A major storm sweeping the US is expected to bring heavy rain, snow to the East Coast this weekend

NEW YORK -- A winter weather system moving through the U.S. is expected to wallop the East Coast this weekend with a mix of snow and freezing rain from the southern Appalachians to the Northeast -- although it's too early to say exactly which areas will get what kind of precipitation and how much.

Details on the storm's path should firm up this week as the Pacific system moves through Colorado and New Mexico on Thursday and into Texas and the Southeast before moving up the East Coast, said Tony Fracasso, a meteorologist with the National Weather Service's Weather Prediction Center in College Park, Maryland.

"It's still a few days away, so we'll have to hash out the storm track -- where the precipitation falls, and how long the cold air can stay," he said Wednesday.

Major U.S. cities accustomed to white winters -- such as Boston, Washington, D.C., and Philadelphia -- didn't receive much snow last year because of a lack of cold air.

The National Weather Service in New York City posted on social media platform X on Wednesday that the city has a low probability of snow and sleet Saturday into Sunday, with significant snowfall expected in areas west and north of the city.

Earlier this week, the NWS of New York said that 2023 would go down as the city's "least snowiness" year, with just 2.3 inches measured in Central Park.

Winter storms in a warming world

The snowfall drought affecting parts of the eastern U.S. can be attributed to a number of factors, said Chris Stachelski, regional program manager for climate services and observations at the National Weather Service's eastern region headquarters.

Temperatures have been warmer than normal, making it hard for precipitation to fall as snow. Some storms that recently tracked through the northeast were carrying warm air from the south and moisture that fell as rain.

The influence from El Nino also played a role in the lack of snow in this region by preventing cold air from getting into the East long enough to interact with moisture that storms are bringing, which is key for precipitation to fall as snow, Stachelski said.

The snowfall drought is setting records across the region. For the number of consecutive days with less than an inch of snow, Philadelphia reached 704 days through Thursday with a prior record of 661 days ending on Dec. 15, 1973. NYC reached 690 days through Thursday, with a prior record of 383 days on March 21, 1998. Baltimore reached 706 days through Thursday, a record, with a prior record of 672 days on Dec. 25, 2012.

"It is almost exactly as it has been predicted by climate models ... it will snow less frequently and more of the storms will dump rain as opposed to snow in the U.S. northeast," said Pedro DiNezio, associate professor of oceanic and atmospheric science at the University of Colorado Boulder. Precipitation is still occurring during fall and winter, but it is more commonly falling as rain than snow.

DiNezio said that a warmer atmosphere can hold more moisture, which means that when temperatures do get cold enough, winter storms could produce even more snow than normal.

"All these (atmospheric) relationships that we've seen over time are being thrown out of the window by the extreme weather and climate that we're experiencing," DiNezio said. "You don't need to be a scientist to sense that something is off."