Hurricane Norbert strengthens

(CNN) - Hurricane Norbert - an "extremely dangerous" Category 4 hurricane - began its expected turn toward the Baja peninsula late Wednesday, forecasters said.

Forecasters expect Norbert to make landfall along the southern end of Baja on Saturday, though hurricane forecasts are unpredictable and can change considerably.

At 11 p.m. ET Wednesday, Norbert was about 420 miles (675 km) south-southwest of the southern tip of Baja California, the National Hurricane Center in Miami, Florida, said. The storm's maximum sustained wind speeds held steady at near 135 miles an hour (215 km/hr).

Forecasters expect Norbert to begin to weaken Thursday. They predict that it will be a Category 2 storm at landfall.