Weather

906 
fxus66 kmtr 212200 
afdmtr 


Area forecast discussion 
National Weather Service San Francisco Bay area California 
300 PM PDT Thursday Aug 21 2008 


Discussion...as of 3:00 PM PDT Thursday...short term weather 
concerns remain minimal Friday through the weekend. 


The main storm track remains well to our north but is unusually 
active for late August. The last trough was strong enough to 
temporarily disrupt the local marine inversion. However warming 
aloft and increasing northwest winds over the waters will enhance the 
local upwelling and the marine inversion will become more clearly 
defined overnight along the coast and around the bays with a depth 
between 1000-2000 feet. Expect low clouds into sf Bay again tonight 
and of course around mry Bay and the Salinas valley by sunrise 
Friday. Temperature trend for Friday afternoon should feature 
slightly warmer temperatures inland as 850 mb temperatures warming slightly. 
In general temperatures tomorrow through the weekend will be near 
seasonable levels...however the inland trend should be slightly 
warmer each day with more readings into the lower 90s for inland 
valleys by Sunday afternoon. 


On Monday an unseasonably strong cool front/upper trough will move 
into the Pacific northwest with increased onshore flow around the 
Bay area which may allow temperatures to drop a few degrees on Monday with 
increased stratus coverage and a slower burn-off. 


The European model (ecmwf) continues to be Adamant in advertising a fairly significant 
warming and drying trend (rh values) from Tuesday through Friday of 
next week. Upper heights are not too impressive but 1000-500 mb 
thickness values in the 585 dm range with the thermal trough along 
the coast will minimize any coastal cooling effects. In general 
chamber of Commerce weather appears to be in store behind mondays 
front but fire weather concerns will need to be monitored as we head 
towards next week. This would be a little early for strong autumnal 
offshore wind events but as we approach the end of August with an 
early fall in the northern rockies anything is possible. 


&& 


Aviation...as of 10:20 am PDT Thursday...latest satellite pictures 
show clearing taking place over the sfo peninsula. Also marine layer 
depth is much shallower than yesterday with an inversion depth of 
around 1000 feet. Sfo approach zone is expected to clear by 18z. 
Westerly winds at sfo are expected to ramp up this afternoon with 
sustained winds of 18 knots with gusts to 28 knots after 21z. 


&& 


Mtr watches/warnings/advisories... 
... Waters except Pigeon pt to pt pinos 0-20 nm 
and mry Bay. 


$$ 


Public forecast: r walbrun 
aviation/marine: Anderson 


National Weather Service on the web at weather.Gov/sanfrancisco