Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1033 PM PDT Tuesday Sep 2 2014
Synopsis...dry conditions will persist through the period along
with temperatures near or slightly below normal. Overnight clouds
can be expected in most locations.
Discussion...as of 8:57 PM PDT Tuesday...temperatures cooled
across the board today in response to a deepening marine layer
and onshore flow that brought cool marine air well inland.
Temperatures dropped anywhere from a 5 to 15 degrees in most
locations to as much as 25 degrees in the North Bay. Widespread
low clouds are expected to penetrate well inland again tonight
under a 2000+ feet marine layer. Patchy drizzle is also expected
along the coast overnight.
Temperatures will cool a few degrees Wednesday as 850 mb temperatures cool
a degree or two and 500 mb heights drop from 588 dm to 580 dm.
Persistent onshore flow and low clouds along the coast will also
aid in keeping temperatures cool.
Models are in fairly good agreement with the upcoming pattern
change. As the week progresses an upper trough currently swinging
through the Pacific northwest is expected to pull eastward. The
trough is prognosticated to stretch across northern California and
persist there into the weekend. Only minor fluctuations in
temperatures are anticipated through the end of the week and into
the weekend while the pattern remains fairly stationary. Onshore
flow and a deep 2000+ feet marine layer will continue through the
For next week the European model (ecmwf) build a ridge of high pressure back into
our area with guidance suggesting another round of above normal
Aviation...as of 10:20 PM PDT Tuesday...coastal stratus continues
to move steadily inland this evening. There'll be some extra patchy
drizzle to accompany the clouds overnight. Generally expecting
widespread stratus coverage Wednesday morning with partial
clearing back to the coast by early afternoon. Weather conditions
will remain favorable for another stratus intrusion Wednesday
evening into Thursday morning.
Vicinity of ksfo...ASOS reports few007 sct013 at 10 PM local. Stratus
cloud cover expanding around the Bay is expected to fill in at the
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...IFR tonight. Clearing forecast by 18z
Marine...as of 10:20 PM PDT Tuesday...northwest winds will remain
gusty over the northern outer waters tonight and Wednesday.
Elswhere northwest winds will be at lighter speeds as a trough
develops near the California coast.
... Arena to pt Reyes 10-60 nm
Public forecast: CW
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