Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service San Francisco Bay area
1039 am PDT Wednesday Apr 23 2014

Synopsis...slightly warmer temperatures are expected today
through Thursday along with generally dry conditions. Another
storm system will then bring cooler temperatures and chances for
precipitation back to the region late Thursday night through the
start of the upcoming weekend.

&&

Discussion...as of 8:45 am PDT Wednesday...aside from some high
clouds...skies are mostly clear across the district this morning
and temperatures are running cooler than yesterday at this time by
as many as 9 degrees. With weak high pressure building over the
state today...highs today are anticipated to be slightly warmer
than those on Tuesday. The onshore flow should be less today as
the sfo-SAC surface pressure gradient is significantly weaker...1.2
mb as compared to 3.4 mb 24 hours ago.

A weak system approaching the West Coast will bring an increase in
cloudiness to northern California by tonight. A slight chance of
showers is possible across the far norther portions of Sonoma
County overnight...but rainfall amounts are expected to be light.

Rain chances will increase across northern California Thursday
night ahead of the next cold front forecast to impact the region.
Rain showers will be possible across the North Bay late Thursday
night and then spread southward Friday morning as the boundary
moves through. A deeper middle/upper level trough will then sweep
across central California on Friday. With a moderately unstable
airmass in place...thunderstorms will be possible Friday afternoon
as the main upper low center moves across. Forecast rainfall amounts
are marginal with this fast-moving system...and showers are
expected to taper off by Saturday as the flow becomes more
northerly. This will result in generally dry conditions on
Saturday before another weak disturbance moves across northern
California Saturday night. Cannot rule out a few showers across
the San Francisco Bay area northward Saturday night into early
Sunday morning...but the main effects will be much farther north.

High pressure is the prognosticated to build over the west beginning on
Monday. This will bring dry conditions and warmer temperatures to
the district. Inland valley locations will easily warm into the
80s with some areas possibly hitting the lower 90s on Tuesday and
Wednesday.

&&

Aviation...as of 10:30 am PDT Wednesday...high clouds cover the
region this morning with VFR conditions everywhere. Concern for
today will be gusty onshore flow this afternoon...but not as
strong as yesterday. Conf is high. For tonight...conf decreases
as low level moisture increases with approaching cold front. For
now...will introduce MVFR ceilings late tonight with ceilings 2-3k feet.
Will not mention any precipitation with the front.

Vicinity of ksfo...no real change from previous forecast. VFR
through tonight. Will bring ceilings tonight. West winds 15 knots will increase
to 20 knots this afternoon with gusts to 30 knots.

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...VFR through tonight with MVFR ceilings
by tomorrow morning.. the sea breeze will reach 10 to 15 knots this
afternoon with gusts to 20 knots possible.



&&

Marine...as of 10:35 am PDT Wednesday...mostly benign weather
over the coastal waters today. The one exception will be some
stronger winds associated with a coastal jet...near Santa Cruz
this afternoon and south of Point Sur. In addition...both bays
will be windy with small craft conditions. The other item of note
will a long period south swell entering the coastal waters Friday
night/early Saturday. Initially 2-3ft with a period of 20 second...then
2-4ft with a period of 18-19 second on Saturday. The south swell may get
mixed out a little bit with a moderate northwest wind and moderate northwest
swell.

&&

Mtr watches/warnings/advisories...
... Francisco Bay north of the Bay Bridge from 2 PM
Small Craft Advisory...San Francisco Bay south of the Bay Bridge from 2 PM
Small Craft Advisory...Monterey Bay from 2 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm from 2 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm

&&

$$

Public forecast: Sims
aviation/marine: mm

Visit US at www.Weather.Gov/sanfrancisco

Follow US on facebook, twitter, and youtube at:
www.Facebook.Com/US.Nationalweatherservice.Sanfranciscobayarea.Gov
www.Twitter.Com/nwsbayarea
www.Youtube.Com/nwsbayarea