If you intend to drive in the Tohoku area in winter - more precisely, anytime between from November to April - you should carefully check the following links.
Unlike other parts of Japan, and even Hokkaido, many roads are closed in Tohoku when there is snow around. Some popular onsen or ski areas can therefore be difficult to reach if you do not know exactly which roads are open. Keep in mind that some care navi
do not take in account those roads (but the more recent do)...
: map of Tohoku with links for each prefecture.
has a comprehensive list of closed road (winter, accident or work), but you need a Japanese yahoo account to have more details (without account : only list).
has a map with roads closed in winter around Hakkoda; there are really many roads closed there, so this site is a must if you intend to drive there.