Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1009 am PST Monday Dec 22 2014
Synopsis...dry and mild weather for the start of the work week as
high pressure builds over the area. Higher than average tides
will result in minor coastal flooding today and tomorrow.
Temperatures warm through midweek before a storm brushes past the
area bringing a chance of rain and cooling temperatures to near
Discussion...as of 09:05 am PST Monday...patchy dense fog and low
clouds continue to impact portions of region this morning...mainly
across the East Bay...now extending over to sfo and around the
Monterey Bay region. Conditions should slowly improve region-wide
later this morning when surface temperatures begin to warm.
Speaking of temperatures...early morning minimum temperatures are
once again a good 10 to 15 degrees above seasonal averages for
much of the region. Based off "normal" lows in the middle 30s inland
to middle 40s near the coast...the region has been experiencing low
temperatures generally in the low to middle 50s.
Once the fog and clouds burn-off later this morning...conditions
today will be mild with afternoon temperatures warming into the
middle to upper 60s. With high pressure aloft...dry conditions will
prevail through at least the first half of the work week. The
forecast looks on track this morning and no changes are needed at
Previous discussion...as of 3:20 am PST Monday...mild temperatures
continue this morning across the area with most of the region
still in the middle to upper 50s. Patchy fog and low clouds have
formed across much of the area overnight. Dense fog has been
limited to North Bay valleys and portions of the coast thus far
however. There have been a few bucket tips of drizzle as
well...mostly near the coast.
Minor coastal flooding will again be possible today along the
coastline and the Bay Shore. Perigean Spring tides...also called
King tides...will cause inundation of low lying coastal areas.
Yesterday saw some issues including roads closed in frequent
trouble spots in the North Bay and water lapping onto the
Embarcadero in San Francisco. This mornings high tide will be the
highest since August. See the coastal Flood Advisory for more
A ridge will continue to build over California for the start of
the week leading to dry weather and increasing temperatures.
Tuesday will be the warmest day of the week for most areas before
a cooler airmass begins to nudge southward.
By midweek the ridge breaks down and an inside slider digs
southeast through the western states just brushing the northern
and eastern edges of the County Warning Area. The afternoon runs of the global
models have increased the strength of the storm and have more
precipitation into the district however the NAM does not have the same
intensity. Naefs probability of measurable rain in the North Bay
has increased significantly though for San Francisco it is still
around 10 percent. For now have increased rain chances in the
North Bay and far East Bay as the system GOES by however
confidence remains low. Any rain that does fall will be very light
so the primary impact will be the cooler airmass. By Thursday
night temperatures in North Bay valleys will likely dip into the 30s.
Ridging offshore will continue through the end of the week and
temperatures remain near normal. Global models depict another
inside slider by the weekend bringing another chance of rain.
Aviation...as of 10:10 am PST Monday...main concern continues to
be low ceilings and visible across our area with satellite and surface observation
showing a mix of LIFR/vlifr up to VFR. Would expect things to
continue to improve the rest of the morning with MVFR to VFR across
the board by afternoon. Return of at least LIFR tonight into
tomorrow for most terminals due to a very moist boundary layer and
lack of wind. Winds will remains fairly light and not be a factor.
Vicinity of ksfo...LIFR to vlifr currently at sfo which should
continue at least through 19z and possibly to 20z. Conditions
forecast to improve to VFR for the afternoon through around 10z
tonight. IFR forecast to return late tonight into
Tuesday...possibly down to LIFR levels again. Moderate confidence.
Ksfo bridge approach...possible that the southern part of the
approach will scatter out a bit faster today than sfo otherwise
similar to sfo.
Monterey Bay area terminals...VFR at ksns through the day. At kmry
MVFR forecast for the rest of the morning with VFR expected at
kmry around 21z. Moderate confidence.
Marine...as of 9:05 am PST Monday...a building ridge of high
pressure along the coast will keep moderate northwesterly winds
going across most of our waters into Tuesday. Winds will decrease
by Tuesday night as the high moves into the Great Basin. Another
round of moderate northwesterly winds are expected on Thursday as
another high strengthens over the eastern Pacific.
... Flood Advisory...coastal and Bay Shore areas.
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Public forecast: rgass
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