UNDATED (KDAL) - The Minnesota DNR says despite some recent snow in much of the northern part of the state, snowmobile trails are not yet ready for riding. Although they officially open on December 1st, other conditions need to be met before trails open for use. They include adequate snow cover to allow for trail packing and grooming (usually about 12 inches) and frozen ground to allow for crossing of wet areas. Snowmobile travel is also not recommended on area lakes. The DNR says ice is forming but is not thick enough to support snowmobiles and can vary greatly from lake to lake and from different areas of the same lake. About 5 inches of clear ice is needed for snowmobile travel.