Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Francisco Bay area
437 PM PDT Wednesday Apr 16 2014

Synopsis...dry conditions will continue through the weekend.
Patchy fog and clouds near the coast will become more extensive
Thursday night and Friday as a weak weather system moves onshore.
A stronger low pressure system will arrive late Monday and Tuesday
bringing a threat for showers...colder temperatures...and gusty
winds.

&&

Discussion...as of 3:00 PM PDT Wednesday...outside of a few
higher clouds that are drifting north to south through our cwa,
mostly sunny skies today with a strong north-northwest flow at the surface.
The extra sunshine is helping to boost temperatures today -- in fact
almost all inland spots are at least in the 70s. Coastal locations
are generally in the 60s. The northerly flow is forecast to become
more northwesterly tonight which should help to bring back clouds
to at least coastal spots.

Very quiet weather is on tap through Monday next week as the main
storm track remains well to our north. Only synoptic item of
note is a weak shortwave trough that will move across most of the
West Coast Thursday night. This should help to increase the depth
of the marine layer and cloud cover for overnight hours. Patchy
fog will also be on the increase. By Friday highs will be 5 to 10
degrees cooler than today for most spots. Highs will warm again
for the weekend as heights slightly increase as the system exits.

Tuesday continues to look interesting as a strong, cold system for
this time of year will dive southward toward our County Warning Area. Models continue
to depict 700 mb readings down as cold as 11c with enough moisture
and instability to kick of showers answer possibly a thunderstorm.
Winds will also ramp up especially along the coast and higher
elevation locations. Worth noting that the latest European model (ecmwf) is fairly
progressive and has the system well to our east by Tuesday night
while the GFS depicts a deeper system that impacts US through
Wednesday. If the GFS verifies, we will likely see some snow above
the 3,500 elevation mark on Tuesday and Tuesday night.

&&

Aviation...as of 4:37 PM PDT Wednesday...VFR conditions this
afternoon are expected to continue into the evening hours...and
for most locations overnight. The marine layer is compressed to
1200 feet. Stratus development will likely stay confined to the
coastal waters and the immediate coastline.

The onshore gradient from sfo-SAC is presently 2.1 mb and not
expected to climb too much higher this evening. However the sfo-SAC
gradient is expected to reach 5 mb Thursday afternoon and evening.
Stronger northwest to west winds will have better chances of bringing ocean
based stratus inland tomorrow evening and night.

Vicinity of ksfo...west wind gusts to 20-25 knots forecast until
05z. VFR tempo MVFR 12z-16z. Moderate to high confidence.

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...VFR is expected this evening. IFR is
forecast to develop between 08z-12z. VFR is forecast to return by
17z Thursday.

&&

Marine...as of 11:00 am PDT Wednesday...a strong north to south
surface pressure gradient is resulting in moderate to strong winds
along the coast this morning. Gale force winds are expected along
the northern outer coastal waters through this evening. Locally
strong winds are possible downwind of coastal points such as pt
sur. Moderate to strong winds are anticipated to persist into the
weekend. The prolonged period of steady wind will result in large
steep seas even outside of the areas of strongest winds.

&&

Mtr watches/warnings/advisories...
... Pt to pt pinos 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm from 9 PM
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm from 9 PM
glw...pt Arena to pt Reyes 10-60 nm until 9 PM
glw...pt Reyes to Pigeon pt 10-60 nm until 9 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm from 8 PM
glw...Pigeon pt to pt pinos 10-60 nm until 8 PM
Small Craft Advisory...Monterey Bay until 9 PM

&&

$$

Public forecast: Bell
aviation: canepa
marine: Larry

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