Hurricane Willa has weakened slightly off Mexico's Pacific Coast and is now a Category 4 storm, but remains "extremely dangerous" ahead of an expected landfall Tuesday.

The U.S. National Hurricane Center says Willa's maximum sustained winds are now 155 mph (250 kph). That's just 1 mph below the threshold for a Category 5 hurricane.

Regardless of category, the storm is expected to bring life-threatening storm surge and rain over parts of west-central and southwestern Mexico.

A hurricane warning is in place for a stretch of coastline from San Blas to the popular resort city of Mazatlan, as well as the offshore Islas Marias, a set of islands that include a nature preserve and a federal prison.

Nearly three years ago to the day, Hurricane Patricia, one of the most powerful storms on record, struck Mexico's Pacific coast with winds that tore down trees, moved cars and forced thousands of people to flee homes.

Meanwhile, Tropical Storm Vicente, with maximum sustained winds of 45 miles per hour (72 kph), was churning some 365 miles (590 km) southeast of Manzanillo. The storm is expected to approach the southwestern coast of Mexico on Tuesday.

While Vicente is expected to weaken to a tropical depression by Monday night or Tuesday, it could produce major rainfall and the risk of flash floods and landslides, the NHC said.

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