MEXICO CITY -- Newly formed Hurricane Willa rapidly gained force and grew into an "extremely dangerous" Category 4 storm in the Pacific off Mexico on Sunday, with a potential to make landfall on a western stretch of coast between Mazatlan and Puerto Vallarta in the coming days.

The U.S. National Hurricane centre said the storm was "forecast to produce life-threatening storm surge, wind and rainfall over portions of southwestern and west-central Mexico beginning on Tuesday."

A hurricane warning was posted for a stretch of shore between San Blas and Mazatlan, while a tropical storm warning was in effect from Playa Perula to San Blas and Mazatlan to Bahia Tempehuaya. Hurricane force winds extended out 25 miles from the storm's core and tropical storm force winds were up to 90 miles out.

Willa was about 210 miles (340 kilometres) south-southwest of Cabo Corrientes late Sunday, with maximum sustained winds of 145 mph (230 kph). It was moving to the north-northwest at 7 mph (11 kph), but a turn toward the north was likely during the night or Monday.

The hurricane centre forecast 5 to 10 inches (12.5 to 25 centimetres) of rain across parts of western Jalisco, western Nayarit and southern Sinaloa states, with lesser amounts falling as it moves inland.

Meanwhile, a weakening Tropical Storm Vicente appeared to be a less potent threat farther south. Forecasters said it was expected to weaken into a tropical depression Monday night or early Tuesday while moving near Mexico's southern Pacific.

Its core was about 220 miles (355 kilometres) southeast of Acapulco with top sustained winds of 40 mph (65 kph). The hurricane centre said it could produce 3 to 6 inches (7.5 to 15 centimetres) of rain in parts of Guerrero, Michoacan, Colima and Jalisco states.