Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
238 PM PDT Friday Sep 19 2014
Synopsis...pleasant weather is anticipated through the weekend.
A Pacific storm system will bring a possibility of precipitation
to the forecast area by middle week.
Discussion...as of 2:34 PM PDT Friday...the current visible
satellite image is showing mostly clear skies around the forecast
area this afternoon with cumulus clouds beginning to pop up over
the higher terrain south of San Jose. Under mostly clear skies
temperatures are running in the low to middle 70s at most locations with
lower 80s in the East Bay area.
The satellite water vapour image is showing yesterdays storm
system centered off of the Southern California coast which is
resulting in light north northeasterly winds over our area. These
winds are advecting drier air into the central coast...lowering
the humidity slightly. This will result in pleasant weather around
the forecast area through the weekend.
The 1200z European model (ecmwf) and gfs40 have initialized well with the current
synoptic pattern. Both models allow yesterdays storm system...low
pressure system...to linger over Southern California through
tomorrow promoting pleasant weather for the central coast. The low
pushes off into Nevada Sunday as a trough of low pressure
approaches the West Coast.
Both models remain in good agreement with this approaching trough
and a deepening low off of the British Columbia coast. This deepening low will
bring the potential for another round of rain by middle week and
cooler temperatures. Additionally...northwest winds ranging
between 45 and 50 knots off of the British Columbia coast associated with this
storm may generate the first large northwest swell of the winter
season with waves in the 10 to 15 foot range reaching the coast
Aviation...as of 11:25 am PDT Friday...clouds continuing to burn
off at this hour with VFR expected for the day into the early
evening hours. Winds will pick up through the afternoon hours.
Difficult call tonight with some guidance bringing clouds back
very early (possibly 02-03z). Moderate to high confidence through
01z. Moderate confidence after that point.
Vicinity of ksfo...VFR at least through 02z then after that some
guidance is suggesting an early return around 03z. Decided to go
Half Way between that and previous forecast with a bkn015 at 05z.
Westerly winds increase up to 20 knots after 22z. Worth noting that
satellite shows clouds just to the north and east of the Airport.
Will keep a close eye on those. Moderate confidence through 02z. Low to
moderate confidence after that.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR through the day with MVFR
forecast to return by 04z. Westerly winds generally under 10 knots.
High confidence through 03z. Moderate confidence after that.
Marine...as of 2:37 PM PDT Friday...moderate onshore winds will
continue into the evening hours. A fairly long period
southwesterly swell will continue to impact the waters into the
evening but is expected to slowly subside over the next 24 hours.
A longer period west to northwest swell is forecast to impact our
area starting on Wednesday.
... Bay north of the Bay Bridge until 9 PM
Public forecast: Larry
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