Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 271750
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
Issued by National Weather Service Los Angeles/Oxnard Ca
1050 AM PDT Thu Apr 27 2017

...new aviation discussion...

.SYNOPSIS...A mostly sunny but breezy but still seasonably cool
day is expected today. Continued breezy at times Friday, near the
coast and in the hills with a gradual warming trend. Winds will
ease by Saturday morning then clear and warm weather is forecast
over the weekend and into early next with no rain in the extended
forecast.

&&

.DISCUSSION...as of 9:00 AM PDT Thursday...The previous discussion
below remains on track as an upper level ridge begins to build
over the western Pacific leaving central California in northwest
flow aloft. Low level stratus and fog is gradually mixing out this
morning and should dissipate completely in the next hour or so.
Surface high pressure will strengthen under the building ridge
allowing for northerly winds to increase through the day today.
Wouldn`t be surprised to see some gusts to 35 mph on the North and
East Bay hills Friday morning as an offshore tight pressure
gradient develops. See the previous discussion below for more
details.

&&

.PREV DISCUSSION...as of 3:39 AM PDT Thursday...Still getting a
few tips of the rain bucket in the Santa Cruz mountains and hills
of Monterey county with northwest post frontal onshore flow in
place. Low cloud product shows the North Bay is nearly clear of
clouds now which is supported by a 5 mb Arcata to SFO gradient,
which is the usual rule of thumb for scouring clouds out of the
North Bay. Areas of clouds south of the Golden Gate should clear
by late morning with any morning coastal drizzle ending around 15z
or so.

Synoptic pattern today features cyclonic flow aloft with strong
onshore surface pressure gradients that will kick up strong
afternoon northwest winds along the coast and coastal hills,
keeping a chill in the air this afternoon.

Overnight as the main longwave trough digs over the Great Basin
the response along the California coast will be a developing
thermal trough at the surface which will push the winds to a more
north or northeast direction by Friday morning. This will bring
some 35 mph winds to the North and East Bay hills Friday morning
and allow for some favorable downslope winds. So under clear
skies expect temperatures to warm well into the 70s to wind out
the work week.

Winds will ease for a time Friday afternoon, except right at the
beaches where north winds will continue. Then again Friday night
into Saturday another round of offshore winds will develop in the
hills. This time with a drier and warmer airmass in place. This
will set the stage for a magnificent Saturday morning to start out
the Bay Area weekend. If you get out early enough you`ll almost
be able to smell the warmth as the offshore winds usher in a drier
airmass with no marine layer to speak of. Saturday should be the
warmest day so far this year for many locations with highs
climbing into the 80s for may of the inland valleys, especially in
the North and East bay where favorable downslope wind flow will
continue.

By Sunday the offshore winds will have eased but the stage will be
set for several days of ideal spring time weather with clear skies
and daytime highs generally in the 70s and 80s for much of the Bay
Area and likely even some near 90 degree readings for southern
Monterey county.

The earliest it looks like the ridge will break down would be
around next Thursday. Will see if we get any stratus intrusions
before that but it looks like a real nice period of warm and dry
weather coming up for the region.

&&

.AVIATION...as of 10:45 AM PDT Thursday...For 18z tafs. Currently
VFR across all sites. Increasing NW winds are expected by this
afternoon with gusts approaching 30 kt possible at SFO by 22z.


Vicinity of KSFO...Expecting conditions to remain VFR through the
period. W-NW winds are expected to increase by this afternoon with
gusts up to 30 kt possible. Winds should begin to decrease late
tonight.


SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Currently VFR at MRY and SNS. VFR
conditions are expected to prevail through the period.


&&

.MARINE...as of 09:00 AM PDT Thursday...The forecast remains on
track this morning with high pressure taking over the weather
pattern. The pressure gradient will tighten across the waters in
response to building high pressure causing northerly winds to
increase over the next couple of days. Wind gusts as high as 25 to
30 kt will become more frequent today and Friday. Some isolated
gale force gusts will even be possible offshore and near coastal
points. Then fresh north winds will persist into the weekend. Seas
will become quite steep due to the winds and a mid period
westerly swell will continue to impact the waters through the
weekend. The existing small craft advisories will remain in
effect.


&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 9 PM PDT Friday for PZZ540-545-560-
     565-570-575.

     Small Craft Advisory until 3 AM PDT Friday for PZZ535.

&&

$$

SHORT TERM...99
LONG TERM....99


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