Six-foot drifts driven by 50-mile winds piled up in Manhattan today and the worst snow-storm to hit the Northeast in nine years virtually closed down Boston and played havoc along the entire Eastern Seaboard.

The storm's icy tentacles reached as far west as Kentucky and Ohio, blanketing Cincinnati under a record 16 inches of snow within 24 hours. It was the East's third snowstorm in eight days.

New York Mayor Edward Koch declared his first snow emergency. The city's airports were closed as crews labored to clear the runways of dangerous drifts.

Amtrak's Metroliner service had to be shut down lest the air intakes on the fast trains' undercarriages become clogged with snow.

Thanks to 225 plows, the New Jersey Turnpike was open - under a 35 mph speed limit - for anyone, as a turnpike official put it, "stupid enough to drive."

Unlike the storm of 1969, this one did not catch large numbers of people on the roads or at the airports.

If this city was coping reasonably well with 2,500 workers and 1,100 vehicles on storm duty, up north in Buffalo a note of amusement was heard.

The city that became synonymous with snowdrifts and subzero weather last winter, when it was under a seemingly perpetual blizzard, has been having a mild winter.

"We are sypmathetic with the rest of the nation, but it's nice to have company. We're glad we're no longer the only place people turn to for reports of bad weather," said Charles Poth, assistant to Buffalo's mayor.

On the other hand, in Oswego, N.Y., on Lake Ontario, Mayor John Fitzgibbons said 22 inches of snow was expected today and tonight on top of the 52 inches that have fallen since Saturday.

"We're desperately trying to keep your sense of humor," Fitzgibbons said. Oswego's 23,000 residents are taking it pretty much in stride, he added. "We've only lost three school days and about the same number of business days."

Massachusetts Gov. Michael Dukakis ordered all state offices closed at 10 a.m. and went home himself at 12:30 p.m. after going on television to promise "we are going to do everything we can to aid the cities of Massachusetts."

"We have a dangerous situation. No travel should be attempted unless it's an emergency," the Weather Service warned in Boston.

The warning might have applied not only to motorists but to Boston public transportation users. At an outdoor station, a subway train apparently skidded along slippery rails in the blizzard and slammed a standing train, injuring at least 16 persons.

The accident - Boston's second rapid transit collision in three days - halted surface trains and stranded hundreds of passengers. The transit authority sheltered them in a repair shop and sent our for groceries.

Amtrak, besides its Metroliner troubles, was plagued with problems on conventional trains.

A derailment between Baltimore and Washington halted all traffic. Passengers piled up in the Baltimore station until buses were organized to drive them to the Capital.

Train service north from New York was interfered with by a power failure for a short time during the morning, but trains were running - with long delays.

The Long Island Rail Road, which carries 100,000 New York commuters a day, canceled all trains this morning, but in midafternoon it resumed limited service on most routes.

In the somewhat curious tradition of New York mayors, Koch embarked on a tour this afternoon to inspect snow removal operations. During the 1969 storm, a walking tour by Mayor John Lindsay generated a blizzard of criticism for not moving more quickly to clear the streets. Koch's trip to Queens and Brooklyn was reported free of unpleasant incidents.

Gov. Hugh Carey authorized banks to close. The New York and American stock exchanges didn't open until noon. Trading was light and they closed early.

A potentially hazardous situation arose during the night when an inch-thick sheet of ice formed on the sheer tower wall of the new citircorp. Center. Police ordered a block of 54th street closed until the ice melted.