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Area forecast discussion 
National Weather Service Portland or 
300 PM PDT Friday Jul 18 2008 


Synopsis...a weak upper level trough over the northeast Pacific will 
slowly move east over the next few days. This will result in seasonal 
temperatures and dry weather...but with marine clouds affecting the 
coastal areas. 


&& 


Short term...visible satellite imagery shows marine stratus clouds 
dissipating from the south today...a little slower than yesterday. 
Clouds have dissipated in the Willamette Valley...except near the 
Columbia River and have dissipated over the central Oregon coast. 
Clouds over the southern Washington/northern Oregon coast and along 
the Columbia River will be slower to erode...probably late afternoon. 


Water vapor loops show an upper level low moving slowly east through 
southern b.C. With a trough extending over WA/Oregon...and another 
trough extending out to near 45n/136w. Models are stretching the 
upper level trough over the northeast Pacific further south off the 
central California coast...slowing its eastward progress. This will give less 
onshore flow and upper ridge development...giving US less warming 
than earlier thought over the weekend. 


An upper level low will develop off the California coast Monday and 
begin moving onshore Monday evening. Models are keeping this low far 
enough south that it will cause little effect over our area. The 
weather pattern will continue fairly similar to Sunday with morning 
clouds/afternoon clearing and temperatures a little above normal. 
Likens 


Long term...medium range models bring an upper level trough to the 
coast Tuesday...and move it through the forecast area Tuesday night. 
Another trough will approach the forecast area near the end of the 
week. The models are keeping the troughs dry over our area and will 
continue a dry forecast through the extended period. Onshore low 
level flow will continue with late night/early morning clouds through 
the week. 


&& 


Aviation...marine clouds are burning away as expected this 
afternoon...with the central coast and much of the interior either 
clear or beneath only scattered clouds. North coast will likely go 
bkn030-035 for a couple of hours around 00z...but will go back to 
overcast conditions quickly as marine layer re-solidifies this evening. 
Ceilings should be 2500 feet once they reform...and gradually drop to just 
below 2k feet. The same GOES for the central coast...though ceilings 
should hold off until closer to 05z. Inland...pretty much a repeat 
of last night. MVFR stratus will creep up the Columbia River and 
affect kttd and kpdx 08-10z...gradually spreading to khio and ksle 
by 12-14z. Stratus covered more of the Willamette Valley this 
morning than it has the last two...so expect that even keug might 
see some legitimate but brief MVFR ceilings tomorrow morning. Clouds 
will burn off on Sat similar to how they have done today. 


Pdx and approaches...sct-bkn VFR deck will completely burn away over 
the next couple of hours...with only clouds being north of terminal 
in Clark County. Tonight...expect a repeat of last night with MVFR 
ceilings making it to kpdx around 10z and lasting through about 20z Sat. 
Dalton 
&& 


Marine...no significant changes for the afternoon package. Winds 
are still fairly light early this afternoon. That being said some 
gusty winds are starting to show up along the coast and south of 
Lincoln City so forecast for Small Craft Advisory winds in southern waters still 
looks good. Buoy 46089 has managed to see peak gusts to almost 20 knots 
during the last several hours. Small Craft Advisory still looks OK 
for zone pzz270...though it may be starting an hour or two too 
early. At this point will let it ride though since it will be a 
marginal event. Should see small craft winds near shore Sat 
afternoon as well...mainly from Lincoln City to Florence. 
Otherwise...no rough bar for the next 24 hours and seas remain below 
10 feet for the foreseeable future. Dalton 
&& 


Pqr watches/warnings/advisories... 
or/WA...Small Craft Advisory for winds Cascade Head to Florence 
through early Sat morning. 
Small Craft Advisory for winds Cape Shoalwater to Cascade 
Head this afternoon and evening. 


&& 


Preliminary point probability of precipitation (probability of measurable precipitation) 
AST ----11 pdx ------ sle ------ eug ------ 


$$ 


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.