ROTTERDAM — A 19-year-old town man faces 16 misdemeanor counts of unlawfully dealing with a minor in connection with an underage drinking party at a local motel, police said. Blake E. Sowards, of 1315 Princetown Road, was charged Thursday in connection with the gathering on Sunday. Police said they also charged 16 youths with underage possession of alcohol, a violation. Police did not identify the motel. Sowards and the youths will appear in Rotterdam Town Court at a later date. Law enforcement officials said the advent of warmer weather creates an annual rush of underage drinking parties. Mechanicville police, for example, said they raided two house parties over the weekend that involved 23 people. Police said a 15-year-old girl hosted one party whole a 20-year-old man hosted the other.