Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1044 am PDT Tuesday Jul 7 2015
Synopsis...look for continued widespread night and morning low
cloudiness...along with some patchy fog and local coastal drizzle.
An upper low off the coast will move inland late Wednesday.
Associated upper level moisture may produce isolated showers and
thunderstorms in the Wednesday evening through Thursday night time
frame. Temperatures through the week will generally be near
Discussion...as of 08:55 am PDT Tuesday...the marine layer
remains very disorganized compared to previous days and resulted
in less extensive cloud cover over the region this morning. The
low clouds that did develop inland overnight will likely burn-off
quickly this morning and give way to mostly sunny conditions. In
addition...temperatures region-wide are generally in the 60s this
morning and will warm into the 70s and 80s inland...while coastal
areas peak in the upper 60s to lower 70s. With that said...no
changes are needed to the short-term forecast at this time.
Previous discussion...as of 3:00 am PDT Tuesday...clouds are
returning to the coast overnight and have filtered into some of
the adjacent valley locations. Fort Ord profiler is very
interesting today and has gone from a solid 2000 feet or so the
past couple of days to a very unorganized almost mixed out layer
this morning. Will be interesting to see how it changes today. The
poorly defined marine layer is likely one of the reasons that
there are currently some breaks in the clouds. However...surface
gradient is 3 mb from the west and about 1 mb from the north so
look for clouds to make is farther inland by sunrise.
Synoptically conditions are similar to yesterday with an upper
level low to our west forecast to remain fairly stationary at
least through today. Clouds should burn-off fairly fast with sunny
conditions in most spots expected by noon. Highs will be in the
middle 60s to middle 70s at the coast with middle 70s to middle 80s for most
The upper level low will finally progress to the east and be
overhead on Wednesday. At the same time conditions will become
more unstable with lifted values forecast to lower to around zero
and MUCAPE numbers locally over 250 j/kg. Models have slightly
backed off on convection compared to previous runs however with
the position of the low and some instability present will keep the
mention of possible showers and thunderstorms going. Models do indicate
coastal drizzle both Wednesday and Thursday morning which seems
reasonable given the expected pattern.
The low will quickly lift to the northeast the second half of
Thursday leading to the end of any showers. It will then be
replaced by a longwave trough extending down most of the coast.
Precipitation is not anticipated although the trough will keep temperatures
running near normal. A few inland spots will likely be cooler than
Longer range outlook out to July 20th sows little change in the
pattern with temperatures forecast to be near normal with generally dry
Aviation...as of 10:40 am PDT Tuesday...a disorganized...but deep
marine layer impacted much of the region this morning. Most
terminals have clear...but pesky clouds remain in sf Bay impacting
koak and ksfo. Do expect these clouds to gradually erode with in
the hour. Already seeing sign on cams and satellite. VFR this
afternoon. Marine layer will roll back in tonight with IFR
conditions. Overall conf is medium to high.
Vicinity of ksfo...MVFR through 18-19z...put 1830z for ksfo taf.
VFR this afternoon with west winds gusting to 24 knots after 20z.
Ceilings return tonight around 06z.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR this afternoon. Ceilings return
shortly after 00z tonight.
Marine...as of 10:38 am PDT Tuesday...light to moderate winds
will persist along the central coast as a weak low pressure system
remains over the eastern Pacific. Winds will be gusty each
afternoon in both bays with decent onshore flow. The low pressure
system will move across the coastal waters Thursday bringing a
slight chance of thunderstorms.
... Bay from 2 PM
Public forecast: rgass/Bell
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