Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1043 PM PDT Thursday Jul 31 2014
Synopsis...high clouds are moving in from the west with low
clouds expected to return to the coast and in land valleys this
evening. Otherwise...the typical Summer weather pattern has
returned to the central coast with night/morning coastal low
clouds and fog stretching into the valleys and clearing skies in the
afternoon hours. Near normal temperatures and dry weather expected
through the forecast period.
Discussion...as of 8:53 PM PDT Thursday...benign weather continues
this evening and there's not too much to discuss. Middle-upper level
drying has been proceeding along as the forecast models have been
pointing to the last day or so for the Bay area and north central
coast. The precipitable water value on the evening Oak sounding is
now down to 0.56" and trending lower. Low clouds and fog persist
trapped beneath the marine inversion currently based near 1200
feet deep per area profiler data and the San Carlos sodar. The
upper level high over California will remain nearly unchanged in
strength through Friday then gradually weaken Saturday into
No forecast updates are planned this evening.
Previous discussion...as of 2:00 PM PDT Thursday...so far it has
been a mild day around the forecast area. San Rafael and sfo are
reporting current temperatures of 70 degrees and Monterey is
reporting a current temperature of 64 degrees. However...it is
warmer inland with Concord reporting 81 and Livermore 89 degrees.
Mostly clear skies are being reported are being reported around
the area. However...the current visible satellite is showing low
clouds lingering over the coastal waters and along the coast.
According to The Fort Ord profiler the marine layer is
approximately 1200 feet deep onshore winds expected overnight.
Therefore...expect a return of low clouds and fog to the coastal
and inland valleys.
The 1200z European model (ecmwf) and gfs40 have initialized well with the current
synoptic pattern and remain in good agreement through the forecast
period. Both models maintain a ridge of high pressure over the
western Continental U.S. Through the weekend with a weak upper level trough
developing along the coast by the beginning of next week. At the
surface a thermal through positioned along the coast will promote
warm seasonal temperatures inland and cool temperatures along the
Aviation...as of 10:43 PM PDT Thursday...northerly flow over the
coastal waters continues to erode the stratus along the coast.
Nonetheless patchy stratus remains anchored along portions of the
coast and latest guidance continue to bring ceilings over area
terminals overnight. Have removed ceilings out of ksts overnight...
however a sunrise surprise can not be ruled out...low confidence.
Vicinity of ksfo...VFR conditions expected through late tonight
with ceilings over koak returning after midnight if at all. Clearing
currently forecast for 17z Friday. West winds will ease overnight.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...LIFR ceilings expected through the night.
Clearing expected between 18z-19z Friday. West winds will continue
to ease becoming light and variable overnight.
Marine...as of 10:22 PM PDT Thursday...northwesterly winds will
increase over the northern coastal waters beginning tonight as
high pressure builds over the eastern Pacific. Strongest winds are
expected north of Point Reyes. These strong winds will generate
steep and choppy seas.
... Arena to pt Reyes 10-60 nm
Public forecast: canepa/Larry
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