Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
853 PM PDT sun Sep 14 2014
Synopsis...a minor cooling trend back to more seasonable
temperatures will continue Monday and Tuesday as onshore flow will
become established with a weak trough offshore. A stronger system
will approach far northern California by Wednesday bringing a
slight chance of showers to the North Bay later Wednesday into
Thursday. That system will eventually cut off over central
California but another ridge will build over the Bay area and
northern California by next weekend and beyond.
Discussion...as of 8:52 PM PDT Sunday...skies are now mostly
clear to clear over the region. A few high clouds are drifting
eastward over the eastern Pacific ahead of an upper level low
pressure area located approximately 800 miles west of San
A new trough from the Gulf of Alaska will move southeast and merge
with the aforementioned epac upper low pressure area then move east
to California by mid-week. The low pressure area will bring a chance
of light rain to the Northern Bay area Wednesday night and
Thursday. The newest 00z NAM model shows very light quantitative precipitation forecast arriving
Wednesday night with very light quantitative precipitation forecast Thursday morning as far south
as San Mateo County. Rainfall amounts overall look to be light
generally under a 1/10 inch.
Plenty of tropical moisture with the remnants of "odile" will
move northeast into northern Mexico and eventually the Desert
Southwest this week.
Forecast uncertainty in the extended is moderate to high. By next
week the European model (ecmwf) and GFS show increased upper level ridging developing
over California. The Gem model differs in solution showing an upper level
trough moving off the eastern Pacific.
Aviation...as of 5:00 PM PDT Sunday...clear skies will prevail
across the region through late tonight with ceilings expected to
return well after midnight over Bay area terminals. Monterey Bay
area terminals will likely maintain VFR conditions until after 05z
tonight. The marine layer persist around 1000 feet this afternoon
and is expected to deepen overnight as an upper trough off the
coast approaches the region. Moderate onshore flow will ease this
evening becoming light overnight.Moderate confidence.
Vicinity of ksfo...VFR conditions will continue through late
tonight. Ceilings anticipated to return after 12z. Moderate west
winds around 15 to 20 knots will ease this evening to around 5 to 10
knots overnight. Moderate confidence.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR conditions will continue through late
this evening. Ceilings anticipated to return around 05z. West winds
around 10 knots will ease overnight becoming light and variable.
Marine...as of 2:05 PM PDT Sunday...generally light onshore flow
and gentle seas will continue through much of the upcoming work
week. Meanwhile...a long period southwest swell will begin to
build into the waters and continue through midweek.
... Bay north of the Bay Bridge until 9 PM
Public forecast: canepa
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