Scientific Forecaster Discussion
fxus66 kmtr 290559
Area forecast discussion
National Weather Service San Francisco Bay area
1059 PM PDT Wed Jun 28 2017
Synopsis...seasonable Summer pattern in place with a marine layer
along the coast leading to areas of night and morning low clouds
followed by sunny afternoons away from the coast right through the
4th of July Holiday.
Discussion...as of 9:00 PM PDT Wednesday...upper level trough
over the western US with upper level ridge off the West Coast.
West to northwest flow over the district with a solid marine
layer just under 2000 feet. This will allow low clouds to spread
into the sfo Bay area tonight. Slightly warmer temperatures are
expected away from the coast Thursday and Friday as the upper
level ridge moves over the area and compresses the marine layer.
An upper level trough will move through the area Friday night
which will deepen the marine layer. The NAM model shows
measurable drizzle along the coast Saturday morning. This makes
sense given that the upper trough will be over US at that time.
Temperatures will be cooler Saturday and Sunday. Drizzle is less
likely Sunday morning as the trough will have moved to the east.
An upper level high will build over the southwestern US early
next week bringing above normal temperatures to the inland areas.
This ridge will initially be positioned over the 4 corners area so
heatwaves are not expected during the 4th of July Holiday.
However by late in the week the GFS shifts the high northwest
which would bring very warm temperatures to the district. The
European model (ecmwf) does not show this as it keeps the high further east. So
will have to monitor for possible heat concerns late next week.
Aviation...as of 10:47 PM PDT Wednesday...for 06z tafs. A
moderate northerly gradient continues across the region and has
kept the north coast mostly clear of low clouds. The marine layer
is currently around 1800 ft and will only see minimal
fluctuations. Low clouds will fill in across area terminals as the
night progresses. Moderate onshore flow around 10 to 15 kt with
locally higher gusts will gradually ease overnight.
Vicinity of ksfo...MVFR cigs will lower to IFR around 800 feet
after 09z tonight. Low clouds will scatter out around 17z-18z
Thursday morning. Moderate west winds around 10 to 15 kt with
gusts to around 20 kt will gradually diminish overnight.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...IFR cigs will lower to LIFR overnight.
Low clouds will scatter out around 18z-21z Thursday morning.
Light west winds around 5 to 10 kt will prevail through the night.
Marine...as of 8:59 PM PDT Wednesday...building high pressure
off the California coast will maintain strong and gusty northerly
winds through the remainder of the week and into the upcoming
weekend. Steep wind waves and fresh swell will dominate the
coastal waters as a result of the strong winds. Persons operating
small crafts should use extra caution along the central California
coast and bays through at least the forthcoming weekend.
... Pt to pt pinos 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm until 3 am
Public forecast: west pi
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