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Area forecast discussion 
National Weather Service San Francisco Bay area
217 PM PDT Fri Oct 21 2016

Synopsis...temperatures will cool off to closer to normal by
this weekend as high pressure currently over the West Coast moves
to the east. An unsettled weather pattern is expected to develop
early next week with rain chances on Monday and Tuesday and then
again late in the week.

&& of 3:00 PM PDT Friday...mostly sunny conditions
across our County Warning Area today although over the past few hours clouds have
been advancing back to the immediate coastline. Temperatures have
generally been running just under values from Thursday except
around Monterey Bay where a more pronounced sea breeze has values
up to 20 degrees cooler than yesterday.

Additional cooling can be expected over the weekend as 500 mb
heights continue to lower as the ridge axis shifts farther to the
east. A longwave trough will head toward the West Coast with the
potential for some light drizzle ahead of it to get into the
North Bay Sunday afternoon or evening. For other spots the only
impact will be to keep highs in the 60s to mid 70s.

By Monday an upper level low will advance to just west of the
British Columbia/Washington coastline while an associated frontal system moves down the
coast. Rain will likely get into the San Francisco Bay region
Monday night and possibly into portions of Monterey Bay going into
Tuesday. Precipitable water values are forecast to be 1 to 1.15" which is
considerably less than the values from the past couple of systems.
Rainfall amounts will range from locally more than 1" over the
North Bay to 1/10" to 1/3" around sf Bay. Locations south of Santa
Cruz will probably see little to no rainfall. Highs will be in the
60s to lower 70s.

After a break in the rain, models have been showing the potential
for another system to bring rainfall back to our region.
Disagreement between the various solutions as far as timing and
location of the main moisture plume (pw values over 1.30") makes
it difficult to provide much specificity for Thursday into
Saturday. For now will go with chance pops for the entire period
until better agreement is reached. CPC does continue to highlight
above normal rainfall for Thursday of next week through most of
the following week with the highest likelihood for Monterey
County southward.

&& of 11:00 am PDT Friday...for 18z tafs...widespread
VFR today ahead of an approaching trough. High clouds will spread
southward through the day at or above 20000 ft. Winds will be
breezy along the coast in the afternoon but gradually weaken
overnight. A compressed marine further south ahead of the front
will bring patchy fog posbl to kmry ksns kwvi. Further north,
instead expect to see brief intrusion into the Bay area around
sunrise around 600-900 feet around sunrise as marine layer Springs

Vicinity of ksfo...VFR. Light winds increasing this afternoon to
around 20 kt. Chance to see some brief IFR cigs around sunrise

Sfo bridge approach...similar to ksfo.

Monterey Bay terminals...VFR today with light winds. Chance to see
vlifr due to patchy fog around sunrise tomorrow.

&& of 10:55 am PDT Friday...moderate northwest winds
will continue today ahead of an approaching trough. The strongest
winds will be around Point Reyes and Point Sur. Winds will
gradually ease through the weekend as low pressure descends into
the region. This low pressure will bring a longer period
northwest swell to the area.


Mtr watches/warnings/advisories...
... Pt to pt pinos 0-10 nm
Small Craft pinos to pt Piedras Blancas 0-10 nm
Small Craft Arena to pt Reyes 0-10 nm
Small Craft Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm until 9 PM
Small Craft Reyes to Pigeon pt 0-10 nm until 3 am



Public forecast: Bell
aviation: drp
marine: drp

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