Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1059 PM PDT Sat Aug 29 2015
Synopsis...a dry upper trough will remain anchored near the West
Coast through next week. Temperatures near the coast will be near
seasonal norms...while inland areas will generally be cooler than
normal over the next seven days. No rain is expected.
Discussion...as of 8:45 PM PDT Saturday...the southern end of a
cold front dissipated as it moved into the San Francisco Bay area
today. This front produced some light rain across the northern
portion of our forecast area early today. Most locations picked up
just a few hundredths. Sea Ranch on the Sonoma County coast
received the most rainfall with 0.12". The airmass ahead of this
front was warm and muggy...but much cooler and drier air has been
spreading over our area behind the front today. High temperatures
today were as much as 20 degrees cooler compared to yesterday. The
biggest temperatures falls occurred on the San Francisco peninsula
and in the East Bay valleys.
Early evening temperatures and surface dewpoints are generally
running several degrees below what they were at the same time
last evening. Thus...we can expect more comfortable sleeping
conditions tonight compared to the past couple of nights.
Skies remain mostly clear this evening...although a few patches of
low clouds have formed along the North Bay coastline. The low
levels remain relatively well-mixed...and so coastal low clouds
will probably remain rather patchy overnight. Most areas should
remain mostly clear through the evening hours...allowing for a
good look at the "super moon".
After some patchy morning low clouds...Sunday is expected to be a
mostly sunny and mild day with brisk onshore breezes.
The models have been consistently holding the longwave trough
position near the West Coast through next week. Temperatures near
the coast probably won't vary much through the week...and will be
close to seasonal norms. Inland temperatures are likely to climb slightly
on Sunday and Monday as the airmass aloft warms a bit. Cooler
conditions will then develop inland by midweek as the trough
deepens along the coast and cooler air moves in from the
northwest. Although the trough is forecast to deepen around
midweek...the medium range models agree that moisture will be
lacking and precipitation won't make it much farther south than the
The upper trough is forecast to shift to the east late in the
week...which should result in warmer weather by next weekend.
Aviation...as of 10:54 PM PDT Saturday...drier air on west-northwest
surface winds continues to move in over the entire area. Satellite
shows some patchy stratus developing over Sonoma and Marin counties
and over northern San Mateo County. Much drier air will also sweep
in from the west tonight within a deeper layer of the atmosphere
resulting in increased radiational cooling. Because of this expect
additional stratus and fog patches tonight into Sunday morning.
Clearing skies expected by middle-late morning Sunday.
Vicinity of ksfo...tempo broken MVFR ceiling forecast tonight...MVFR ceiling
prevailing 11z-17z. VFR is very likely to return middle-late Sunday
morning. West winds 20 gusts to 28 knots forecast 21z Sunday to
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...drier air is moving in on west-northwest winds.
It's mostly clear to clear around the area per satellite and
observations. Localized IFR possible tonight...coverage should be
at a minimum. VFR likely Sunday.
Beaches...as of 10:45 am PDT Saturday...a long period west swell
has arrived and will continue to advance on west facing beaches
through the weekend and into early next week. These long period
swells can produce hazardous rip currents that can quickly pull
swimmers out to sea. The highest risk of hazardous conditions will
be this weekend when onshore winds weaken and the period increases
from 15 to 18 seconds. Swimmers caught in a rip current should
swim parallel to the coast to escape the rip currents.
Marine...as of 9:53 PM PDT Saturday...northwest winds will
increase over the coastal waters through the weekend. Gusty west
winds are forecast Sunday afternoon and evening over the northern
San Francisco Bay. A long period west swell will continue to move
through the waters through the weekend and into early next week.
... Pinos to pt Piedras Blancas 0-10 nm
Public forecast: dykema
Visit US at www.Weather.Gov/sanfrancisco
Follow US on facebook and twitter at: