Scientific Forecaster Discussion
fxus66 kmtr 241201
Area forecast discussion
National Weather Service San Francisco Bay area
501 am PDT Sat Jun 24 2017
Synopsis...typical Bay area weather pattern returns for the
weekend and into next week. Expect areas of night and morning low
clouds and fog followed by sunny and seasonably warm afternoons.
Discussion...as of 3:46 am PDT Saturday...the marine layer has
deepened to around 1500 feet early this morning with onshore
gradients from sfo to SAC at 3.2 mb. This has set the stage for
efficient transport of cool marine air into the valleys. Out in
the Delta, Travis Air Force Base the wind observation is
sustained at 26 kt with gusts to 33 kt. Latest satellite fog
product and surface observations Show Low clouds now inundating
the entire sf Bay and 880 corridor as well as most of the Sonoma
County valleys. Thus expect continued cooling trend for all inland
areas after this weeks hot conditions.
One item we are watching early this morning is some moisture and
associated convection over the waters west of San Diego. The
models bring this moisture northward into the coastal range of
Santa Barbara and then eventually farther northward towards the
Monterey County line later this morning and afternoon. Some of the
short term models are hinting at possible isolated convection
over the higher terrain of southern Monterey and San Benito
counties. Have tried to fine tune some of these details and left
15% pops near Santa Rita Peak as well as portions of the Los
Padres National Forest. Confidence is low on development but cant
completely rule out with main impacts for fire weather concerns
and mainly campers/outdoor interests in these remote sections of
Otherwise expect continued modest cooling into Sunday as an upper
trough approaches the offshore waters and strengthens the onshore
flow as the marine layer will likely deepen to around 2000 feet.
90s should be confined to only the most interior sections of the
district while more temperate upper 60s to lower 80s will be the
Its not surprising as we enter the last week of June and the
official end of the rain year that the pattern will become benign
with zonal or weak cyclonic flow aloft. A persistent/climo
forecast will probably be the best forecast tool suggesting
seasonable daytime highs/lows as the marine layer extends inland
at night and retreats to the coast by late morning.
Aviation...as of 05:00 am PDT Saturday...for 12z tafs.
Widespread marine stratus intrusion overnight bringing LIFR to
MVFR cigs to most taf sites... with some VFR deeper inland.
Looking for similar clearing out times this morning versus
yesterday morning given similar stratus intrusion and depth though
gradients differ. Otherwise... generally light winds today,
except breezy conditions along the coast by the afternoon through
the evening. Some elevated moisture moving in from the south has
the slight potential of bringing rain showers/thunderstorms. Low
clouds return tonight.
Vicinity of ksfo...IFR to MVFR through around 1630-1730z. Similar
to yesterday. Onshore winds increasing to become breezy in the
afternoon. Low clouds return tonight.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...IFR/LIFR along the Monterey Bay this
morning through the mid to late morning. Brief clearing through
the afternoon with an early return of clouds tonight. Light winds.
Marine...as of 04:58 am PDT Saturday...generally light but
increasing southerly winds today. The strongest winds will be
along the Big Sur and Santa Cruz coastlines. Generally light
northwest seas with decreasing swell heights.
... Pinos to pt Piedras Blancas 0-10 nm from 9 am
Small Craft Advisory...sf Bay from 12 PM
Public forecast: rww
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