Officials in the northwestern Bahamas ordered the evacuation of low-lying areas and opened shelters in churches and schools on Saturday as they braced for a potential direct hit from the intensifying Hurricane Dorian.

The storm was upgraded to a Category 4 late Friday as it moved toward the United States. Packing winds of nearly 150 miles per hour on Saturday, it was expected to hit Grand Bahama Island and the Abaco Islands on Sunday and linger there into Monday.

The National Hurricane Center warned that because the storm’s movement had slowed, the area should prepare for “a prolonged period of life-threatening storm surge and devastating hurricane-force winds.” Rainfall of up to 15 inches was expected over the northwestern Bahamas, accumulating to as much as 25 inches in some areas. The storm was expected to cause surges of more than 15 feet, Bahamian officials warned.

Prime Minister Hubert Minnis appealed to residents living in the areas most at risk to leave their homes ahead of the storm, The Nassau Guardian reported.