Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
834 PM PDT sun may 3 2015
Synopsis...a deep marine layer will maintain low clouds and fog
along the coast and inland valleys through midweek. A trough of
low pressure will pass over the area midweek mixing out the marine
layer and promoting a slight chance of showers around the
area...especially over the mountains. Otherwise expect slightly
below normal temperatures continuing through the week.
Discussion...as of 8:34 PM PDT Sunday...low clouds are returning
to the area this evening. The Fort Ord profiler is indicating that
the marine layer has deepened to nearly 3000 feet. The final low
light visible satellite image was showing low clouds in place along
the coast and also impacting Marin and Sonoma County. A step
outside revealed low clouds moving into the Monterey area. With
the deep marine layer in place with onshore flow most location's
afternoon temperatures were at least slightly below normal with
some locations such as Sonoma County Airport 10 degrees below
The current satellite water vapour image is showing a low pressure
system centered at 49 north 142 west with a broad area of low
pressure positioned offshore of Southern California. The 1200z
European model (ecmwf) and 1800z gfs40 have initialized well with these synoptic
features and remain in good agreement through the forecast period.
Both models move the North Pacific low into the Pacific northwest
and northern California by middle week. This low will mix out the
marine layer providing some relief from the low clouds and fog to
the area. This low will also promote a slight risk of precipitation
across the area on Thursday and Friday. Otherwise expect slightly
cooler than normal temperatures to persist through the upcoming
week. The current forecast package covers the expected weather
well so no updates are needed at this time.
Aviation...as of 4:45 PM PDT Sunday...southwest flow at the coast
will allow stratus to spread into the North Bay valley and the mry
Bay area early tonight. Clouds will spread through the Golden Gate
into the sfo Bay area but sfo and Oak should stay VFR until after
Vicinity of ksfo...southwest flow will keep MVFR ceilings out until
after 06z. Southwest winds to 15 knots through 04z.
Sfo bridge approach...similar to sfo.
Monterey Bay area terminals...MVFR ceilings after 03z.
Beaches...as of 4:36 am PDT Sunday...beach hazard statement
continues through tonight for strong rip currents and large shore
break. Buoys off the northern and central California coast show
mixed swells of 3 to 5 feet with 24 second period and 5 to 7 feet
at 11 seconds. The long period waves will result in exceptionally
strong rip currents along the coast especially on southerly facing
beaches such as Stinson Beach in Marin County and the beaches
along the Monterey Bay coast of Santa Cruz County.
Additionally...these long period waves will also result in large
shore break at Twin Lakes state beach and the Santa Cruz boardwalk
beach. Large shore break can result in neck and back injuries. If
you plan on entering the water please do so near a lifeguard and
always keep an eye on the ocean when visiting the beach.
Marine...as of 10:31 am PDT Sunday...gusty northerly winds will
continue over the northern outer waters through early next week.
Elsewhere...southerly flow will continue today. Northerly flow
will develop over most of the coastal waters tonight and Monday as
high pressure builds over the region. A long period southerly
swell will impact the coastal waters today and continue through
... Arena to pt Reyes 10-60 nm
Small Craft Advisory...sf Bay north of the Bay Bridge until 9 PM
Public forecast: Larry
aviation: west pi
marine: west pi/Sims
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