Beach goers watch waves generated by Hurricane Sandy along a breezy Coligny Beach Park on Hilton Head Island, S.C., Saturday morning, Oct. 27, 2012.

High water from Hurricane Sandy surrounds a car along Hampton Boulevard in Norfolk, Va., near Larchmont Crescent, Oct. 28, 2012.

Jessica Ospina, left, and Allison Kane of Virginia Beach, Va., lean into the strong wind and rain off the Chesapeake Bay near the Chesapeake Bay Bridge tunnel in Virginia Beach, as Hurricane Sandy works its way north, battering the U.S. East Coast, Oct. 28, 2012.

NEW YORK -- Hurricane Sandy is gaining strength and has taken a left turn toward the East Coast and its date with two other weather systems. An official with the National Oceanic and Atmospheric Administration is calling it "the worst-case scenario."

The storm, with tropical storm-force winds extending almost 500 miles from its center, is expected to blow ashore along the New Jersey coast tonight or early tomorrow. Combined with high tides and a full moon, it brings the fear of a huge surge of seawater.

The combined storm is expected to affect everyone from the East Coast to the Great Lakes, with up to 3 feet of snow forecast for the West Virginia mountains.

Airlines have canceled thousands of flights in the Northeast and air travel could come to a halt for at least two days. That has caused a ripple effect across the globe.