Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service San Francisco Bay area
313 am PST Sat Dec 20 2014

Synopsis...scattered showers will continue across our area today
and slowly diminish tonight. This will be followed by a ridge of
high pressure building over the West Coast resulting in a drying
and warming trend through at least most of next week.

&& of 3:10 am PST Saturday...surprising number of
showers overnight with 12 hour rainfall totals quite a bit above
expectations. In fact...portions of Santa Cruz County are well
over an inch and on their way to hitting 1.5 inches. Current radar
loop shows bulk of activity stretching in a band from Santa Cruz
and San Mateo counties NE through Santa Clara County. Hrrr seems
to have done a fairly good job with showing the evolution and
tended to favor it for the short term forecast. It indicates that
showers will be on the decrease through the day although all
locations will have at least a shot at getting light rainfall.
Probability of precipitation were pushed up for virtually all spots and may have be
increased even more if they showers do not start to dissipate
before sunrise. In general rainfall amounts will be light today
however would not be surprised if a few locations get an
additional half an inch by tonight.

A ridge of high pressure along with warmer 850 mb readings will
start to nose into our County Warning Area tomorrow and remain in control at least
into Tuesday. This will allow for drying plus warmer readings in
all locations. Tuesday is expected to be the warmest day of the
week with highs in the 60s to lower 70s.

An inside slider will drop down Christmas evening (wednesday) mostly
impacting areas to our north and east with rain answer snow.
However...guidance continues to show the southern extent of the
moisture moving through our area especially the North Bay. The
bigger impact will be to cool off temperatures back to near normal
levels. Could also see a few inland spots dropping back into the
middle 30s.

Longer range outlook going into 2015 has drier than normal weather
forecast. Right now travel conditions from Christmas to new years
look to be good around our area.

&& of 9:48 PM PST Friday...a cold front continues to
pass over the forecast area. Precipitation is now confined to south
of the San Francisco Bay area. The front is no longer expected to
be strong enough to mix the low clouds out so expect MVFR ceilings at
most terminals overnight. Rain should end shortly in the San Jose
area but stick around until the early morning hours in Monterey.

Vicinity of ksfo...MVFR ceilings will prevail through around 1900z
Saturday. Once the clouds lift on Saturday VFR is anticipated into
the evening hours. Winds are expected to be generally light
southerly through the forecast period.

Confidence is moderate.

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...MVFR ceilings and light rain are
anticipated overnight with rain ending by sun rise. VFR is
anticipated by around 1800z Saturday.

Confidence is moderate.

&& of 3:10 am PST Saturday...a large storm in the Gulf of
Alaska has generated large long- period swells that will impact
the coastal waters through tonight. Surface high pressure will
build off the California coast tonight into early next week
resulting in increasing northwest winds over the southern waters
beginning Sunday.


Mtr watches/warnings/advisories...
... Surf advisory and coastal Flood
Advisory...all coastal locations today
Small Craft Arena to pt Reyes 0-10 nm until 3 PM
Small Craft Reyes to Pigeon pt 0-10 nm until 3 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm until 3 PM
Small Craft pinos to pt Piedras Blancas 0-10 nm until 3 PM
Small Craft Arena to pt Reyes 10-60 nm until 3 PM
Small Craft Reyes to Pigeon pt 10-60 nm until 3 PM
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm until 3 PM
Small Craft pinos to pt Piedras Blancas 10-60 nm until 3 PM
Small Craft Advisory...rough bar advisory for sf bar



Public forecast: Bell
aviation: Larry
marine: west pi

Visit US at weather.Gov/sanfrancisco

Follow US on facebook, twitter, and youtube at:

National Weather Service Glossary of Abbreviations