Weather

176 
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Area forecast discussion 
National Weather Service Portland or 
300 am PDT Tuesday Oct 7 2008 


Synopsis...a strong Pacific cold front was moving through the 
forecast area early this morning and will be east of the Cascades 
later this morning. Westerly flow aloft behind this system will 
dominate through middle week with a little bit of precipitation at times 
mainly over the northern mountains and coast. A cool system will 
dig south out of the Gulf of Alaska and bring some more rain and 
showers to southwest Washington and northwest Oregon Thursday and 
Thursday night with lowering snow levels in the Cascades...lowest 
of the fall season so far. An upper level ridge will move in this 
weekend and early next week for dry and warmer weather again. 
&& 


Short term...coastal observations show the incoming cold front has 
moved onshore early this morning with decreasing wind along the 
coast. National Weather Service Doppler radar shows the heaviest 
and steadiest echoes have moved into the Cascades early this morning. 
The front will move east of the Cascades later this morning. 
Precipitation behind the front will turn showery and decrease from 
the south as a surface high builds in. The models do indicate 
westerly flow aloft with weak vorticity lobes will swing through 
for the next couple of days...with the best chance of any showers 
after this morning to be over the northern mountains and the northern 
coast zones. Snow levels will drop today and Wednesday but generally 
stay just above the passes. Will need to watch for some patchy fog 
with the wet ground and longer nights. 


The next system digs south out of the Gulf of Alaska Wednesday night 
and Thursday. It appears the associated front approaches the north 
coast late Wednesday night and sweeps through the area Thursday 
morning. This will be followed by more showers. The snow level drops 
well below the Cascade passes Thursday and Thursday night...lowest of 
the fall so far. Precipitation amounts look a bit weak for a Snow 
Advisory but might get close at higher elevations. Winds will be 
a bit breezy from the northwest Thursday especially at the coast and 
over the mountains. Have upped probability of precipitation and lowered snow levels for 
the Thursday system. Tolleson 


Long term...minor changes. Previous discussion follows... 
improving weather conditions expected for the extended period. As the 
cold upper level trough swings to the east...a possible strong ridge 
builds in over the forecast area into the weekend. The intensity of 
the departing trough and incoming ridge are not agreed upon by the 
Middle Range models so therefore have gone with a more middle of the 
Road solution. Should expect to see a drying trend by early weekend. 
Brown 
&& 


Aviation...conditions predominantly VFR this morning except in wake 
of front where a thin line of MVFR exists. Post frontal air mass 
expected to transition from high end MVFR to low end VFR ceilings this 
morning. 


Kpdx and approaches...MVFR ceilings will lift to VFR by 12z. Showers 
will fill in behind front with the possibility for some MVFR ceilings. 
Chance for MVFR ceilings lowers below 40 percent by 19z. Wolfe 
&& 


Marine...winds falling below small craft criteria by midday as high 
pressure builds over the waters today. Front built seas to 21 feet at 
buoy 46005...this translates to 16 feet seas arriving in the waters by 
01z. Seas will remain above 10 feet through Wednesday morning. Wolfe 
&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for rough Columbia River bar 
through Wednesday morning. 
Small Craft Advisory for winds Cape Shoalwater to Cascade 
Head through late this morning 
Small Craft Advisory for winds Cape Shoalwater to 
Florence through early this morning. 
Small Craft Advisory for hazardous seas Cape Shoalwater 
to Florence through Wednesday morning. 


&& 


$$ 


More weather information online at... 
http://weather.Gov/Portland 


This discussion is for northwest Oregon and southwest Washington from 
the Cascade crest to 60 nautical miles offshore. The area is commonly 
referred to as the forecast area.