Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
827 PM PDT Thursday Aug 28 2014
Synopsis...normal to slightly above normal temperatures and dry
weather will persist through the Holiday weekend.
Discussion...as of 8:27 PM PDT Thursday...the final low light
visible satellite image is showing low clouds banking against the
central California coast this evening. Low clouds are currently
being reported at Watsonville Airport, Monterey, Salinas and
Halfmoon Bay airports. The Fort Ord profiler shows a solid 2000
foot deep marine layer and the surface pressure gradient is
lightly onshore. Therefore...expect low clouds to return to the
inland valleys overnight.
The final low light visible satellite image also shows some middle to
upper level clouds entering the coastal waters. These clouds are
entrained tropical moisture from Tropical Storm Marie. This
moisture will move over the forecast area tomorrow but should not
result in any rain. However...the skies will be cloudier tomorrow
and it will probably feel muggy. The current forecast package
looks good so no up dates are needed this evening.
Previous discussion...as of 3:00 PM PDT Thursday...after fairly
widespread cloudiness across most of the urban areas today, clouds
have cleared and most spots are seeing sunny skies. Only exception
looks like a few patches of clouds still along the immediate
coastline. Temperatures have been running a few degrees cooler
than yesterday although highs should still up near normal values
-- 60s to middle 70s at the coast with middle 70s to upper 80s inland.
Satellite nicely shows Tropical Storm Marie churning around 900
miles to the southwest of San Francisco continuing to track to the
northwest. NHC forecast calls for it to continue to dissipate and become
Post-tropical by tonight. Closer to home, the big question of the
past week has been if any moisture associated with Marie would
become entrained in the flow and move into our County Warning Area as a longwave
trough sweeps into the pacnw. Models have been in excellent
agreement over the past three days that any rainfall would remain
well out of our area due to a ridge blocking any advance.
Although rain or showers will not make it to the coast, high
clouds along with higher humidity readings can be expected Friday
and Saturday. Highs on Friday should be close to what we see
today. Locally breezy conditions are possible especially for the
north and East Bay mountains both days due to the proximity of the
longwave trough. 925 mb speeds are only expected to be 15-25 knots so
we should be well under and advisory levels.
Quiet weather with near normal temperatures looks likely all of
the way through the upcoming weekend into the first half of next
week as the longwave trough departs well to the east while a ridge
of high pressure stays in control out over the Pacific. A dry
northwesterly flow aloft will be between the two features and over
our area. An additional longwave trough will move down from Canada
and bring cooler conditions especially for inland locations by
next Wednesday. If the operational European model (ecmwf) verifies, that trough will
stay nearly stationary through the second half of next week which
will help to keep cooler than normal readings for inland spots.
Aviation...as of 4:55 PM PDT Thursday...low clouds along the
coast are currently pushing back inland through coastal gaps and
bays. Ceilings expected to make an early return over Monterey Bay
area terminals. Bay area terminals will see a return of ceilings late
tonight. Moderate seabreeze to around 15 to 20 knots will ease this
evening and overnight.
Vicinity of ksfo...VFR conditions expected to prevail through the
late this evening. IFR ceilings expected to return after 06z tonight.
An afternoon seabreeze around 15 to 20 knots with gusts to 25 knots will
ease after sunset this evening.
Ksfo bridge approach...VFR conditions expected through late
tonight. IFR ceilings affecting the approach after 10z Friday morning.
The approach will scatter out around 18z Friday.
Monterey Bay area terminals...IFR ceilings expected to return after
00z this afternoon. West winds around 10 to 15 knots will ease
Marine...as of 2:30 PM PDT Thursday...high pressure will build
off the northern California coast on Friday resulting in
increasing northwest winds that will last through the weekend.
Southerly swell from former Hurricane Marie will gradually subside
through the end of the week.
... Arena to pt Reyes 10-60 nm from 6 am
Small Craft Advisory...sf Bay north of the Bay Bridge until 9 PM
Public forecast: Larry
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