Texas Braces for Hurricane Harvey

Forecasters says Hurricane Harvey, a strong Category 2 storm, could strengthen into a Category 3 hurricane when it hits southeast Texas late Friday or early Saturday. Rain is expected to range from 10 to 20 inches, and some areas could receive as much as 30 inches.

"This is going to be a storm we talk about, unfortunately, for at least the next seven days," said ABC News chief meteorologist Ginger Zee.

Harvey is expected to be the largest storm to hit the United States in 12 years and the largest storm to hit Texas in two decades. Corpus Christi and Houston are two major cities in the projected path of the storm. 

The National Weather Service cautions Harvey could bring a potentially devastating storm surge, heavy rainfall and winds of more than 100 mph to segments of the Lone Star State.

Residents have been urged to evacuate, and the mass exodus has caused extensive traffic jams along the state's highways.

"Texas is about to have a very significant disaster," said Brock Long, director of the Federal Emergency Management Agency.

A European storm model suggests a worst-case scenario. In this prediction, Harvey strikes land, then returns to the Gulf of Mexico and storms the shore once again a few days later. 

Governor Greg Abbott requested 700 National Guard members, and the Ports of Corpus Christi and Galveston are closed.