Area forecast discussion 
National Weather Service San Francisco Bay area 
251 PM PDT Friday may 24 2013 


Discussion...as of 2:47 PM PDT Friday...cool weather ahead with a 
chance for much needed rain early next week. 


Afternoon visible satellite and metar observations indicate mostly 
clear skies across the region. A few lingering low clouds remain 
along the San Mateo coast and around Monterey peninsula...but 
otherwise pretty nice afternoon. 24 hour trends also reveal that 
many locations are running a few degrees warmer than 
yesterday...especially interior locations. 


Synoptically speaking...a nearly stationary upper level trough off the 
Pacific northwest coast continues to be the dominant weather feature for much 
of the West Coast. 


Short term(tonight-monday)... 
the aforementioned trough will remain through the short term as a 
series of upper lows swing through the trough. As a 
result...unseasonably cool weather will continue through much of 
the short term. In addition...model guidance has been rather 
persistent with bringing a strong upper low through the trough and 
toward the California coast on Monday resulting in rain chances. Model 
guidance has had a difficult time with the exact timing of precipitation 
on Monday...but consensus develops rain over the North Bay early 
Monday and then gradually spreading rain southward through early 
Tuesday. Rainfall amounts appear to be rather light...up to a 
quarter of an inch for the North Bay and a few hundredths to a tenth a 
an inch southward. None the less...persons with outdoor activities 
on Memorial Day may want to thinking about packing rain gear for 
some afternoon showers. 


The persistent onshore flow and cool air aloft will also produce 
unable-Summer like temperatures. Many locations over the weekend will 
be a few degrees below normal and by Monday some locations will be 
as much as 10 below normal. Highs for the up coming weekend will 
generally be in the 60s along the coast and 70s to near 80 inland. 
Monday will be the coolest day of the short term with many 
locations struggling to break 70 degrees. 


Long term(tuesday-friday)... 
a few lingering showers will be possible Tuesday as the upper low 
exits the region. The rest of the long term will feature a gradual 
warming and drying trend with more seasonable temperatures. 




&& 


Aviation...as of 10:30 am PDT Friday...VFR conditions will 
prevail through many of the terminals through at least the evening 
hours. Moderate confidence. Onshore flow will increase early this 
afternoon and continue through the evening hours. Latest short 
term model guidance suggests patchy stratus at many of the 
terminals late tonight. However...the short term guidance has been 
performing poorly in the last few days...so stratus was only added 
to the Monterey Bay. Low confidence. 


Vicinity of ksfo...VFR conditions through the forecast. Moderate 
to high confidence. Moderate west winds this afternoon...with 
gusts peaking around 30 knots between 21z today and 03z Saturday. 


Ksfo bridge approach...similar to ksfo. 


Monterey Bay area terminals... VFR conditions through at least 
06z. Low confidence. Moderate onshore winds this afternoon with a 
return to stratus and possible IFR ceilings as early as midnight. 


&& 


Mtr watches/warnings/advisories... 
... Pt to pt pinos 0-10 nm until 3 am 
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 pinos to pt Piedras Blancas 0-10 nm 
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm 
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm 
Small Craft Advisory...sf Bay until 9 PM 
Small Craft Advisory...mry Bay until 9 PM 


&& 


$$ 


Public forecast: mm 
aviation/marine: Riley 


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