Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
858 PM PDT Monday Oct 20 2014
Synopsis...dry weather conditions will return Tuesday and
Wednesday as an upper level trough moves inland. The next storm
will bring a chance of rain to the North Bay Thursday. Another
system will bring a chance of rain to most of the district Friday
night or Saturday.
Discussion...as of 9:00 PM PDT Monday...a weak frontal boundary
brought clouds and light precipitation to the sfo Bay area and the
North Bay today. Up to one-quarter inch of rain fell in the North
Bay coastal and mountain areas with less than one-tenth of an inch
in the North Bay valleys and sfo Bay area. Elsewhere scattered
light rain or mist occurred as far south as the mry Bay area.
Temperatures were generally 5-10 degrees cooler than yesterday.
An upper level trough has moved into northern California this
evening and skies are clearing behind it. Patchy low clouds will
form near the hills tonight but Tuesday and Wednesday are looking
like mostly sunny and warmer days as the next storm moves into the
Pacific northwest. This system could sag far enough south to bring
a chance of rain to the North Bay Thursday and Thursday night. However
any precipitation will be light as most of the rain will fall over
Oregon and northern California. Elsewhere it will be partly cloudy
and a little cooler Thursday.
An upper level low is forecast to deepen along 140w on Friday
bringing a chance of rain to the district Friday night or
Saturday. While rain chances are improving there are differences
in the models as to how much rain there will be. The GFS shows a
more organized system moving through the area with up to 2 to 4
inches in the North Bay hills and 1/4-1/2 inch in the southern
part of the district. The European model (ecmwf) splits the system and thus is
drier. Will continue to monitor the latest forecast model output
in the coming days to see if they become better aligned.
Aviation...as of 4:55 PM PDT Monday...condidtions will steadily
improve this evening behind the departing cold front that moved
through the region earlier today. Winds will ease overnight
becoming light and locally variable across most terminals. Patchy
low ceilings possible tonight over some terminals...otherwise mostly
clear. High confidence.
Vicinity of ksfo...VFR conditions expected across area terminals
tonight with patchy low clouds possible early Tuesday morning.
Moderate winds will ease overnight becoming light and locally
Ksfo bridge approach...similar as ksfo.
Monterey Bay area terminals...VFR conditions expected through most
of the night with MVFR ceilings possible tonight over kmry. Moderate
winds will ease overnight becoming light and locally variable
Marine...as of 02:35 PM PDT Monday...a weak frontal system
continues to move through the southern waters. Light southerly
winds ahead of the front will turn northwest this afternoon and
increase overnight...particularly south of Point Sur. Large
northwest swell is starting to move into the coastal waters and
will persist through Tuesday.
... Bar advisory for sf bar
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Public forecast: west pi
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