Area forecast discussion 
National Weather Service San Francisco Bay area 
255 PM PDT Thursday Aug 21 2014 


Synopsis...night and morning low clouds and slightly below 
normal afternoon high temperatures will continue through the 
weekend. Warmer temperatures are possible inland by the middle of 
next week. 


&& 


Discussion...as of 02:45 PM PDT Thursday...clouds have cleared 
back to the coast this afternoon. Unlike yesterday the southerly 
flow has weakened allowing even the North Bay to clear out by late 
morning...so that after a cool start in the 50s Santa Rosa is now up 
to 80. 


The marine layer will stay steady around 2000 feet tonight 
maintaining a similar stratus pattern...while a trough builds into 
the Pacific northwest slightly cooling temperatures tomorrow. As 
the trough digs southeast into the Great Basin Friday night into 
Saturday the marine layer looks to deepen leading to drizzle along 
the coast and temperatures stay slightly below normal into the 
weekend. 


Early next week the trough shifts east as a ridge builds just 
offshore. The GFS and European model (ecmwf) agree that the trough will quickly 
expand and progress eastward by Tuesday leading to a warming 
trend. The Gem is a bit slower holding off the warming until 
Wednesday. 


&& 


Aviation...as of 10:30 am PDT Thursday...as forecast, clearing 
happened earlier today although still seeing MVFR to IFR ceilings 
across Napa/Sonoma which should burn off shortly. Looking for VFR 
for the afternoon into the early evening hours for all terminals. 
Sea breeze winds also expected to ramp up 20z-02z. Models in good 
agreement for a late return for MVFR ceilings for most areas tonight. 
Moderate to high confidence. 


Vicinity of ksfo...VFR through the day with winds 280-300 gusting 
up to around 20 knots from 21z to 02z. Late return of stratus 
expected tonight -- possibly after 11z. High confidence through 
02z. Moderate to high confidence on the return for tonight. 


Ksfo bridge approach...similar to ksfo. 


Monterey Bay area terminals...VFR through the day with winds 
240-280 up to 12 knots. Return of MVFR ceilings after 02z although 
possible they could be later than that time. High confidence 
through 0z. Moderate confidence after that. 
&& 


Marine...as of 2:23 am PDT Thursday...generally tranquil conditions 
will continue through the evening. By Saturday the surface 
pressure gradient is expected to increase ... in 
strengthening winds. A moderate period southerly swell generated 
by tropical storms will move into the region later this week. 


&& 


Mtr watches/warnings/advisories... 
... Arena to pt Reyes 10-60 nm from 11 PM 
Small Craft Advisory...sf Bay north of the Bay Bridge until 11 PM 


&& 


$$ 


Public forecast: ac 
aviation/marine: Bell 


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