Hurricane Melissa maintained its powerful Category 4 strength on Sunday as it drifted slowly toward Jamaica, forecast to bring “catastrophic” flash flooding and landslides to the Caribbean nation.

Tropical Storm Melissa has strengthened into a hurricane and is expected to become a major hurricane by the end of the weekend, the U.S. National Hurricane Center said on Saturday.

“If those rains were to occur, you’re talking about catastrophic flooding potential,” said Jamie Rhome, the center’s deputy director.