Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
502 am PDT Monday Aug 29 2016
Synopsis... fair weather conditions will persist through our
region today slightly below seasonal temperatures forecast. A low
pressure disturbance will impact the area tonight into tomorrow,
bringing breezy winds, slightly cooler temperatures and a minor
possibility of dry thunderstorms over the North Bay. A mean trough
pattern will bring continued below seasonal temperatures through
the end of the week.
Discussion...as of 3:00 am PDT Monday...unlike countless previous
morning, the satellite is finally showing breaks in the stratus
both along the coast along with adjacent inland locations. Fort
Ord profiler also indicates that the depth of the layer has
dropped to less than 1,500 feet marking the lowest value in quite
some time. In addition, the northerly gradient jumped to over 2 mb
Sunday evening (although now at 1.4 mb). With more patchy cloud
cover, should see a larger portion of our County Warning Area with clear
conditions. Despite that, highs will generally remain below
normal with inland highs mostly in the upper 70s to near 90.
Coastal spots will be in the 60s to lower 70s.
Main focus for the shift has been on an area of moisture
associated with Tropical Storm Madeline that will move to the
northeast toward the northern part of our County Warning Area this evening into
Tuesday. Model guidance off the NAM indicates modified total
totals potentially hitting 31-32 for a brief period along with positive vorticity advection which
would favor the possibility of elevated convection. However,
other models keep the convection and positive vorticity advection out of our County Warning Area.
Ensembles indicate only a 5-10% chance of anything firing up, so
will keep very low pops going with a mention of thunderstorms. As
the previous shift mentioned, due to poor performance from a setup
in 2008 that lead to a massive lightning outbreak, we are using
extra caution. Biggest concern remains for Marin and Sonoma
counties. More stable air returns by Tuesday evening.
A longwave trough will position itself along the West Coast for
Wednesday through at least the weekend. The trough will also lead
to a deeper marine layer with onshore flow forecast at the
surface. This will keep temperatures near to below normal for at
least the next 10 days.
Aviation...as of 4:50 am PDT Monday...stratus was slow to spread
into the sfo and mry Bay area but now extends well inland. Bases
are high and the marine layer has compressed from yesterday.
Therefore an earlier burnoff time is expected. Onshore winds will
increase this afternoon as high pressure builds off the central
Vicinity of ksfo...MVFR through 17z. West to northwest winds
increasing to 20-22 kt with gusts to 30 kt after 20z.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...cigs are lower in the mry Bay area and
may be slower to clear than the sfo Bay area. IFR through 17-18z.
Locally gusty west-northwest winds after 20z.
Marine...as of 4:50 am PDT Monday...high pressure will
strengthen off the central and Southern California coast Monday
resulting in increasing northwesterly winds. These winds are
forecast to persist through the week.
... Arena to pt Reyes 0-10 nm from 3 PM
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 3 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm from 3 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 3 PM
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm from 3 PM
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm from 3 PM
Small Craft Advisory...mry Bay from 3 PM
Small Craft Advisory...sf Bay from 3 PM
Public forecast: Bell
aviation: west pi
marine: west pi
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