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Area forecast discussion 
National Weather Service San Francisco Bay area
135 PM PST Monday Dec 22 2014

Synopsis...aside from early morning coastal and valley fog...dry
weather conditions and mild temperatures will persist through
midweek as high pressure remains over the region. A weak storm
system will then move through northern California and bring a
chance of light rain and cooler temperatures back to the region
late Wednesday into Thursday.

&& of 01:34 PM PST Monday...high pressure will
continue to dominate our weather pattern through midweek with
above average daytime and overnight temperatures. Given the
recent rains across much of the well as abundant low
level moisture...early morning fog will once again be likely near
the coast and across valley locations the next few mornings. The
warmest of the days will likely be Tuesday afternoon...with
temperatures 5 to 15 degrees above seasonal averages.

The ridge is then forecast to weaken by midweek as a middle/upper
level trough digs southeast toward the Pacific northwest. This
system will drop into northern California and across Nevada late
Wednesday into Christmas day. As a result...light rain will be
possible over a portion of the region late Wednesday and
Thursday. However...the fast moving system will keep rainfall
amounts at a minimum south of the San Francisco Bay area.
Meanwhile...the North Bay may pick up a few tenths of an inch
from this passing system. Offshore winds are also forecast to
increase in wake of the frontal passage with breezy and gusty
conditions possible in the higher elevations. Will have to
continue to monitor wind speeds for Thursday and
Friday...especially given the saturated soils and possibility of
downed trees.

In addition...cooler temperatures will return Thursday to the
region in wake of the frontal passage. By Thursday
night...temperatures will likely dip into the 30s and 40s with
the coolest locations being over the North Bay valleys. Near
normal temperatures will then persist through late week and into
the upcoming weekend as the middle/upper level ridge remains off the
West Coast and another reinforcing shot of cooler air slides down
the western portion of the country. Will keep the forecast dry at
this time for late in the forecast period as the secondary system
that drops across the region appears to be lacking sufficient

&& of 10:10 am PST Monday...main concern continues to
be low ceilings and visible across our area with satellite and surface observation
showing a mix of LIFR/vlifr up to VFR. Would expect things to
continue to improve the rest of the morning with MVFR to VFR across
the board by afternoon. Return of at least LIFR tonight into
tomorrow for most terminals due to a very moist boundary layer and
lack of wind. Winds will remains fairly light and not be a factor.
Moderate confidence.

Vicinity of ksfo...LIFR to vlifr currently at sfo which should
continue at least through 19z and possibly to 20z. Conditions
forecast to improve to VFR for the afternoon through around 10z
tonight. IFR forecast to return late tonight into
Tuesday...possibly down to LIFR levels again. Moderate confidence.

Ksfo bridge approach...possible that the southern part of the
approach will scatter out a bit faster today than sfo otherwise
similar to sfo.

Monterey Bay area terminals...VFR at ksns through the day. At kmry
MVFR forecast for the rest of the morning with VFR expected at
kmry around 21z. Moderate confidence.

&& of 9:05 am PST Monday...a building ridge of high
pressure along the coast will keep moderate northwesterly winds
going across most of our waters into Tuesday. Winds will decrease
by Tuesday night as the high moves into the Great Basin. Another
round of moderate northwesterly winds are expected on Thursday as
another high strengthens over the eastern Pacific.


Mtr watches/warnings/advisories...
... Flood Advisory...coastal and Bay Shore areas
Small Craft Arena to pt Reyes 0-10 nm until 3 am
Small Craft Reyes to Pigeon pt 0-10 nm until 3 am
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm until 3 am
Small Craft pinos to pt Piedras Blancas 0-10 nm until 3 am
Small Craft pinos to pt Piedras Blancas 10-60 nm until 3 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



Public forecast: rgass
aviation/marine: Bell

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