Scientific Forecaster Discussion
Area forecast discussion...corrected aviation discussion
National Weather Service San Francisco Bay area
1012 PM PST Sat Feb 13 2016
..warm weather to return Sunday through Tuesday...
Synopsis...high pressure will strengthen over California during
the next few days. Record high temperatures are possible early in
the week. On Wednesday temperatures will cool as a trough
approaches with rain becoming likely Wednesday night into
Thursday. Showers will end by Thursday afternoon...with a return
to dry weather Friday through next weekend.
Discussion...as of 9:00 PM PST Saturday...patchy low clouds and
fog near Monterey Bay finally cleared by late afternoon. Skies
remain clear across the entire forecast area this evening except
for some thin high clouds overspreading the sf Bay area. Drier air
has begun to mix into the boundary layer...particularly in the
North Bay where northerly winds have picked up and surface
dewpoints are up to 13 degrees below what they were 24 hours ago.
Further south...enough moisture remains in the low levels for
patchy fog and low clouds to develop overnight...primarily near
Monterey Bay. Where fog does develop later tonight...it will
probably be dense.
An upper level ridge is forecast to build just offshore tonight
and Sunday...with 500 mb heights forecast to reach 585 dm by late
Sunday. Subsidence under this ridge will push 850 mb temperatures up to
14 degree c by Sunday afternoon and as high as 16 c by late Monday.
At the same time...surface high pressure building to our north and
east will generate moderate offshore flow...bringing drier air
into our region. These developments will allow temperatures to
climb over the next three days...with highs forecast to be
anywhere from 10 to 20 degrees warmer than normal. At least a few
daily record high temperatures are likely. Temperatures will likely peak
in the North Bay valleys on Sunday and Monday when northerly flow
will produce the best downslope conditions. Warmest temperatures near the
coast will probably be on Monday when offshore flow will be most
robust. Elsewhere...warmest temperatures will be on Monday and Tuesday.
North to northeast winds will increase in the hills tonight and
become locally strong and gusty over the higher ridges and peaks
by late tonight. Breezy conditions in the hills are then expected
to continue on through Monday. Local gusts up to 40 miles per hour are
possible in the hills from late tonight through Monday...but
widespread Wind Advisory conditions are not expected. Gusty
northerly winds will mix locally down to near sea level at
times...particularly near coastal canyons at night and in the
valleys during the daytime hours. But for the most
part...strongest winds are expected to be confined to the hills.
The models continue to show a Pacific storm system of moderate
intensity moving through northern and central California from late
Wednesday through Thursday morning. There appears a reasonably
good chance that our region will see widespread rainfall from this
system. However...the models currently indicate that the best
moisture and dynamics with this system will be out of phase...with
the greatest moisture focused well south of our area and away from
significant dynamics. Thus...most model output indicate our area
will see only light to moderate amounts of rainfall...generally
from 0.25" to 0.75". The midweek system may be our last shot at
precipitation of any significance for the next ten days as the
longer range models forecast the ridge to redevelop by next
weekend and into the following week. And...rain chances look bleak
even beyond ten days given the 12z GFS ensemble mean holds the
ridge position near the West Coast through the end of February.
Aviation...as of 10:12 PM PST Saturday...cirrus clouds well south
of a strong jet stream entering the Pacific northwest continue to spill
into the forecast area this evening. Strong northerly gradients
will continue into Sunday...uki-sts gradient is presently 2.2 mb
and sfo-sba 7.5 mb.
Vicinity of ksfo....moderate to high confidence VFR.
Sfo bridge approach...similar to ksfo.
Monterey Bay area terminals...moderate to high confidence VFR. A
few fog patches are possible nearby either late tonight and/or
early Sunday morning.
Climate...here is a list of record high temperatures from Sunday
February 14 through Tuesday February 16. The record high is listed
for each day along with the year the record was set (if the record
was set on more than one year...the most recent year is listed).
Sunday Monday Tuesday
location Feb 14 Feb 15 Feb 16
San Francisco Bay area...
Kentfield 84/1930 79/1930 77/1930
San Rafael 78/1977 78/1977 77/1977
Napa 81/1930 81/1943 81/1930
San Francisco downtown 78/1930 76/1930 75/1930
San Francisco Airport 74/1977 75/2015 69/2007
Oakland museum 80/1977 80/2015 75/2015
Oakland Airport 72/2013 73/1977 73/1977
Richmond 77/1977 75/1977 75/2015
Livermore 79/1977 80/1933 78/1977
Moffett field 82/1977 79/1977 73/1977
San Jose 80/1930 80/1930 78/1930
Gilroy 80/1996 81/1991 81/1977
Monterey Bay area...
Monterey 81/1943 79/1977 73/2013
Santa Cruz 82/2015 82/1916 85/1930
Salinas 83/2015 81/2013 80/1977
Salinas Airport 84/2015 81/2015 77/2013
King City 85/1977 86/1977 90/1977
Marine...as of 9:23 PM PST Saturday...strong high pressure located
over the eastern Pacific will build over northern California
through the Holiday weekend. As a result gusty northwesterly to
northerly winds are expected over the coastal waters with lighter
winds over the bays. A chance of rain with a frontal system will
move east over the area late Wednesday night into Thursday morning
of next week.
... 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 Arena to Pigeon pt 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Public forecast: dykema
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