A powerful winter storm crept across the upper Midwest on Friday, tracking on a circuitous path that forecasters said could create a cascade of power outages, hazardous travel conditions and deepening supply-chain problems across a vast section of the country extending from the South to the East Coast.
The sprawling weather system prompted winter storm warnings and watches from North Dakota down to northern Mississippi and across to Raleigh, N.C., and areas of western New York.
But some ambiguity remained over how much snow, ice and rain the storm could bring in the coming days, especially in the Northeast and the Mid-Atlantic, where another storm caught transportation officials off guard and stranded hundreds of drivers in Virginia this month.
“This is going to be a major setback for several days for companies trying to move products around the country just due to the scale of the storm,” Jonathan Porter, the chief meteorologist for AccuWeather, which is based in State College, Pa., said on Friday.
Inland portions of the Appalachians extending from western North Carolina and western Virginia to western Pennsylvania and upstate New York could get 12 to 18 inches of snow during the storm, Mr. Porter said. The rate of snowfall could be more than an inch an hour in some places, which could cause significant travel delays.
On Friday, Gov. Ralph S. Northam of Virginia declared a state of emergency and ordered the activation of that state’s Emergency Operations Center.
“This upcoming weather system is likely to include additional downed trees, more electrical outages, and significant impacts on travel conditions,” Mr. Northam said in the declaration.
In the Northeast, the storm is expected to bring one to three inches of snow to Washington, Philadelphia, New York and Boston from midday Sunday to Monday morning, Mr. Porter said, noting that the precipitation would most likely turn to rain and could vary in amount if the storm shifts.
He warned that the storm could produce wind gusts of up to 70 miles per hour along the coast.
In the South, ice loomed as a major concern for meteorologists, who said that northeastern Georgia and the Carolinas were expected to bear the brunt of freezing precipitation on Saturday night into Sunday.
“While much is going to be said about the snow, we’re also raising the alarm of the ice storm that’s going to occur across the Carolinas,” Mr. Porter said. “It looks like that’s a recipe for extended power outages and tree damage in those areas.”
Some airports and transportation departments were already bracing for potential travel issues.
David Roth, a senior forecaster with the National Weather Service, said Thursday evening that meteorologists expected the forecasts to evolve.
“There’s more uncertainty than usual,” Mr. Roth said. “When we’re dealing with the difference between rain and sleet and freezing rain and snow, subtle changes make a big difference.”
By early Friday, snow was falling across parts of North Dakota, Minnesota and Wisconsin, according to the Weather Service.
“This snow will combine with gusty winds to produce slippery, snow covered roads and significantly reduced visibility,” the Weather Service said on Twitter. “Travel will likely become hazardous to dangerous at times.”
The storm is expected to move southeast later on Friday toward Iowa, where some areas could get six to 10 inches of snow, according to the Weather Service.
Southwest Airlines warned on Thursday that travelers passing through or from Des Moines International Airport could see flights delayed, diverted or canceled. Other cities under the airline’s travel advisory include St. Louis, Omaha and Kansas City, Mo. American Airlines and Delta made similar announcements related to the weather.
The Federal Aviation Administration advised travelers on Friday to check with their airlines for storm-related delays and cancellations.
The storm could bring wintry weather to parts of western Kentucky and southeast Missouri by Friday night, with snowfall amounts of up to four inches possible, according to the Weather Service office in Paducah, Ky.
In addition to exacerbating supply-chain issues, forecasters warned that the storm could hamper coronavirus testing operations in many areas and place additional strain on health care workers. The storm could also further complicate recovery efforts in Kentucky and other areas that were ravaged by a series of deadly tornadoes last month, the forecasters said.
Nashville could get three to six inches of snow starting around midday on Saturday, with higher snowfall amounts north of the city in what has already been a snowy winter, meteorologists said.
“Nashville may have more snow this winter than both Milwaukee and Chicago,” Mr. Porter said. “That’s pretty impressive.”
On Saturday, the storm system is expected to continue moving southeast toward upper South Carolina, northeast Georgia and western North Carolina. The Weather Service said mixed precipitation was possible in the area, with up to 10 inches of snow possible, along with possible accumulations of ice.
Dave Nadler, a meteorologist with the Weather Service office in Peachtree, Ga., said in a briefing that some ice accumulation in northern Georgia could be significant.
“We are looking at the potential for a significant winter storm,” Mr. Nadler said. “The looks of that and the confidence of that is starting to increase.”
The uncertainty in the forecast could be unnerving for those who live along Interstate 95 in Virginia, after a snowstorm this month left hundreds of drivers stranded in their vehicles for more than 24 hours.
The Virginia Department of Transportation was not taking any chances, and on Thursday its crews began spraying portions of I-95 with a solution of salt and brine, which helps prevent ice from bonding to roadways.