MEXICO CITY (Reuters) -Storm Roslyn was weakening Sunday as it moved across west-central Mexico, though heavy rains and flash flooding continued, the U.S. National Hurricane Center (NHC) said. Roslyn hit land as a Category 3 hurricane at 5:20 a.m. local time (1120 GMT) near Santa Cruz in northern Nayarit, the NHC said, a Pacific coastal state home to popular tourist beaches like Sayulita and Punta Mita. By midday, however, Roslyn was downgraded to a tropical storm with maximum sustained winds that decreased to near 70 miles per hour (110 km per hour) with stronger gusts. More rapid weakening w…