwood coast zone
will see widespread frost but patches cannot be ruled out in the
colder spots...especially if skies remain mostly clear overnight.
A break in the weather will arrive for Friday and perhaps linger
into Saturday...but another disturbance may bring enough moisture
for isolated showers or mountain thundershowers...especially for
northern interior areas. Baggy troughiness will linger into next
week. Models have converged on a potentially more widespread
rainfall early next week. Kept probability of precipitation high chance to likely later Monday and
Tuesday. Aad
&&
Aviation...VFR conditions and light to moderate winds will continue
at kcec, kacv and kuki through Thursday with the exception that a
few isolated showers may move across kcec and/or kacv at times this
evening through early Thursday. Any showers may temporarily reduce
ceilings to MVFR conditions at kcec or kacv. The winds will become
light to calm overnight tonight.
&&
Marine...the pressure gradient will continue to relax and
subsequently the winds and seas will gradually diminish across the
waters the next few days. Light to moderate winds and moderate seas
will prevail across the waters Friday through early next week.
&&
Eka watches/warnings/advisories...
California...frost advisory from 2 am to 8 am PDT Thursday caz002-003.
Freeze warning from 2 am to 8 am PDT Thursday caz004-076.
Northwest California coastal waters...
Small Craft Advisory until 9 PM PDT this evening pzz455-475.
&&
$$
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