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Nowcast

• 

• Now as of 9:41 am PST on January 27, 2012

  Areas of fog and freezing fog will continue through the morning before lifting this afternoon and warming above freezing. Visibilities will be below one quarter mile at times...especially near the Columbia River and in Clark and Cowlitz counties. Slow downand use caution while driving this morning.

Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Friday
• 
• High: 43 °
• Low: 31 °
• Partly Cloudy

• Saturday
• 
• High: 47 °
• Low: 38 °
• Partly Cloudy

• Sunday
• 
• High: 49 °
• Low: 38 °
• Rain

• Monday
• 
• High: 47 °
• Low: 38 °
• Rain

• Tuesday
• 
• High: 49 °
• Low: 38 °
• Rain

Area forecast discussion 
National Weather Service Portland or 
842 am PST Friday Jan 27 2012 


Synopsis...an upper level ridge will be over southwest Washington 
today and Saturday for dry stable conditions and areas of night and 
morning fog and freezing fog in light offshore low level flow. A 
Pacific front is expected approach the coast Saturday night and move 
through the forecast area Sunday and Sunday evening. This will be 
followed by a couple more systems every day or two next week. These 
fronts will be less strong than those of the last week or two. 
&& 


Short term...we got our areas of fog and freezing fog this morning 
with temperatures in many areas down into the 20s. An upper level ridge that 
was building along the coast will continue today and push onshore 
tonight and Saturday...maintaining the dry stable conditions. Light 
offshore flow today will be even less on Saturday. We expected some 
clearing to develop later today but with more fog and freezing fog 
expected tonight...clearing will be slower Saturday. 


The models show some higher clouds swinging through the area later 
tonight and Saturday out ahead of the next system...associated with 
the far southern edge of the warm front with the next system. This 
may impact the fog some tonight...but think things will cool off 
quickly enough this evening so that some fog and freezing fog will 
still form. Should again be a cold night tonight with at least some 
temperatures in the 20s. 


The next system is likely approaching the coast by later Saturday 
night. The GFS is the fastest model and the European model (ecmwf) the slowest...and 
have gone with a blend. Rain will spread onshore Sunday and have 
bumped probability of precipitation up with more categorical pop areas. The front moves 
through late in the day or in the evening...then showers behind the 
front will continue through Monday. This front is less intense than 
those of the last couple of weeks...but it still should be pretty wet 
and a bit breezy. Snow levels will come down to below pass elevations 
after the front passes through...and we might get close to needing an 
advisory in the Cascades for Sunday night and Monday. Tolleson 


Long term...no changes. Previous discussion follows... 
extended models are in much better agreement on the shortwave moving 
through the area to end the weekend. Placement of the trough should 
be offshore by Sunday evening...and will move through the forecast 
area Sunday night with increasing precipitation through Monday. 
Another small shortwave moves through late Tuesday into Wednesday. A 
new development in the extended models is to trend toward another 
ridge gradually building in over the area late next week. Have hinted 
at this possibility in the forecast...though confidence is not high. 
Expect a progressive weather pattern at least through middle week next 
week. Brown 
&& 


Aviation...surface high pressure centered off the north Oregon coast and 
also over the Washington and north Oregon Cascades resulting slight 
offshore low level flow. Extensive LIFR and IFR fog throughout the 
Willamette Valley as of 16z with most Airport sites below Landing 
minimums. Experimental GOES fog depth product indicates the fog layer 
to be 500 to 1000 feet deep. Local fog breakout program would suggest 
improvement to VFR will not occur until at least 21z...and likely a 
bit later at keug where the fog/stratus is a bit deeper. 
Elsewhere...VFR to dominate through at least 06z Sat. High clouds 
increase tonight so fog more likely to be hit and miss rather than 
widespread. 


Kpdx and approaches...LIFR at the terminal as of 16z...well below 
Landing minimum. Expect improvement to IFR around 18z...but local 
LIFR may last beyond 18z over western approaches. Fog/stratus should 
dissipate 20z to 21z. Weishaar. 
&& 


Marine...rather quiet on the marine front today. Will maintain the 
small craft for hazardous seas through tonight. Latest guidance 
suggest seas fall below 10 feet 12z Sat...but enp was running a foot or 
two high as of 12z this morning. May be able to end the small craft a 
bit sooner. The next system looks to bring south wind of 20 to 25 knots 
to the far northwest part of the waters as early as 00z sun...then spreading 
into all waters by 06z. Latest GFS boundary layer wind forecasts suggest 
possible 30 knots wind late Sat night...but the NAM is weaker. Will look 
at this closer for the afternoon forecast. Weishaar. 
&& 


Pqr watches/warnings/advisories... 
or...none. 
Washington...none. 
Pz...Small Craft Advisory for hazardous seas until midnight PST 
tonight for coastal waters from Cape Shoalwater Washington to 
Florence or out 60 nm. 


Small Craft Advisory for rough Columbia River bar until 10 PM 
PST tonight. 


&& 


&& 


$$ 


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.