Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1056 am PDT Thursday Oct 8 2015
Synopsis...dry weather conditions along with a warming trend
will persist through late in the week as high pressure builds over
the state. Temperatures will hold steady through the weekend as
the ridge flattens and zonal flow develops aloft.
Discussion...as of 9:45 PM PDT Thursday... a positively tilted
eastern Pacific Ridge is strengthening over California this
morning. This 596dm ridge is anchored near 30n 130w... which is
around 500 miles offshore to the west of San Diego. Temperatures
are expected to be mildly warmer today compared to yesterday...
with little to no change expected on Saturday.
Satellite imagery shows partly to mostly cloudy conditions over
the state despite the building high pressure aloft. These middle to
high level clouds are the result of moisture wrapping over and
around the ridge of high pressure. This and additional moisture
is being advected northeastward from the tropics by a potent upper
low in the Gulf of Alaska. This upper low is forecast to shift
inland well to our north through the weekend. The bulk of the
precipitation will fall well to our north in the Pacific
northwest and northern coastal California. Short to medium term
guidance looks bearish for precipitation over most of the forecast
area... however some uncertainty exists over the probability of
precipitation over Sonoma and Napa County so can not entirely rule
out a few drops of rain there through the weekend. Temperatures
will hold steady...and remain warm...through the weekend as the
ridge gives some sway to the upper low to the north.
By early next week... the ridge reasserts dominance over the
state... resulting in additional warming on Monday and Tuesday. By
midweek a weak shortwave trough will flatten the ridge slightly...
leading to slightly cooler temperatures. Temperatures are expected
to remain a few to several degrees above normal through all of the
ups and Downs of the upcoming week. Meanwhile... the upper low
that moved through the area last weekend will retrograde upstream
and undercut next weeks ridge. Late next week... this upper low could
once again influence our weather... almost two weeks after it
first brought windy conditions to our area last weekend.
Aviation...as of 11:00 am PDT Thursday...ridge of high pressure
overhead along with offshore flow at the surface should keep VFR
conditions through the period. Only possible fog formation is
around koak with even that looking unlikely.
Vicinity of ksfo...VFR conditions expected through the period.
Winds of 280 to 300 expected to increase through the day with
gusts to 20 knots possible through at least 05z. High confidence.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR conditions and winds under 12kt expected
through the period. High confidence.
Marine...as of 09:06 am PDT Thursday...look for increasing
northerly winds especially over the southern waters by this
afternoon. Gentle seas will persist into the weekend with a mixed
swell. A moderate period west to southwesterly swell generated by
hurricane oho will enter the waters beginning roughly Friday
lasting into the weekend.
... Pt to pt pinos 0-10 nm from 2 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 2 PM
Public forecast: drp
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