Officials in the northern Caribbean warned Thursday of heavy rains and dangerous swells as Tropical Storm Erin approached the region.

The hurricane center explicitly calls for Erin to rapidly intensify before the weekend — a term used when a storm’s sustained winds get at least 35 mph stronger in 24 hours. In this case, forecasters expect Erin to leap from a Tropical Storm on Friday to a major Category 3 hurricane by Sunday.

Tropical Storm Erin is forecast to rapidly strengthen into a hurricane this weekend as it nears the northeastern Caribbean and Bahamas, raising concerns for strong winds, heavy rain, and dangerous surf along the islands.