Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
842 am PDT Wednesday Aug 20 2014
Synopsis...low clouds today and tomorrow will give way to mostly
sunny conditions inland with partly cloudy skies likely near the
coast. Only slow warming is expected away from the coast Thursday
Discussion...as of 8:45 am PDT Wednesday...typical August weather
pattern with a deep marine layer and widespread clouds along the
coast and valleys. Only difference noted from yesterday is less
drizzle although still getting a few reports of pockets of it.
Should turn mostly sunny away from the coast today with clouds
likely near the Pacific due to a persistent westerly surface
gradient. Highs will be in the 60s to middle 70s at the coast with
middle 70s to around 90 inland -- in other words within a few
degrees of highs from Tuesday.
NAM continues to show an area of instability for eastern Monterey
and southern San Benito counties due to moisture wrapping around
an upper level low, although initialization does not seem to be
handled well, so will continue to discount that solution.
No major update expected for the forecast package.
Previous discussion...an upper level low will remain nearly
stationary over Southern California today before getting kicked
eastward by a deepening upper trough over the Pacific northwest on
Thursday. Marine layer remains deep at around 3000 feet and
stratus extends well inland again this morning. So far the only
reports of drizzle has been in the Watsonville-Corralitos area but
local drizzle with measurements up to a few hundredths of an inch
is possible anywhere along the coast through the early morning
hours. Today will be another cool day. The marine layer should mix
out by afternoon and it will be mostly sunny to partly cloudy. The
marine layer will reform tonight at a lower level so there will
not be as much inland penetration. As a result inland temperatures
will warm up Thursday and Friday but the upper trough over the
Pacific northwest/Great Basin will limit the warmup to about 3-5
degrees at most.
The upper trough will slowly move east Saturday and Sunday but
models indicate a secondary trough moving into the Pacific
northwest. As a result of all this temperatures are not expected
to change much Saturday and Sunday.
Medium range models bring a strong upper ridge in the eastern
Pacific closer to the California coast around Tuesday and
Wednesday of next week. If this verifies there could be more
significant warming over the entire district.
Aviation...as of 5:15 am PDT Wednesday...similar to yesterday
with widespread low clouds across all area terminals. Low clouds
expected to scatter out after 18z this morning. Low confidence.
Ceilings are anticipated to make an early return this evening. Light
onshore flow will strengthen this afternoon.
Vicinity of ksfo...stratus is expected to clear around 18z-19z
this morning. Winds will remain light out of the southwest through
the morning hours then strengthen with the onset of the afternoon
Ksfo bridge approach...low clouds will scatter out over the
approach around 19z this morning...otherwise similar to ksfo.
Monterey Bay area terminals...MVFR ceilings are expected to mix out
late this morning. Light winds will increase to around 10 knots this
Marine...as of 04:53 am PDT Wednesday...moderate northwesterly
winds expected across the northern outer waters this evening and
tonight and over portions of San Francisco Bay during the
afternoon hours. Otherwise generally light winds and seas will
continue. A moderate period south swell will move into the region
later this week due to storms in the tropical Pacific.
... Bay north of the Bay Bridge from noon
Public forecast: Bell/west pi
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