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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 45 °
• Low: 36 °
• Rain

• Tuesday
• 
• High: 45 °
• Low: 36 °
• Chance of Rain

• Wednesday
• 
• High: 47 °
• Low: 38 °
• Chance of Rain

• Thursday
• 
• High: 49 °
• Low: 40 °
• Rain

• Friday
• 
• High: 49 °
• Low: 40 °
• Rain

Area forecast discussion 
National Weather Service Portland or 
843 PM PST sun Feb 12 2012 


Synopsis...a stretching and elongating frontal system has spread 
into southwest Washington and northwest Oregon this evening...with 
the bulk of the energy of this system headed toward northern 
California. Snow levels will be well below the Cascade passes with 
this system. The main low associated with this system will move 
south of our area Monday morning with showers decreasing the 
remainder of the day and into Monday evening. The next system will 
come in from the northwest on Tuesday with more rain. Snow levels in 
the mountains will be on the low side again. A brief break is 
possible on Wednesday before another system moves through on 
Thursday. Another system is likely this weekend. 
&& 


Short term...National Weather Service Doppler radar has shown echoes 
spread in across southwest Washington and northwest Oregon this 
evening as an elongating north south oriented frontal system has 
moved onshore. The main energy with this system is headed toward 
northern California...and this will limit the rainfall amounts in our 
area. But everywhere in our area will get wet. 


Snow levels are rather low with this system...and will be in the 2000 
or 2500 foot range...possibly affecting the higher Cascade foothills 
and the higher Coast Range as well. 


The associated surface low is off the coast and will sag south 
overnight. The whole low will likely be south of our area during 
Monday morning...and we should see decreasing showers the remainder 
of Monday and into Monday evening. We may see some patchy fog late 
Monday night or early Tuesday...but that will partly be dependent 
whether we get some breaks in the lower clouds. 


The next system is expected to move in from the northwest Tuesday. 
Snow levels will again be on the lower side...perhaps a little lower 
than those Monday. The European model (ecmwf) has been the most consistent model... 
with the GFS the least consistent model. Probability of precipitation have been bumped up to 
likely but no higher yet until a bit more model consistency is 
achieved. This system moves south by Wednesday and we have a decent 
chance at a break on Wednesday before the next system Thursday. 
Tolleson 


Long term...no changes. Previous discussion follows...plenty of 
uncertainty remains in the extended forecast...as progressive split flow 
is expected to continue. However...the models are beginning to 
converge on a solution that brings another brief shot of rain on Thursday 
as a frontal system drives through the top of the ridge through 
BC/Washington. Going into the weekend...models again diverge. The one 
thing they can agree on is that we will continue to remain in a 
progressive winter time pattern...with the potential for a couple of 
systems to impact the Pacific northwest. Kept probability of precipitation above climatology through the 
weekend. Jfp 
&& 


Aviation....as rain associated with the front continues 
overnight...expect to see MVFR conditions become more widespread. 
Expect to see a mix of low end VFR to MVFR ceilings continue Monday behind 
the front as precipitation turns more showery after 17z. 


Kpdx and approaches...VFR conditions expected to give way to 
predominantly MVFR conditions overnight...mainly the result of 
lowering ceilings. A light rain and drizzle expected to continue 
overnight...turning to showers Monday morning. Areas of MVFR ceilings appear 
likely to remain well into the day Monday...but with VFR becoming more 
predominant by afternoon...after 19z. 
&& 


Marine...expect to see winds picking up overnight as a weak front 
moves inland...and northwest winds pick up behind the front. Gale force wind 
gusts still look possible late tonight into Monday morning over the 
southern outer waters...while the rest of the area sees winds peaking 
in small craft category. Following behind the front...seas will also 
pick up tonight and Monday as a westerly swell train arrives...with wave 
heights expected to reach 10 feet late tonight... and to the middle teens 
late Monday. 
&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for winds for tonight through Monday 
afternoon from Cape Shoalwater to Cascade Head from 10 to 
60 nm offshore...and Cascade Head to Florence from 0 to 
10 nm offshore. 
Gale Warning for tonight through 10 am Monday morning from 
Cascade Head to Florence from 10 to 60 nm offshore. 
Small Craft Advisory for hazardous seas for tonight 
through Tuesday from Cape Shoalwater to Cascade Head from 
0 to 60 nm offshore...and Cascade Head to Florence from 
0 to 10 nm offshore. 
Small Craft Advisory for rough Columbia bar conditions 
for this evening...and for Monday through Tuesday. 


&& 


$$ 


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.