Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1029 am PDT Thursday Aug 21 2014
Synopsis...warmer temperatures are expected away from the coast
the next few days. Otherwise little change is forecast through the
weekend with continued below normal temperatures expected...especially
for inland areas. Much warmer inland temperatures are possible by
the middle of next week.
Discussion...as of 08:30 am PDT Thursday...widespread low clouds
again this morning. The marine layer depth is down to around 2100
feet so clouds should be a bit quicker to burn off this morning.
Southerly flow persists bringing most of the stratus into the North
Bay while leaving the Santa Clara Valley mostly clear.
Temperatures are currently a couple of degrees cooler than at this
time yesterday morning however the increased clearing this
afternoon will lead to several degrees of warming inland. Forecast
calls for similar weather to continue into the weekend and is on
track...no major updates are anticipated this morning.
Previous discussion...as of 3:00 am PDT Thursday...southerly flow in the
low levels has caused stratus to pile up in the North Bay this
morning. Local drizzle is possible in these areas during the early
morning hours. The marine layer is steadily compressing as upper
low over Southern California moves east and upper level high
over the eastern Pacific nudges into the state. This will allow
for more afternoon clearing and about 4-8 degrees of warming inland
on Thursday. Another upper trough will deepen over the Pacific
northwest tonight and Friday and will maintain a marine layer of
1500-2000 feet over the area. Upper level troffing will continue
over the Pacific northwest through the weekend behind the
original upper trough. As a result temperatures will cool off
slightly Friday through Sunday and be near or slightly below normal.
Previous model runs suggested significant warming around next
Tuesday as upper level high from the eastern Pacific moves
over the state. The latest models maintain this scenario except
the European model (ecmwf) holds off the heating until Wednesday. So the extended
forecast still calls for several degrees of warming for the
middle of next week.
Aviation...as of 10:30 am PDT Thursday...as forecast, clearing
happened earlier today although still seeing MVFR to IFR ceilings
across Napa/Sonoma which should burn off shortly. Looking for VFR
for the afternoon into the early evening hours for all terminals.
Sea breeze winds also expected to ramp up 20z-02z. Models in good
agreement for a late return for MVFR ceilings for most areas tonight.
Moderate to high confidence.
Vicinity of ksfo...VFR through the day with winds 280-300 gusting
up to around 20 knots from 21z to 02z. Late return of stratus
expected tonight -- possibly after 11z. High confidence through
02z. Moderate to high confidence on the return for tonight.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR through the day with winds
240-280 up to 12 knots. Return of MVFR ceilings after 02z although
possible they could be later than that time. High confidence
through 0z. Moderate confidence after that.
Marine...as of 3:00 am PDT Thursday...a weak surface pressure
gradient will maintain generally light winds across a majority of
the coastal waters today. Moderate winds are expected over the
northern outer waters. The surface pressure gradient is expected
to increase Friday...resulting in strengthening winds. A moderate
period southerly swell generated by tropical storms will move into
the region later this week.
... Bay north of the Bay Bridge from 2 PM
Public forecast: ac/west pi
Visit US at weather.Gov/sanfrancisco
Follow US on facebook, twitter, and youtube at: