Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Francisco Bay area
835 PM PDT Thursday Apr 17 2014

Synopsis...dry conditions will continue through the weekend.
Moderate onshore flow will maintain cool conditions near the
coast...along with areas of night and morning low clouds and fog.
Temperatures for inland areas will mostly remain a little warmer
than normal. A low pressure system will arrive late Monday and
Tuesday...bringing a chance of showers as well as cooler
temperatures through Wednesday.

&&

Discussion...as of 8:35 PM PDT Thursday...an upper level trough
and associated cold front are currently moving through the Pacific northwest
and northern California. Isolated thunderstorms have developed
along the front this evening across far northern California...but
the front is dry at our latitude. This system has produced enough
cooling aloft and low level mixing across our area to mostly mix
out marine layer clouds this evening. Expect areas of low clouds
to develop near the coast late tonight as northwest winds begin
to ease.

Cooling occurred across most of our area today...but temperatures
are expected to rebound slightly beginning tomorrow as shortwave
ridging develops aloft. A shortwave trough will move into the Pacific
northwest on Saturday...but this trough is expected to be too far north
to have an impact on our weather. In fact...very little change is
expected from Friday through Sunday. Daytime temperatures will be
slightly above normal inland and near normal to slightly below
normal at the coast where moderate onshore flow will persist.
Areas of night and morning low clouds will continue...but clouds
will mostly be confined to coastal areas.

Onshore flow will strengthen on Monday as an upper level trough
approaches the West Coast. Temperatures will begin to cool on
Monday and then drop several degrees below normal on Tuesday and
Wednesday as the upper trough moves inland. Shower chances will
begin Monday evening and continue through Wednesday morning...with
the best chance of measurable rainfall expected late Monday night
and Tuesday morning. There may be enough instability on Tuesday
for isolated thunderstorms to develop...mainly across the
northern part of our area. This system will not have a great deal
of moisture with it and rainfall amounts from late Monday through
early Wednesday are expected to be light...generally less than a
tenth of an inch. Dry conditions should return to most areas by
Wednesday afternoon. The medium range models then indicate a
potentially stronger and wetter system arriving by the last
weekend in April.

&&

Aviation...as of 4:35 PM PDT Thursday...a strong north to south
surface pressure gradient is aiding in keeping stratus out of the
San Francisco Bay area this afternoon but is maintaining stratus
in the Monterey and Salinas area. The Fort Ord profiler is showing
that the marine layer has deepened to around 2000 feet...dew
points are also a few degrees warmer than at this time yesterday
as well. With this in mind expect stratus to persist in the
Monterey area and possibly form late tonight in the San Francisco
Bay area.

Vicinity of ksfo...VFR is expected to persist through 0800z at
which point ceilings are expected to develop bkn-ovc015. West winds at
20 knots gusting to 30 knots will decrease to 12 to 15 knots beginning
around 0500z.

Confidence is moderate

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...MVFR ceilings ovc015 are expected to
fall to IFR ovc007 beginning around 0800z. Southwest winds around
10 to 15 knots will persist into the late evening hours.

Confidence is high

&&

Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Small Craft Advisory...San Francisco Bay south of the Bay Bridge until 10 PM

&&

$$

Public forecast: dykema
aviation: Larry

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