Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
652 PM PST Sat Dec 3 2016
Synopsis...dry weather conditions will persist through the
weekend along with a slight warming trend in daytime temperatures
today. Meanwhile, overnight conditions will remain chilly under
mostly clear skies. A region-wide cool down is forecast for the
first part of next week as a dry cold front pushes through the
region. Rain chances develop later next week.
Discussion...as of 01:35 PM PST Saturday...upper level ridging
and offshore flow has led to another sunny day around the Bay
area. After a chilly start, temperatures did warm into the 50s
and 60s this afternoon. In fact, a few spots are actually running
warmer than 24 hrs ago. Did a minor update to increase a few spots
this afternoon for Max temps.
For tonight, clear skies remain leading to another night of chilly
temperatures. Winds will be breezy again, but mainly in the hills
where protected valleys will be light or calm. Those protected
valleys will be the coldest spots with lows in the 20s/30s with
High pressure weakens on Sunday as a weak cold front moves in from
the north. Models continue to produce light precip, but north of
the Bay area. Therefore, will keep the forecast dry but increasing
clouds seems more likely. Behind the frontal boundary cooler air
will move in over the region. Temperatures on Monday will see a
noticeable cool down with temps mostly in the 50s during the day
and 30s/40s at night (protected valleys in the 20s). The cooling
trend continues Tuesday and Tuesday night. Latest forecast
indicates widespread 30s with interior 20s by early Wednesday
morning. If the current forecast pans out it could be the coldest
morning of the season yet.
A pattern shift by late Wednesday into Thursday as a trough
approaches the region. Medium range models continue to indicate
possible precip by early Thursday initially over the North Bay
then spread southward. Current forecast mentions this and see no
reason to change it at this time. It is still 5-6 days out and
conf remain low. For what it is Worth long range models hint
another system next weekend.
Aviation...as of 6:52 PM PST Saturday...a strong mid-upper level
ridge is resulting in stable weather and a generally continued dry
air mass, however surface dewpoint temperatures in the upper 30s
to upper 40s have trended higher everywhere since yesterday at
this time. Weak surface pressure falls from the Bay area to north
central coast recently observed while a surface ridge over far
northern California gradually weakens into Sunday morning; a
moderate northerly pressure gradient kacv-ksfo and kuki-ksts is
likely to persist at least this evening.
Moderate to high confidence VFR for most of the forecast area
tonight and Sunday exceptions being model guidance is forecasting
fog /IFR to vlifr/ later tonight and Sunday morning at ksts, and
kapc may see at least thin fog tonight per guidance. Khaf presently
reports 4 miles visibility in fog and broken cig 300 feet.
Vicinity of ksfo...VFR. Northwest-west wind 10 knots or less tonight becoming
light NE Sunday morning. West winds near 10 knots Sunday.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...surface winds becoming light southeast this
evening. West-northwest winds near 10 knots Sunday.
Marine...as of 5:12 PM PST Saturday...gusty NW winds will continue
overnight into Sunday as a dry cold front approaches Sunday afternoon
and evening. Large and long period NW swells will continue through
the weekend as well. Persistent NW winds will continue into early
next week with subsiding swells but large wind waves.
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm until 2 am
Public forecast: mm
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