Scientific Forecaster Discussion
fxus66 kmtr 260504
Area forecast discussion
National Weather Service San Francisco Bay area
1004 PM PDT sun Jun 25 2017
Synopsis...look for continued cooling inland through Monday as
the ridge of high pressure that had been overhead continues to
progress to the east. Also areas of night and morning low clouds
and fog followed by sunny afternoons can be expected. Modest
warming is expected during the second half of the week, however
highs will fall well short of the recent heatwave.
Discussion...as of 07:08 PM PDT Sunday...the cool down continued
this afternoon across locations that experienced very hot
conditions late last week. High temperatures dropped 6 degrees
from yesterday to today in Concord (88 to 82), 5 degrees in
Livermore (85 to 80), and even 4 degrees in San Jose (78 to 74).
These highs translate to values that are about 2 to 8 degrees
below late June climatological normals -- a rather drastic change
from several days ago when these same locations were 15 to 25
degrees above normal. Most of the coastline along and north of
Half Moon Bay managed to remain overcast through the entire day
while the marine stratus was able to mix out throughout Monterey
Bay. Do expect the overcast skies to return later tonight for most
coastal areas with the marine layer sitting around 1,500 ft per
The Fort Ord profiler. A weak shortwave trough will push through
northern California and Oregon through tomorrow and will allow for
interior temperatures to drop another few degrees for Monday
The current forecast remains on track and no major updates
planned this evening. Please refer to previous discussion for
Previous discussion...as of 2:00 PM PDT Sunday...as expected
temperatures are running cooler than yesterday especially for
inland locations. Overall looking at a drop of 4 to 9 degrees away
from the coast with temperatures close to saturday's values.
Synoptically the strong high pressure ridge aloft has continued to
progress to the east while a more pronounced onshore flow is
setting up. Look for a quick return of the clouds this evening
along with patchy drizzle.
The ridge will continue to move to the east on Monday while 850 mb
temperatures drop another 2c down to the 19-21c range. Highs end
up being another 2 to 5 degrees cooler in most locations -- 70s to
mid 80s inland with mostly 60s at the coast. The only real
exception will be far southern Monterey and san bentio counties
where highs will still reach the 90s. Conditions on Tuesday will
A ridge of high pressure will attempt to rebuild into our region
starting Wednesday which will help to increase temperatures a bit,
however values will stay well below the very high numbers we had
recently. Generally look for 60s to lower 70s at the coast with
mid 70s to near 90 inland.
Longer range guidance through July 9th favors dry conditions with
temperatures near to a bit above normal.
Aviation...as of 10:04 PM PDT Sunday...the marine layer will
likely deepen tonight and Monday as lower level cooling develops
and persists. Stratus will need time to redevelop after mixing out
over much of the coastal waters earlier this evening. Depending
on how much stratus cigs redevelop onshore winds will bring it
back inland tonight with clearing back to the coastline Monday.
Vicinity of ksfo...MVFR cig has mixed out, low confidence on
timing its redevelopment tonight. IFR is possible Monday morning.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...IFR cigs developing later than previously
forecast due to stratus mixing out earlier this evening. Clearing
returns 16z-17z Monday. Stratus possibly returning Monday evening.
Marine...as of 9:58 PM PDT Sunday...surface high pressure will
remain located over the eastern Pacific. Northwest winds will be
locally gusty along the immediate coast. A dominant southerly
swell will persist into Wednesday morning.
... Pinos to pt Piedras Blancas 0-10 nm
Public forecast: Rowe/Bell
Visit US at www.Weather.Gov/sanfrancisco