Tropical Storm Madeline forming in the Pacific Ocean off the western coast of Mexico.
CNN  — 

Tropical Storm Madeline formed in the Pacific Ocean off the western coast of Mexico Saturday afternoon.

Carrying maximum winds sustained at 45 mph, the storm was about 280 miles south-southwest of Manzanillo, Colima, and 520 miles south-southeast of Cabo San Lucas, on the tip of Baja California.

The outer bands of the storm are expected to interact with the remnants of Tropical Storm Lester and produce torrential downpours. More than 10 inches of rain are possible in Guerrero, Michoacán and Oaxaca.

In areas of southern Nayarit and Jalisco – including Puerto Vallarta – residents could see heavy rains, gusty winds and waves up to 13 feet high along the coasts.

Rainfall from both Lester and Madeline could lead to landslides, bring up water levels in rivers and streams, and flood low-lying areas.

Residents are “urged to heed the SMN (Servicio Meteorológico Nacional) warnings and follow the guidance of state authorities,” Mexico’s National Water Commission said. Ships were urged to take extreme precautions due to high winds and waves off the coast.

Lester has already dissipated over Mexico, but its heavy rains are expected to continue for parts of coastal southern Mexico into Sunday, according to the National Hurricane Center.

Meanwhile, a hurricane warning was issued for Puerto Rico as Tropical Storm Fiona approached Saturday, with “Life-Threatening Flooding and Mudslides” possible over the next several days, authorities said.

Hurricane conditions were expected across parts of Puerto Rico Sunday and possibly in the US Virgin Islands Saturday night, according to the Hurricane Center.

CNN’s Nouran Salahieh contributed to this report.