Area forecast discussion 
National Weather Service San Francisco Bay area 
1029 PM PDT Sat Aug 29 2015 


Synopsis...a dry upper trough will remain anchored near the West 
Coast through next week. Temperatures near the coast will be near 
seasonal norms...while inland areas will generally be cooler than 
normal over the next seven days. No rain is expected. 


&& 


Discussion...as of 8:45 PM PDT Saturday...the southern end of a 
cold front dissipated as it moved into the San Francisco Bay area 
today. This front produced some light rain across the northern 
portion of our forecast area early today. Most locations picked up 
just a few hundredths. Sea Ranch on the Sonoma County coast 
received the most rainfall with 0.12". The airmass ahead of this 
front was warm and muggy...but much cooler and drier air has been 
spreading over our area behind the front today. High temperatures 
today were as much as 20 degrees cooler compared to yesterday. The 
biggest temperatures falls occurred on the San Francisco peninsula 
and in the East Bay valleys. 


Early evening temperatures and surface dewpoints are generally 
running several degrees below what they were at the same time 
last evening. Thus...we can expect more comfortable sleeping 
conditions tonight compared to the past couple of nights. 


Skies remain mostly clear this evening...although a few patches of 
low clouds have formed along the North Bay coastline. The low 
levels remain relatively well-mixed...and so coastal low clouds 
will probably remain rather patchy overnight. Most areas should 
remain mostly clear through the evening hours...allowing for a 
good look at the "super moon". 


After some patchy morning low clouds...Sunday is expected to be a 
mostly sunny and mild day with brisk onshore breezes. 


The models have been consistently holding the longwave trough 
position near the West Coast through next week. Temperatures near 
the coast probably won't vary much through the week...and will be 
close to seasonal norms. Inland temperatures are likely to climb slightly 
on Sunday and Monday as the airmass aloft warms a bit. Cooler 
conditions will then develop inland by midweek as the trough 
deepens along the coast and cooler air moves in from the 
northwest. Although the trough is forecast to deepen around 
midweek...the medium range models agree that moisture will be 
lacking and precipitation won't make it much farther south than the 
Oregon/California border. 


The upper trough is forecast to shift to the east late in the 
week...which should result in warmer weather by next weekend. 


&& 


Aviation...as of 10:20 PM PDT Saturday...drier air on west-northwest 
surface winds continues to move in over the entire area. Satellite 
shows some patchy stratus developing over Sonoma and Marin 
counties and over northern San Mateo County. Half Moon Bay reports 
broken MVFR ceiling. Otherwise it's VFR area-wide. Much drier air will 
also sweep in from the west tonight within a deeper layer of the 
atmosphere resulting in increased radiational cooling. Because of 
this expect additional stratus and fog patches tonight into Sunday 
morning. Clearing skies expected by middle-late morning Sunday. 


Vicinity of ksfo...only minor adjustments made to taf for slightly 
decreased amounts of MVFR ceiling forecast tonight. Will leave bkn012 
ceiling in from 11z-17z. VFR is very likely to return middle-late Sunday 
morning. West winds 20 gusts to 28 knots forecast 21z Sunday to 04z 
Monday. 


Ksfo bridge approach...similar to ksfo. 


Monterey Bay area terminals...drier air is moving in on west-northwest winds. 
It's mostly clear to clear around the area per satellite and 
observations. Localized IFR possible tonight...coverage should be 
at a minimum. VFR likely Sunday. 


&& 


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 9:53 PM PDT Saturday...northwest winds will 
increase over the coastal waters through the weekend. Gusty west 
winds are forecast Sunday afternoon and evening over the northern 
San Francisco Bay. A long period west swell will continue to move 
through the waters through the weekend and into early next week. 


&& 


Mtr watches/warnings/advisories... 
... Pinos to pt Piedras Blancas 0-10 nm 


&& 


$$ 


Public forecast: dykema 
aviation/marine: canepa 
beaches: drp 




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