Strong Wind in California, May 9, 2017

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1031 PM PDT Mon May 8 2017

.SYNOPSIS...High pressure building over the region will result
in a warming trend into Tuesday. Temperatures trend cooler on
Wednesday as the ridge breaks down and onshore flow increases
ahead of our next approaching system. Much cooler and breezy
conditions return region-wide late in the week with a slight
chance of showers across the North Bay on Thursday. Temperatures
below seasonal averages and mainly dry conditions will then extend
into the upcoming weekend.

&&

.DISCUSSION...as of 8:55 PM PDT Monday...High pressure building
over the Eastern Pacific brought warmer temperatures across much
of the region today with exception to the immediate coast where
strong and gusty onshore flow and areas of low clouds allowed
temperatures to cool slightly. Inland temperatures however saw
anywhere from 5 to 10 degrees of warming with areas such as
Bradley and Fort Hunter Liggett warm 13 and 14 degrees,
respectively, over yesterdays highs to a seasonal high of 83
degrees.

The high over the Pacific is forecast to ridge across the Pacific
Northwest tonight and settle in over the Great Basin while a
thermal trough situates itself along the coast. This will result
in light offshore flow across the hills tonight into Tuesday and
allow for one more day of seasonably warm temperature with highs
in the mid 60s to lower 70s along the coast and 80s inland.

Low clouds will likely remain confined to the immediate coast
overnight and Tuesday with only minimal intrusion over the
Monterey Bay and down the Salinas Valley. Areas north of the
Monterey Bay are expected to only see patchy low clouds along the
coast overnight.

From previous discussion...The warming trend is then forecast to
be shut down by an increase in onshore flow and marine influence
on Wednesday. In addition, a southerly surge continues to look
possible late Tuesday into Wednesday morning with low clouds,
potential fog and coastal drizzle along the Big Sur coast
northward toward the Golden Gate. Daytime temperatures on
Wednesday will cool by a few degrees at the coast to around 10
inland which will greatly be dependent on the timing and
development of the sea-breeze.

By late week, another mid/upper level trough is forecast to drop
southward toward the region and will usher in another around of
cooler temperatures. In addition, cannot rule out a slight chance
of rain showers across the North Bay on Thursday as a weak frontal
boundary drops into the region. However, widespread rainfall is
not likely. The trough is forecast to linger through late week and
into the upcoming weekend with temperatures running below
seasonal averages along with breezy northwesterly winds.

Longer range model guidance suggests cooler than average
temperatures will then persist into much of next week as a
reinforcing shot of cooler air drops down the West Coast.
Additionally, the ECMWF and GFS both indicate the possibility of
unsettled conditions early next week with the chance of light
precipitation. However, the solutions do differ in the details and
timing at this time.

&&

.AVIATION...As of 10:31 PM PDT Monday...The marine layer slopes
from 500-600 feet in the Bay Area to 1200 feet on the north Central
Coast this evening. A strong upper level ridge will continue to
reinforce and compress marine inversions resulting in IFR cigs and
vsbys along the immediate coastline and into the Salinas Valley
tonight, onshore breezes also pushing some stratus and fog through
the Golden Gate later tonight and Tuesday morning.

Current stratus appearance is quite similar looking to a stratus
surge already while the SMX-SFO gradient is 1.2 mb and forecast
to peak to 3-4 mb Tuesday evening; often the NAM is up to 12 hours
(or in isolated instances up to 24 hours) late with predicting
the onset of a southerly surge. At any rate surge development may
couple with Tuesday's daytime heating and seabreeze circulation.
Bottom line, expect gusty winds over the San Francisco Bay waters
Tuesday possibly well into Tuesday night (an update was issued for
marine), and it may become gusty at KOAK and KSFO Tuesday into
Tuesday night as well. 06z tafs will reflect gustier winds. Also,
the 18z and 00z NAM model runs both showed significant lower level
cooling 12C-13C beginning very early Wednesday morning over the
North Bay counties. Most likely this will equate to lots of wind
accompanying stratus over the bay waters over to the Delta with
northward overlap into the North Bay counties.

Vicinity of KSFO...VFR. Westerly winds near 10 knots becoming NE 5-10
knots Tuesday morning then W-NW and possibly strong and gusty Tuesday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Stratus within an eddy circulation over the
bay this evening may be early signature of stratus surge. IFR cigs
prevailing into Tuesday, clearing may be slow Tuesday with plenty
of stratus enveloping the immediate coastline.

&&

.MARINE...as of 9:30 PM PDT Monday...Strong and gusty northwesterly
winds will persist mainly over the outer waters into mid-week. The
gusty winds will result in fresh swell and steeper wind waves which
will then subside later this week. Gusty westerly winds will develop
over the bays Tuesday and Tuesday night.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm

&&

PUBLIC FORECAST: CW
AVIATION/MARINE: Canepa

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, twitter, and youtube at:
www.Facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea