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Area forecast discussion 
National Weather Service San Francisco Bay area
618 PM PDT Wednesday Apr 1 2015

Synopsis...a weak Pacific storm system moving inland to our north
will maintain cool...dry and breezy conditions through Thursday. A
slight warming trend is then expected for late week as a brief ridge
develops over the region. A stronger system will then approach the
northern California coast and bring chances for precipitation back
to the region from Sunday into early next week.

&& of 01:59 PM PDT Wednesday...a middle/upper level
trough continues to push into the Pacific northwest this afternoon
with high level clouds ahead of the system streaming across the
region. Temperatures are also cooler at this hour compared to 24
hours ago as a result of the colder air mass associated with this
system. Meanwhile...dry weather conditions continue region-wide
with any precipitation remaining well to our north. While a much
colder air mass is expected to advect into the region
overnight...increased wind speeds should help prevent frost
development over most interior locations of the North Bay.
However...can not rule out patchy frost in a few of the most
sheltered locations early Thursday and Friday mornings when
temperatures bottom out in the middle 30s. Daytime temperatures will
slowly rebound Thursday through Saturday as the aforementioned
trough shifts inland and a weak ridge builds over the state.

A deeper middle/upper level system is forecast to drop southward out of
the Gulf of Alaska late in the week into the upcoming weekend.
Moisture advection will increase across our region ahead of this
system Saturday night into Sunday and with the approach of a
frontal boundary...chances for precipitation will increase over the
northern half of the region by Sunday morning. Lingering showers
will be possible through Monday afternoon with a cooler...more
unstable airmass aloft. At this time...rainfall amounts are forecast
to remain low (generally less than 1/10 of an inch).

With the main upper level feature remaining off of the Pacific
northwest coast early next week...rain chances will continue over
portions of the region into Tuesday. The latest models show the
trough slowly pushing inland on Monday with precipitation
progressing southward down into the Monterey Bay region Monday night
into Tuesday morning. This is when the best chances for widespread
rainfall are expected. The wpc 7 day quantitative precipitation forecast predictions continue to
show 1/4 to 1/2 inch rainfall amounts over much of the region with
higher totals across the North Bay hills/mountains. Along with the
rain chances...cooler temperatures are also expected Sunday into
early next week as these systems impact the region. The medium range
models then show a brief drying trend for the middle of next week
followed by another middle/upper level system that could potentially
bring additional precipitation to portions of the San
Francisco/Monterey Bay region late next week.

&& of 6:10 PM PDT Wednesday...a cold and dry upper
level trough will move east over the Bay area early this evening
then reach the Great Basin after midnight. Late afternoon diurnal
warming resulted in a few areas of minor instability clouds over
northern Napa...San Mateo...Santa Cruz and northern Monterey
counties. These clouds could linger for a few hours after sunset
as air mass cooling...northwest winds and terrain forcing hold them
together a bit longer but they should mostly dissipate by midnight
as the winds gradually subside. Non-convective low level wind
shear (llws) is not likely at this time but will monitor winds as
some areas are likely to see surface Delaware-coupling overnight. Gusty
winds may linger the longest over the northern half of the forecast
area this evening due to a well mixed air mass and upper level jet
stream convergence and subsidence. Moderate to high confidence VFR
for the period.

Vicinity of ksfo...peak westerly wind gusts to 33 knots so far and
1 min observation showing upper 20s at the moment. Winds holding greater
than 20 knots until 04z. VFR.

Sfo bridge approach...similar to ksfo.

Monterey Bay area terminals...gusty westerly winds should subside
and eventually Delaware-couple by 08z-09z kmry and ksns. VFR.

&& of 10:23 am PDT Wednesday...another windy day over
the coastal waters as high pressure continues to produce gusty
northerly winds. Local gale force gusts will be possible. Building
northwest swell in conjunction with building fresh swell and mixed
seas will lead to hazardous maritime conditions along the central


Mtr watches/warnings/advisories...
... Pt to pt pinos 0-10 nm until 5 am
Small Craft pinos to pt Piedras Blancas 0-10 nm until 5 am
Small Craft Arena to pt Reyes 10-60 nm
Small Craft Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft pinos to pt Piedras Blancas 10-60 nm
Small Craft Arena to pt Reyes 0-10 nm
Small Craft Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...rough bar advisory for sf bar until 3 am
Small Craft Advisory...Monterey Bay until 11 PM



Public forecast: rgass
aviation: canepa
marine: mm

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