I see no reason why a Soviet Invasion would not be a success beyond the planners wildest hope and dreams.
They have Arctic Brigade that train in Siberia without roads. They have Company sized units of snow plows with blades or blowers. The Soviets really embraced Hover craft on a huge scale that would make ports irrelevant.
Soviet equipment was built for the brutal Russian winter. Alaska would be easy.
http://www.darkroastedblend.com/2007...owmobiles.html
http://www.darkroastedblend.com/2007...owmobiles.html
http://www.darkroastedblend.com/2011...-to-north.html
http://www.cgsc.edu/carl/resources/csi/chew/chew.asp
http://militaryforces.ru/firearms-3-76.html
http://militaryforces.ru/firearms-3-75.html