752 
fxus66 kmtr 211720 
afdmtr 


Area forecast discussion 
National Weather Service San Francisco Bay area California 
1020 am PDT Thursday Aug 21 2008 


Discussion...as of 9:30 am PDT Thursday...short term weather 
concerns are minimal and no updates are planned this morning. 


The marine layer has largely been mixed out and disrupted by the 
trough passage and only patchy clouds remain around sf and mry bays. 
As mentioned by previous forecaster expect mostly sunny skies for 
this afternoon...even near the coast due to the poorly defined 
marine layer. Its noted the buoy/ocean temperatures are fairly mild with 
Monterey Bay buoy currently reporting 60 degrees...without the cold 
upwelling the marine inversion isn't as strong. However increasing 
northwest winds over the ocean and warming aloft will help to re-establish 
the marine inversion overnight into Friday morning near the coast and 
coastal valleys. Hard to really get a handle on any trends Friday 
into the weekend but the end of the work week should turn out 
seasonable with morning marine clouds into the coastal valleys 
followed by seasonable afternoon temperatures. 


The 850 mb temperatures are prognosticated to warm both Saturday and Sunday to as 
warm as 25-28 degrees celsius across most of the County Warning Area. Of course 
areas near the coast will see little overall change in temperature 
but inland valleys should warm into the lower 90s with MOS guidance 
for places like Concord and Livermore indicating highs in the upper 
80s...should be a nice end of Summer weekend. 


The long range shows some potential for interesting fire weather. A 
fall like trough moves into the Pacific northwest on Monday... 
dragging rain chances down to about Cape Mendocino. As is usually 
the case behind these first autumnal cool fronts strong surface 
high pressure builds over the Great Basin and a warm and dry thermal 
trough is realized over the Bay area. Of course model details waver 
slightly with each run but the European model (ecmwf) has been fairly consistent 
since Monday in indicating a favorable set up of the thermal trough 
near the coast from next Tuesday through Friday. This pattern 
would feature above normal temperatures...minimal marine influence...mild 
overnight lows...dry relative humidity readings and periods of dry offshore winds 
during the overnight and morning hours...especially Wednesday through 
Friday. This is still a long way out and will continue to monitor. 


&& 


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... 
... Pinos to Piedras Blancas 0 to 20 nm 


$$ 


Public forecast: r walbrun 
aviation/marine: Anderson 


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