Tropical Storm Lala formed Thursday in the Pacific Ocean, and it could bring heavy rain and flooding to the Hawaiian Islands this weekend.

A hurricane watch was issued for the Big Island of Hawaii as Lala is forecast to bring rain to the region starting late Friday, the Miami-based National Hurricane Center said.

As of Thursday afternoon local time, Lala was located approximately 620 miles south-southeast of Hilo, Hawaii, moving northwest with maximum sustained winds of 50 mph, the hurricane center said. 

According to forecasters, Lala is expected to strengthen into a hurricane as it approaches the Big Island. The center warned that wind speeds on the windward sides of hills and mountains are often up to 30% stronger than near-surface winds.

The forecast track has the storm near or just south of the Big Island on Saturday, and it will pass south of the smaller islands during the rest of the weekend.

Lala could bring rainfall totals of 5 to 10 inches to the Hawaiian Islands, with up to 25 inches possible, forecasters said.

“This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain,” the National Weather Service said.

Hawaii Gov. Josh Green on Thursday signed a proclamation declaring a state of emergency ahead of Lala’s arrival, activating potential disaster relief funds and directing “all state agencies and officers to cooperate and extend their services, materials, and facilities as may be required to assist in emergency response efforts.”

The National Park Service also announced that most areas of Volcanoes National Park on the Big Island would close to visitors by Friday afternoon ahead of the storm’s arrival. 

Elsewhere in the Pacific, Tropical Storm Hernan formed on Thursday about 1,460 miles west of the southern tip of Baja California. The storm is not expected to threaten land.