(Adds blizzard warning and flight cancellations in Colorado)
By Svea Herbst-Bayliss and Ross Kerber
BOSTON, Feb 23 (Reuters) - A weather system threatening New England with a third straight weekend of winter storms appeared to be weakening on Saturday night, promising less snowfall than expected.
Another storm was rolling out of the Rocky Mountains in the Western United States and could create blizzard conditions in Colorado over the weekend, according to a National Weather Service advisory.
Forecasters were also predicting blizzard conditions from Oklahoma through Missouri early next week when another snowstorm hits an area of the Northern United States from the Plains to the Great Lakes.
But by Saturday evening, the East Coast storm was moving more east and offshore than anticipated - potentially leaving areas like Boston with much less snowfall than originally expected, said Eleanor Vallier-Talbot of the National Weather Service in Taunton, Massachusetts.
"The further south you go, the less snow. Boston proper might not even see an inch of snow," she said. "The forecast models have been slowly but surely backing off this thing."
Much of the Midwest is already blanketed with snow, with more than a foot (30 cm) reported in Kansas on Thursday, forcing airports to cancel hundreds of flights and leaving motorists stranded on highways.
On Colorado's high plains, up to a foot of snow was possible overnight and throughout Sunday, with winds gusting up to 45 miles an hour (72 kph), said Frank Cooper, a meteorologist with the National Weather Service in Boulder.
A spokeswoman for the Denver International Airport said passengers could expect delays on Sunday as crews de-iced aircraft and cleared runways, and a Southwest Airlines spokeswoman, Olga Romero, said 46 flights in and out of Denver had been canceled until 11 a.m. on Sunday.
STATES OF EMERGENCY
The New England coast - from northern Connecticut to southern Maine - was expecting an extended mix of snow and rain, according to a National Weather Service advisory. Residents were taking it in stride.
"Look, it's winter, it's New England, it snows. Happens every time!" said Steve Scardino, a software sales executive and lifelong New Englander from Hopkinton, Massachusetts.
Farther north, near Portland, Maine, the heaviest snow was not expected until Sunday, with accumulations up to 8 inches (20 cm) farther inland.
The weather service said the storm may bring sleet and freezing rain to the Appalachians and mid-Atlantic states as well, with thunderstorms expected in the Southeast. It likely will dump rain from New York City to Philadelphia, it said. The storm barreled eastward after pummeling the Midwest during the week. In Kansas City, Missouri, Mayor Sly James said about 60 buses were stuck on snowbound streets on Friday, and even tow trucks were immobilized.
After a storm last week dumped some 14 inches (36 cm) of snow on Wichita, Kansas, and 11 inches (28 cm) on Kansas City, residents from Texas to Nebraska were bracing for another one early next week, according to AccuWeather.com.
Forecasters predicted heavy snow developing on Sunday night and increasing to a rate of 2 inches (5 cm) an hour from northern Oklahoma through central Kansas.
Missouri Governor Jay Nixon and Kansas Governor Sam Brownback declared states of emergency because of possible power outages and generally hazardous travel.
Drought-stricken farmers in the Great Plains, one of the world's largest wheat-growing areas, welcomed the moisture, although experts said even more rain or snow would be needed to ensure healthy crops. (Additional reporting by Kevin Murphy, Ian Simpson, Kevin Gray, Kewith Coffman, Steve Gorman and Chris Francescani; Editing by Peter Cooney and Jackie Frank)