Tropical Storm Erin sputtered in the open waters of the eastern Atlantic when it was wrapped in a veil of dry, dusty air from the Sahara, which limited the storm’s ability to strengthen. But it’s still set to become a hurricane by the weekend,

The chances that the storm will make landfall in the U.S. have increased slightly after the path shifted south.

Tropical Storm Erin is expected to strengthen into a hurricane later this week in the Atlantic Ocean, according to the National Hurricane Center.