Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
151 PM PDT Sat Aug 29 2015
Synopsis...dry weather conditions along with temperatures near or
slightly below seasonal averages can be expected through much of
the upcoming work week.
Discussion...as of 01:50 PM PDT Saturday...the weak frontal
boundary that pushed into the region this morning continues to
shift inland at this hour. Early morning precipitation over the
North Bay and parts of the Bay area has generally come to an end
as a drier air mass filters in over the region in wake of the
frontal passage. While temperatures this afternoon are cooler
compared to previous days...warm and muggy conditions continue
over a good portion of the region as low level moisture pooled
along/ahead of the cold front.
Drier and cooler conditions will persist through the remainder of
the weekend and into much of next week as a result of a long-wave
trough over much of the West Coast. Meanwhile...a series of
disturbances will drop southeastward into the Pacific northwest
and reinforce the trough though late next week. However...dry
weather conditions are forecast to persist over our region with
limited moisture aloft. Near the surface...do expect the marine
layer to return as early as tonight and bring night/morning
coastal stratus to the region along with persistent onshore flow.
Overall...dry weather to continue with temperatures at or slightly
below seasonal averages.
Aviation...as of 10:45 am PDT Saturday... chaotic skies with
varying and intermittent flight rules this morning. Latest metars
reporting mixing out and lifting of ceilings throughout the lower
layers... which will transitions ceilings from MVFR to VFR through the
next hour or two. Skies will clear behind the front... which is
pushing into the inland Northern Bay area now. Increasing clouds
for the southern taf sites...increase kmry...ksns...kwvi as front
approaches... however expecting VFR for these sites for remainder
of daylight. Return of marine layer tonight will be slightly later
than average... and with ceilings lower than normal on average. For
tonight... MVFR ceilings expected for Bay area... IFR ceilings for
Monterey Bay area. Overall confidence moderate.
Vicinity of ksfo...gradually improving ceilings... clearing rapidly
behind front. Clearing ceilings no later than 20z. Layer returns after
Ksfo bridge approach...similar to ksfo... slightly later clearing.
Posbl as late as 21z.
Monterey Bay area terminals... chaotic skies through the day as
front approaches... however ceilings should predominately be VFR with
some brief MVFR ceilings (above 2000 ft) posbl through the day. Marine
layer returns behind the front.
Beaches...as of 10:45 am PDT Saturday...a long period west swell
has arrived and will continue to advance on west facing beaches
through the weekend and into early next week. These long period
swells can produce hazardous rip currents that can quickly pull
swimmers out to sea. The highest risk of hazardous conditions will
be this weekend when onshore winds weaken and the period increases
from 15 to 18 seconds. Swimmers caught in a rip current should
swim parallel to the coast to escape the rip currents.
Marine...as of 10:41 am PDT Saturday...for today... a frontal
system will move through the area. Northwest winds will increase
in the southern waters this afternoon and over the northern waters
Sunday behind the front. Additionally... a long period west swell
continues to move through the region into early next week.
... Pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...sf Bay until 9 PM
Public forecast: rgass
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