Forecasters said on Friday that there was a 90 percent certainty that Hurricane Sandy would make landfall on the East Coast, but cautioned that it was too early to say where the giant storm would strike or how intense its winds would be when it hit.

Computer models show potential targets include an area stretching roughly from the Chesapeake Bay to southern New England.

The storm, now moving northwest at about 10 miles per hour, may stay off the coast in the Atlantic Ocean until Monday or Tuesday, but will likely combine with a colder weather system from the west to dump more than one foot of snow — perhaps as much as two feet — in the Appalachian Mountains of West Virginia, and cause strong winds all the way to the Ohio River Valley and eastern Great Lakes region.

The storm is also expected to dump as much as 10 inches of rain in the area where it makes landfall and to create a significant storm surge that will lead to flooding throughout a large coastal area, perhaps most seriously in Delaware, forecasters said.