MEXICO CITY, Oct. 22 (Xinhua) -- Mexico's Pacific coast on Monday braced for Hurricane Willa as the powerful storm advanced towards the mainland.

Willa was expected to hit the country's west-central coast Tuesday afternoon or evening, leading authorities to issue alerts and set up temporary shelters for flood victims.

The coordinator of the National Civil Protection agency, Luis Felipe Puente, told reporters at a press conference on Monday that an emergency was declared to ship potable water and food to communities in the western coastal states of Nayarit and Sinaloa, which were expected to bear the brunt of the damage.

Willa revved up into a Category 5 hurricane, the strongest, early Monday but lost steam as the day wore on and was downgraded to a Category 4 by 4 p.m local time (2100 GMT), according to the National Hurricane Center of the United States.

The storm was expected to make landfall in the southern Sinaloa town of Escuinapa as a Category 3 hurricane sometime late Tuesday, Roberto Ramirez, the head of the National Water Commission Conagua said.

However, that could still entail winds of up to 180 km per hour, enough to topple trees, lampposts and giant billboards, Ramirez added.

Officials were mainly concerned with storm surge, or rising sea levels, that could see 10-meter waves strike Mazatlan, a Sinaloa beach resort expected to receive heavy rains and flooding.

Vicente, another storm system, is forecast to hit west Mexico as a tropical depression almost at the same time as Willa.

In northern Nayarit, which borders on Sinaloa, officials urged coastal residents to begin evacuating as of Monday afternoon.

"We must not be overconfident," Nayarit Governor Antonio Echevarria told the press during a visit to the seaside town of Tecuala.

In its latest advisory, issued at 3 p.m. (2000 GMT), the U.S.-based National Hurricane Center said Willa was "expected to produce life-threatening storm surge, wind and rainfall over portions of west-central and southwestern Mexico." Enditem