Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
527 PM PST Friday Dec 19 2014
Synopsis...scattered showers can be expected through the evening
hours with a few forecast to linger into Saturday especially north
of San Francisco. 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.
Discussion...as of 3:00 PM PST Friday...radar shows that the
moderate to heavy rain we had earlier over the North Bay has
slowly shifted to the south and dissipated through the afternoon.
For what appears to be a non-event...rainfall amounts have been
surprisingly robust over the North Bay with a few stations picking
up than 2 inches since midnight. Urban locations have also
benefited with San Francisco picking up nearly an inch in the
period. Additional amounts should be light although would not be
surprised if portions of Santa Cruz and Santa Clara counties pick
up a quarter of an inch or more into the evening hours. Most spots
in Monterey could will likely come in with smaller values --
generally up to 0.15 inches. A few showers will continue into the
overnight hours with light amounts forecast.
For the upcoming weekend drier weather with some warming can be
expected as a ridge of high pressure nudges into our County Warning Area and the
storm track heads back to our north. Guidance continues to show
possible showers especially for the North Bay on Saturday although
any additional amounts should be light -- generally under a tenth.
Clouds will also be on the decrease and should allow for some
peaks of sunshine especially from Santa Cruz County to the south.
By Sunday most locations will be back in the 60s.
Additional warming is forecast for Monday and Tuesday as the ridge
builds just off our coast and 850 mb temperatures increase. Tuesday
should be the warmest day for next week with 60s to lower 70s in
the cards. Possible a few isolated middle 70s will appear in southern
For Wednesday -- Christmas evening -- an inside slider will drop down
into the pacnw/norcal region and eventually head into southern
Nevada Wednesday night. As the system drops down it will mostly
bring cooler air with it however a few showers may be triggered
especially over the North Bay. Probability of precipitation were pushed up for this period.
For the rest of next week a dry and seasonably cool northwest flow will
remain in place. Latest 8 to 14 day outlook through January 2nd
also favors drier than normal weather which will help to make
travel easier for those on the roads during the Holiday season.
Aviation...as of 5:27 PM PST Friday...a cold front is passing
over the forecast area this evening bringing showers and MVFR ceilings
along for the ride. The trailing edge of the front is just passing
by ksfo heading south towards San Jose and eventually Monterey.
Behind the front expect showers to become more isolated ending
shortly after midnight. Drier weather is anticipated Saturday as
high pressure builds in over the California coast.
Vicinity of ksfo...MVFR ceilings and lingering showers will prevail
through at least 0600z. Showers will taper off overnight with VFR
and drier weather expected Saturday.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...MVFR/VFR ceilings are anticipated this
evening as a cold front continues to pass over the forecast area.
Showers should stick around through at least midnight.
Marine...as of 3:00 PM PST Friday...a coastal trough will
continue to push onshore Friday evening ahead of a building high
pressure ridge. Southerly winds up to 20kts will prevail prior to
the frontal passage then turn light and veer towards the northwest
in the wake of the passage. Northwest swell prevails through the
forecast period. Northwest swell in excess of 15 feet possible over the
open ocean 10nm or more offshore through early Saturday. Hazardous
seas over the ocean and near the coast for much of the weekend. On
the horizon... north winds increase early next week.
... Surf advisory...the coastline from Sonoma County south
through Monterey County.
Small Craft Advisory...pt 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 pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
Small Craft Advisory...rough bar advisory for sf bar from 10 PM
Public forecast: Bell
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