A weaker La Nina in the southern Pacific and the current lack of a Greenland Block could signal a tough winter for the U.S. Northwest, AccuWeather.com said.

AccuWeather.com said La Nina is much weaker this year than last year. Last month, La Nina was rated at a magnitude 8.3 while in October 2010 it was 18.2 magnitude.

La Nina is a cooler-than-average tongue of sea surface temperatures in the southern Pacific Ocean that creates northward bulge in the storm track over the northern Pacific Ocean. The Greenland Block is a northward bulge in the storm track over Greenland that produces a southward dip in the storm track over the eastern United States,

"Without this block, the dip in the storm track would be in the western U.S. rather than the eastern U.S. The Northwest would be cold and stormy, the East warm and the Ohio Valley stormy," AccuWeather long range weather forecaster Paul Pastelok said Tuesday in a release.

Pastelock said the cold weather that has already arrived in Alaska and the storms that are kicking into gear in the Northwest are signs of a typical La Nina pattern, AccuWeather.com reported.