Weather

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afdsew 


Area forecast discussion 
National Weather Service Seattle Washington 
850 am PDT Friday Oct 10 2008 


Synopsis...strong high press aloft offshore is expected to slowly 
drift east into the Pacific northwest through the weekend. This 
weather pattern will provide generally clear skies..crisp mornings.. 
and areas of night and morning fog and low clouds. The high pressure 
aloft is forecast to move east of the Cascades Monday as a weak warm 
front approaches for a threat of rain. Westerly flow aloft will 
prevail next week bringing a few weak Pacific fronts through the 
region. 


&& 


Short term...gosh..it feels like fall already. The high amplitude 
upper ridge is now inching inside 140w while our pesky upper low has 
now sagged southeast into the Great Basin. Cool northerly flow aloft and at 
the surface has developed over our area. 


Morning satellite images and surface observations show areas of low 
clouds and some fog from mainly Arlington and Everett southward through 
Puget Sound sound and down to the Columbia River. Upslope flow on the 
Olympics also producing some clouds near Port Angeles and Sequim. 
The rest of the area is generally clear and cool this morning and 
the morning clouds and fog should dissipate by midday for lots of 
sunshine but high temperatures remaining below seasonal norms. 


Then there is tonight. With the clearing skies..cool air mass and 
easing northerly winds..look for our first more widespread night of 
near or below freezing temperatures. The exceptions will be areas near 
bodies of water like Puget Sound sound..the Strait and coastal waters. 
Look for a statement to be issued on this later situation today. Can 
you say frost on the pumpkin? 


The upper ridge will dominate the weather through Sunday as it 
slides east over the Pacific northwest. So clear skies with the 
exception of some night and morning fog or low clouds. Temperatures will 
moderate a bit each day..climbing close to average by Sunday. 


By late sun..fresh forecast guidance this morning continues the 
trend of easing the upper ridge inland as a weak Pacific warm front 
approaches the coast. Anticipate an increase in cloud cover along 
the coast and olympic peninsula followed by a threat of rainfall Sun 
night. Fall is here. Buehner 


Long term...from previous discussion..westerly flow aloft will 
follow the upper ridge and prevail across the forecast area Monday 
through Thursday. Best guess is that two weak frontal systems 
embedded in the zonal flow will move through western Washington 
during that four day period...but longer range models continue to 
show poor agreement and consistency on the timing. The current 
timing in the extended forecast does not agree too well with the 
most recent GFS...but given the uncertainty it is fine for now. 
Mcdonnal 


&& 


Aviation...an offshore upper level ridge of high pressure producing 
mostly dry northerly flow across western Washington today. Exception 
this morning is moisture near the surface resulting in areas of low 
clouds and fog especially near the typical water sources. Fall 
Morning Sun weaker in intensity...so burnoff time will take a little 
longer probably near 18-20z for a mostly sunny fall afternoon. Next 
problem is tomorrow...Saturday..morning. With widespread freezing or 
near freezing early morning temperatures...frost out of moisture 
likely so morning fog formation could be delayed to later in 
the morning or not at all. Will look closer at this issue for 
afternoon package. Winds to remain northerly today...decreasing 
over the weekend as the ridge moves further inland over western 
Washington. Prange 


Ksea...MVFR low clouds will persist through 18-20z...and 
northerly winds 5 to 10 knots. Skies will clear out this afternoon. Patchy 
fog is expected Sat morning. Prange 


&& 


Marine...a strong 1034 mb ridge of high pressure centered offshore 
along 135w will continue to produce northerly flow across West Washington 
today. Seas this morning at buoy 041 were around 10 feet but should 
see swells begin to subside late this afternoon. Northerly wind 
component today and through the weekend. Wind speeds should begin to 
diminish as pressure gradients relax later today and into the 
weekend. Onshore flow will increase early next week. Prange 


&& 


Sew watches/warnings/advisories... 
Small Craft Advisory coast and Grays Harbor bar. 


$$ 


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