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Area forecast discussion 
National Weather Service Seattle Washington 
230 PM PST Friday Nov 21 2008 


Synopsis...a Pacific storm will bring rain and mountain snow... 
along with blustery conditions...this afternoon and this evening. 
The weather will gradually improve tonight through Saturday morning 
as the storm moves to the east. Drier weather will return Saturday 
night and Sunday as high pressure aloft moves over the region. A 
weak weather system will arrive about Tuesday. 


&& 


Short term...front approaching coast and gales have been observed 
most waters. Rain will begin presently on the coast and spread 
inland this evening. Breezy to windy conditions expected most areas. 
Frontal passage over the Seattle metropolitan area between 03z and 
06z. At that point rain will change to showers...there will likely 
be a Puget Sound sound convergence zone...and showers will taper late. 


Saturday looks dry after a chance of morning showers that will 
mainly be in the mountains. Offshore flow then sets up Saturday 
night keeping things dry through Sunday. Went above MOS temperatures for 
the high Sunday as skies should be sunny and the offshore flow could 
bring warm east winds into many spots. 


Weak front hangs offshore Monday and that day is starting to look 
dry as well. Kept a chance of rain Monday in most zones. The front 
weakens and moves inland Monday night and Tuesday for continued 
chance of rain. Temperatures will be near climatic normals...50 or 
so...except for a warmer than average spell Sunday and possibly 
Monday. Chb 


Long term...weak front has main energy south of Washington on 
Tuesday but have kept chance probability of precipitation. Models diverge after that with 
GFS developing a dry offshore flow pattern the rest of the week and 
the Euro bringing another weak front inland about Thursday night. 
The solutions are not all that different otherwise. Have gone with 
the dry idea Wednesday through Friday. Burke 


&& 


Aviation...a strong upper level trough and cold front will move 
across West Washington this evening. West flow aloft will continue over the 
area Saturday...as a weak upper level trough moves east. Ceilings above 
bkn100 will plummet to MVFR 5sm rain bkn010-030 by 00z on the coast 
and around 02z Puget Sound sound...with frontal passage expected to occur 
2-3 hours after ceilings drop. Visible imagery shows lots of low-topped 
Post-frontal showers offshore that will reach the area through 
Saturday. Should be generally VFR with spotty MVFR around showers. 


Ksea...expect ceilings above bkn070 through about 02z then dropping 
rapidly to 5sm -ra bkn020-030. Frontal passage around 04z-05z. Strong S-SW 
winds aloft are still expected through 05z. 10,000-15,000 feet over 
kolm forecast 50-65kt...currently acars soundings have shown a maximum 
near 45 knots. 5000-8000 feet over ksea forecast 35-50kt...currently 
about 25 knots. Winds after 03z will turn more more SW-west instead of 
S-SW. Surface winds will remain S-southeast 5-15kt. Kam 


Marine...strong fast moving cold front over the offshore waters is 
still expected to reach the coast around 02z and Puget Sound sound 
04z-05z. Gales have been working out coast and Standard southeast affected 
areas. Also breezy over on north Hood Canal. No changes needed to the 
current warnings. Will keep the later expiration times to allow the 
midshift some cushion in-case conditions last a little longer past 
the evening forecast. The surface ridge building over the area 
Saturday looks good. No quarrels with the models. Kam 


&& 


Sew watches/warnings/advisories... 
Washington... 
pz...Gale Warning coastal waters...Strait of Juan Delaware fuca... 
Camano Island to Point Roberts...and Admiralty Inlet. 
.Small Craft Advisory Puget Sound sound and Hood Canal. 
.Small Craft Advisory Grays Harbor bar. 


$$ 


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