Mayor James J. Fiorentini says the city is now enforcing its winter parking rules, which will remain in effect through April 1. During the months of December and February, overnight parking will be allowed on even-numbered side of the street; next month and from March 1 through April 15, it will be allowed on the odd-numbered side. In the event that a snow emergency is declared by the commissioner of public works, no parking is allowed on the following streets: Emerson; Essex; Main, from Merrimack Street to Monument Square; Merrimack; River, from County Bridge to View Street; Washington, from Washington Square to County Bridge; Water, from Main to Mill streets; White; and Winter. Violators are subject to a $25 fine and towing.