* Snow could knock out electrical power
* Travel delays also possible (Updates with snow starting in Northeast, other details)
By Neale Gulley
BUFFALO, N.Y., April 22 (Reuters) - Winter made a comeback on Sunday as a powerful storm brought rare, late season snow to the northeastern United States, and parts of New England faced the threat of flooding.
After a milder-than-normal winter in most of the country, snow fell late Sunday from the mountains of West Virginia to the southern shores of Lake Erie in Pennsylvania and New York, with as much as one to two feet (.3 to .6 meters) expected over the next 36 hours.
In Buffalo, New York, 3 to 6 inches (8 cm to 15 cm) of snow were expected over the period, said Bob Hamilton, meteorologist with the National Weather Service in Buffalo.
He said there could be power outages from the wet, heavy snow on power lines.
"It's going to cause some damage, no question about that," Hamilton said.
Rain drenched the Boston area on Sunday, prompting the Boston Red Sox baseball team to postpone an evening game against the New York Yankees.
The National Weather Service warned of flooding across southern New England as heavy rain was expected to continue falling through the night. It issued a flood watch for parts of northern Connecticut, Massachusetts, southern New Hampshire and Rhode Island, according to its website.
Late season storms are unusual, but not unheard of, in the Northeast, Hamilton said.
"It happens every 15 years or so. It's something you deal with when you live in this part of the country," he said.
The rain extended south to Washington, D.C., and into North Carolina, spurred by a deep low pressure system along the Atlantic coast. The rain was accompanied by 50 mile per hour winds (80 kph). Travel delays were expected on Monday.
Private forecaster AccuWeather said the highest rainfall amounts of up to 4 inches (10 cm) would fall from Virginia to New York City late Sunday. New England would be hit harder early Monday into the morning rush hour. (Additional reporting by Karen Brooks and Daniel Lovering; Editing by Greg McCune and Stacey Joyce)