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Area forecast discussion 
National Weather Service San Francisco Bay area
1113 PM PDT Monday Aug 29 2016

Synopsis...an upper level system and associated cold front will
push through the region overnight tonight into early Tuesday morning
and result in breezy winds, slightly cooler temperatures and the
slight possibility of dry thunderstorms over the North Bay. A broad
troughing pattern over the West Coast will result dry weather
conditions along with temperatures below seasonal averages through
the remainder of the week.

&&

Discussion...as of 9:00 PM PDT Monday...an upper level low
spinning approximately 450 nm west of San Francisco will approach
the state tonight. The low and the associated cold front will
bring increasing mid/upper level clouds across the region tonight
into Tuesday morning. A slight chance of elevated convection will
persist over the North Bay however models indicate the moisture
associated with this system is moving in over the region between
500-300 mb which is slightly higher than ideal 700-500 mb level
for elevated convection over our area. Models also have pushed the
treat further north then previous runs. While the chance for
elevated convection and dry lightning over our area appear to be
dwindling the forecast will maintain a slight chance across the
North Bay through tonight. Winds will be another factor to contend
with tonight into Tuesday morning. Strong and gusty west to
northwest winds of 30 to 40 mph are expected behind the front
however the latest ob from Altamont RAWS reported gusts to 39
mph. Therefore anticipated gusty conditions through the rest of
tonight and into Tuesday.

From previous discussion...in wake of the frontal passage, the
airmass will become more stable by Tuesday afternoon with the
threat for convection diminishing and wind speeds relaxing late in
the day. Temperatures will generally be a few to several degrees
cooler compared this afternoon as well. Do expect some disruptions
to the depth of the marine layer, however should see enough
boundary layer moisture to allow for low clouds to return to the
coast tonight and spread locally inland through Tuesday morning.

A longwave trough is then forecast to remain stretched along much of
the West Coast through late week. This will keep temperatures below
seasonal averages, especially inland, with rounds of
overnight/morning low clouds that will give way to mostly sunny
conditions each afternoon. In addition, should see continued dry
weather conditions outside of the potential for coastal drizzle late
in the week.

&&

Aviation...as of 11:12 PM PDT Monday...VFR this evening as mixing
out ahead of an eastern Pacific trough and lower to mid level cold
air advection steadily bumps up against a strong sub-tropical ridge
over California. Low confidence cloud cover forecast tonight and Tuesday
morning. Kmux is picking up on a few very high based echoes, near
20 thousand feet, about 40-70 miles SW-west of Sonoma County, precip
likely evaporating aloft.

Vicinity of ksfo...westerly winds with gusts to the 20 knot range
this evening, VFR persists. Low confidence MVFR cig forecast 12z-16z
Tuesday. VFR forecast Tuesday late morning and afternoon.

Sfo bridge approach...similar to ksfo.

Monterey Bay terminals...VFR persists this evening, low confidence
MVFR late tonight and Tuesday morning. VFR returning late Tuesday
morning, clearing could be quick process and thus possibly earlier
than usual.

&&

Marine...as of 9:20 PM PDT Monday...high pressure off the coast
of central California will cause a tightening of the pressure
gradient over the coastal waters this afternoon through midweek.
As a result...northerly winds and steep short period waves will
build on top of a small southerly swell. Expect near gale to gale
conditions in the Lee of Prominent Point such as Point Sur.
Conditions are forecast to remain strong into the weekend...though
an approaching upper trough may disrupt this pattern.

&&

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 Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
glw...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...sf Bay until 3 am

&&

$$

Public forecast: CW
aviation: canepa
marine: bfg



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