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Area forecast discussion 
National Weather Service San Francisco Bay area
150 PM PDT Wednesday may 6 2015

Synopsis...an approaching upper level system will result in a
chance for showers and thunderstorms over the southern half of the
region Thursday and Friday. Dry weather conditions and slightly
warmer temperatures return for the weekend as the system shifts
inland and high pressure builds over the region.

&&

Discussion...as of 01:48 PM PDT Wednesday...a middle/upper level
low currently over the Pacific northwest is forecast to drop
southward into northern California over the next 12 to 24 hours.
The upper level low is expected to generate showers over the
southern and eastern portions of the region on Thursday morning
as it approaches from the north. Temperatures will also cool
region-wide with a much cooler air mass associated with this
system advects over the region. With the center of the low
forecast to be over the San Francisco/Monterey Bay region Thursday
afternoon...increased instability and heating will lead to
thunderstorm development. At this time...it appears the best
chances for thunderstorms will be over the hills/mountains south
of the San Francisco Bay. This activity will likely persist into
the early evening before diminishing with the loss of daytime
heating by Thursday night.

While the the upper level system will then begin to slowly shift
eastward on Friday...lingering moisture and insatiability will
result in a slight chance of showers and thunderstorms over
higher elevations of Monterey and San Benito County again Friday
afternoon. However...coverage will be more isolated with the
center of the upper level low to our east. The system will then
eject into The Four Corners region on Saturday with weak high
pressure building in over the West Coast. As a result...dry
weather conditions return to the region with a slight warming
trend expected through the weekend.

The medium range models then show another middle/upper level trough
approaching the West Coast early next week. At this time...will
show a slight cooling trend for the first half of the upcoming
week. However...will keep precipitation out of the forecast until
we get better model consistency with regards to the upper level
pattern.

&&

Aviation...as of 11:15 am PDT Wednesday... trough descending from
pacnw into California this morning is clearing coastal stratus
from north to south. Coastal stratus still evident from Monterey
Bay southward with kmry and ksns likely to remain under MVFR ceilings
into the early afternoon. Gusty onshore flow will increase this
afternoon. Breezy onshore persists into the night.

Vicinity of ksfo...VFR conditions with mostly clear skies for
today. Onshore flow increases in the afternoon with sustained
speeds 15 to 25 knots and gusts up to 30 knots possible. MVFR ceilings
return 08-10z tonight.

Ksfo bridge approach...VFR with mostly clear skies. Some haze near
surface.

Monterey Bay area terminals...MVFR ceilings through 20-22z. VFR with
few/scattered clouds 2-3k feet above ground level through the afternoon. Gusty sea
breeze push again this afternoon with gusts up to 25 knots posbl.
MVFR ceilings return 02-04z.

&&

Marine...as of 9:15 am PDT Wednesday...moderate to strong
northerly flow will continue over the coastal waters today. Gale
force winds are expected over the northern waters...including
north of pt Reyes within 10 miles of the coast...and north of
Pigeon Point beyond 10 miles of the coast through late tonight.
The strong winds will produce hazardous conditions with steep wind
waves and fresh swell. Wind and waves will gradually decrease over
the weekend.

&&

Mtr watches/warnings/advisories...
... 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 from 3 am
glw...pt Arena to pt Reyes 0-10 nm until 3 am
glw...pt Arena to pt Reyes 10-60 nm until 3 am
glw...pt Reyes to Pigeon pt 10-60 nm until 3 am
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm from 3 am
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm from 3 am
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...rough bar advisory for sf bar
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Small Craft Advisory...sf Bay south of the Bay Bridge until 9 PM
Small Craft Advisory...Monterey Bay until 9 PM

&&

$$

Public forecast: rgass
aviation/marine: drp

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