Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
908 am PST Monday Nov 24 2014
Synopsis...high pressure will bring sunny and seasonably warm
weather today through Thanksgiving day with dry weather for the
Bay area and California. The ridge will break down by Friday with
rain chances increasing north of the Golden Gate by Friday
evening. Rain chances will spread southward through the rest of
the Bay area and central coast Saturday into Sunday.
Discussion...as of 08:53 am PST Monday...high pressure building
over the region has resulted in a cool start to the day with
temperatures generally in the 40s...in the lower 30s in many
inland sheltered locations. Temperatures by this afternoon will
warm into the upper 60s to lower 70s inland as the air mass aloft
continues to warm through midweek. The ongoing forecast remains on
track with no updates needed at this time.
Previous discussion...as of 2:24 am PST Monday...quiet weather in the
short term. Skies are mostly clear early this morning with just
some thin high clouds passing overhead. The boundary layer is dry
with dew points around 40 degrees along with some light offshore
flow. This combination should keep the Bay area essentially fog
free this morning and right through midweek. High pressure
building over the region will bring strong Santa Ana winds to
Southern California but weather for the Bay area will be tranquil
with seasonably warm afternoons from the upper 60s to upper 70s
through Wednesday. Right now Tuesday and Wednesday look to be the warmest
days this week with some lower 80s possible for the interior
valleys of Monterey County. Good travel weather with no
precipitation...Tule fog and marine layer expected to impact aviation or
auto travel plans right through Thursday.
Main weather item of interest will become the long range
forecast. Still several days out and don't want to get too
specific as daily model changes still likely to occur. Bottom
line is pretty good consensus for rain developing in the North
Bay later Friday into early Saturday with an initial weak system.
Subsequent wetter systems then prognosticated to move onshore later
Saturday into Sunday. Only fly in the ointment could be strong
southerly flow that isn't ideal for orographics. However that's
subject to change and upper jet dynamics could be quite strong.
At this time Sunday looks to be the wetter of the two days this
weekend as stronger energy moves onshore. Still not confident
enough to start advertising rain totals and specific impacts but
given the Sunday after Thanksgiving is a busy travel day those
with travel plans should follow the forecasts as travel delays
would appear likely including aviation...wet Bay area roads and
potentially significant snow over the Sierra passes.
Models augur unsettled pattern at least through the middle of
next week. Fingers are crossed for some wet weather and long
range signals are in our favor including the pna teleconnection
going negative as well as a fairly strong mjo signal moving into
phase 3 suggesting wetter than normal conditions along the West
Coast which not surprisingly is supported by the cfs v2 model as
well as the latest 6-10 and 8-14 day CPC precipitation forecasts.
Aviation...as of 9:05 am PST Monday...no major change from
previous forecast. VFR through the period.
Vicinity of ksfo...VFR.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR.
Marine...as of 08:53 am PST Monday...light to moderate northerly
flow will persist along the central coast today as a ridge of
high pressure remains overhead. Winds will become more southerly
middle week as a weak frontal system approaches the region. A
moderate west to northwest swell will impact the coastal waters
for much of the upcoming week as well.
Public forecast: rgass
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