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Portland's rainy season begins right on cue

Portland's rainy season begins right on cue

by KGW Meteorologist Rod Hill

Bio | Email | Follow: @kgwrodhill

kgw.com

Posted on November 1, 2013 at 11:38 AM

Updated Saturday, Nov 2 at 11:55 AM

PORTLAND -- A strong cold front arriving Saturday morning will kick-off Portland's rainy season right on cue. 

Forecast models show the first two weeks of November will see at least some rainfall two out of three days. Current forecast outlooks call for near-normal and above rainfall for the months of November and December.  Here are the wettest monthly averages in order for Portland:

1.  November:  5.63 inches

2.  December:  5:49

3.  January:  4.88

4.  March:  3.68

5.  February:  3.66

The above numbers clearly show November and December to be the heart of the rainy season on a typical year.  While rainy days will be increasing, hours of sunshine will nearly disappear.  On average, November sees 24 days with total cloud cover and December sees 23 days with nearly zero sunshine.  Clear or mostly-sunny days over the next two months will on average total just 5 days.

As our weather becomes more active, keep in mind that the 7-day forecast will often see big changes past days three or four on a frequent basis.  The reason for the need to keep updated more often is the development of strong jet stream winds aloft.

(The above image shows jet stream winds, colored in blue, expected over Portland Saturday morning, Nov. 1.) 

Forecast | Radar | Cameras

As winter jet stream winds increase, computer modeling has a difficult task to keep up.  The good news is that strong storms are being better forecast than ever before. Strong storms driven by powerful jet stream winds will often show up 7 to 10 days out and be tracked very effectively until the storm front arrives.

Meteorologist Rod Hill, follow me @

www.facebook.com/kgwrodhill

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