MIAMI – Tropical Storm Priscilla was strengthening slowly in the Pacific Ocean off the coast of Mexico early Sunday.

The Miami-based National Hurricane Center said Priscilla was a “large tropical storm,” with tropical storm-force winds extending as far as 140 miles (220 kilometers) from its center.

Its maximum sustained winds were 65 mph (100 kph), the center said, and it was located about 305 miles (495 kilometers) south-southwest of Cabo Corientes and headed toward the northwest at 5 mph (7 kph).

A tropical storm watch was issued for part of the coast of southwestern Mexico, from Punta San Telmo to Punta Mita, with tropical storm conditions possible in the area Sunday and Monday. Rainfall of up to 6 inches (15 centimeters) was possible, and there was a danger of life-threatening surf and rip current conditions on the coast.

Priscilla was forecast to reach hurricane status by Sunday night or early Monday and generally move parallel to the coast in the coming days.

Another tropical storm off Mexico in the Pacific, Octave, was meandering far from shore with no landfall in the forecast and no coastal watches or warnings in effect due to the system.

Its maximum sustained winds strengthened slightly to 70 mph (110 kph).