Small Craft Advisory 198, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
549 PM PDT FRI SEP 9 2016

.SYNOPSIS...Look for continued period of overnight clouds and
patchy fog with mostly sunny conditions during the day. An upper
level low dropping in the Great Basin will bring cooler weather to
the area early next week.

&&

.DISCUSSION...as of 3:00 PM PDT Friday...Mostly sunny conditions
across our region today as clouds burn-off to coastal area late
this morning. Temperatures have been running close to yesterday's
numbers. So far, inland areas have mostly been in the 70s and 80s
with generally 60s at the coast. Tonight should be a near repeat
of yesterday with another round of clouds and patchy fog forecast.

The main concern for the shift was the possibility for convection
on Saturday through Saturday night as a weak area of instability
moves toward our CWA from the south. Models have increased
convective parameters (modified total totals now over 30) and RH
values off of time-height plots have been bumped up above 70% at
times. MUCAPE values remain very low -- generally under 100 J/KG
however with everything pointing to an outside chance for
showers/t-storms they were added to the grids through late
Saturday night. Any chance should be south of the Bay Area.

Cooler air will return next week as energy from the north breaks
off and forms into an upper level low near our CWA. Although
precipitation is not expected, breezy conditions may occur
depending on the eventual track of the low. Models are keeping the
bulk of the moderate wind well above the surface, however with
some CAA expected (nearly 10C from late Sunday to Tuesday) the
models may be underdoing speeds near the surface. This will also
feature the first time in a long time that higher elevation spots
cool off into the 40s and 50s.

&&

.AVIATION...as of 5:48 PM PDT Friday...VFR inland, IFR cigs along
the immediate coast presently, and SFO-SAC continues onshore at 3
mb. Onshore winds usher stratus and fog inland tonight and Saturday
morning. Broad mid-upper level ridge from the eastern Pacific to
the Desert Southwest is providing stable weather conditions over
the forecast area with the marine layer 1,300-1,600 feet deep.

Vicinity of KSFO...VFR this evening, MVFR transitioning to IFR
late tonight and Saturday morning.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...IFR cigs developing this evening, IFR
prevailing tonight and Saturday morning. VFR likely late Saturday
morning and afternoon.

&&

.FIRE WEATHER...As of 4:00 PM PDT Friday...Little change is
expected going into Saturday. Warm and dry conditions will
continue inland and in the hills above the marine layer. The
marine layer depth is forecast to continue near 1500 feet through
Saturday. Winds in the vicinity of the Soberanes Fire will remain
light, mainly from the north tonight, switching to westerly by
Saturday afternoon. A weak upper low off the coast of southern
California will drift slowly northward over the next 36-48 hours.
Mid level moisture is expected to increase as the low approaches
and so there is a slight chance of thunderstorms over Monterey
County from late Saturday afternoon through Sunday morning. If
thunderstorms do develop, they could produce dry lightning.

A cooling trend is forecast from Sunday through Tuesday.

&&

.MARINE...as of 02:40 PM PDT Friday...Light southwesterly winds
will continue through most of the weekend. after that winds will
then begin strengthening out of the northwest...with strongest
winds over the northern outer waters. on the seas...a dominant
short period northwest swell and a longer period southwest swell
through the weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...None.

PUBLIC FORECAST: Bell
AVIATION: Canepa
MARINE: DRP
FIRE WEATHER: Dykema

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