Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Francisco Bay area
429 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.

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Discussion...as of 04:10 am PDT Wednesday...weak ridging is
forecast to build aloft today through Thursday afternoon and
result in slightly warmer daytime temperatures. Onshore flow will
keep temperatures coolest along coastal locations while inland
areas of the central coast warm into the lower 70s. A slight
chance of precipitation will continue across the North Bay tonight
as a weak impulse moves through northern California. However...no
measurable rainfall is expected with this system.

Rain chances increase across northern California Thursday night
ahead of the next cold front to impact the region. Rain showers
will be possible across the North Bay late Thursday night and then
spread southward through Friday morning and the boundary moves
through. A deeper middle/upper level trough will then sweep across
central California on Friday. With a moderately unstable air mass
in place...embedded thunderstorms will be possible by late Friday
morning through the afternoon hours as the main upper level
support pushes through. Having said that...forecast models keep
rainfall amounts marginal with this fast moving system. Moisture
advection becomes limited by Saturday as winds aloft become 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 as this system passes
Saturday night into early Sunday morning.

Forecast models are then in good agreement in amplifying a
middle/upper level ridge along the West Coast Monday through
Wednesday of next week. This will result in much warmer daytime
temperatures for the start of the upcoming work week. Inland
valley areas will likely warm into the middle/upper 80s with typical
warm spots peaking out around 90 degrees during the afternoon
hours Tuesday and Wednesday. Will also maintain dry conditions for
the region during this time frame given the upper level ridging.

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Aviation...as of 4:28 am PDT Wednesday...high clouds are passing
over the forecast area this morning with clear skies being
reported below 12000 feet. Yesterdays strong northerly winds have
dried the atmosphere out sufficiently enough to prevent any low
clouds or fog from forming this morning. Low clouds may be an
issue Thursday morning but mostly clear skies are expected at the
terminals in the meantime. Gusty onshore winds may be an issue
again this afternoon.

Vicinity of ksfo...VFR is expected to persist through 1000z
Thursday morning. West winds 15 knots will increase to 20 knots this
afternoon with gusts to 30 knots.

Confidence high

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...VFR is expected to persist through
the next 24 hours. The sea breeze will reach 10 to 15 knots this
afternoon with gusts to 20 knots possible.

Confidence high

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Marine...as of 04:19 am PDT Wednesday...generally light
northwesterly winds are expected across the northern coastal
waters through at least Friday morning. Moderate winds are
expected across the southern coastal waters with the strongest
winds anticipated to occur south of pt sur. Winds will increase
across the entire coastal waters Friday as a storm system
approaches the coast. A long period south swell will impact the
region late this week and over the weekend.

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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: rgass
aviation/marine: Larry

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