Midnight update: The National Weather Service forecast for the York area still calls for 4 to 8 inches of snow -- with the highest amounts in the south part of the area, diminishing farther north.
A winter storm that begins before daybreak in the Laurel Highlands is expected to reach York and vicinity by mid-morning Tuesday and continue through early Tuesday evening, with temperatures not rising above 20 degrees.
The Weather Service characterizes Tuesday's weather as potentially "dangerous" -- cold with snow and wind gusting to 25 mph reducing visibility and snow-covered roads making travel hazardous.
9:30 p.m. update: The southern part of York County can expect the most snow accumulation during Tuesday's storm, according to the National Weather Service.
"The storm is passing south of the state, and the further north you go, there will be less snow. The further south, the more snow," said Tony Mach, a meteorological technician with the National Weather Service in State College.
At about 9:20 p.m. Monday, Mach said the National Weather Service is sticking by its prediction of 4 to 8 inches in York County. Temperatures will remain around 20 degrees on Tuesday, he said.
"There's not going to be much of an increase in temperature tomorrow. The real cold will be tomorrow night," Mach said.
Overnight, between Tuesday and Wednesday, temperatures will hover around 5 degrees, he said.
6:30 p.m. update: The winter storm warning from the National Weather Service in State College remains in effect from 4 a.m. to 10 p.m. Tuesday, and the predicted snow accumulation in the York area has been increased.
The NWS now says snow accumulation is expected to be 4 to 8 inches. The chance of snow is close to 100 percent.
Tonight's temperatures are forecast to drop to lows around 20 degrees, with northwest winds 10 to 15 mph. Temperatures are not expected to rise above 20 degrees Tuesday. .
1:45 p.m. update: York County has been upgraded to a winter storm warning from 4 a.m. to 10 p.m. Tuesday, the National Weather Service said.
York, Adams, Lancaster, Franklin, Fulton, Somerset and Bedford counties are covered by the warning.
The area will receive 5-7 inches of snow, hitting the lower Susquehanna valley in the mid- to late morning on Tuesday, the NWS said.
The snow is expected to continue through early Tuesday evening.
The wind will also pick up in the afternoon, ranging from 10 to 20 mph with gusts up to 25 mph, the weather service says.
Previous story: Get that snow shovel ready: An arctic cold front will come through Monday night and bring some wintry weather.
Snow is predicted to start Tuesday morning and last throughout the day, said Craig Evanego, a meteorologist with the National Weather Service in State College.
York could see 4 to 8 inches, he said, with heavier amounts in the southern part of the county.
The white stuff will linger throughout the day and stop by Wednesday, Evanego said.
Coupled with very low temperatures, the snow will probably be fluffy, he said. Winds will also pick up after the snow and continue into Wednesday, he said.
Cold: January has brought temperatures from 0 to 50 degrees so far this year.
And this week, York can expect to get down to the single digits again.
Monday will see highs in the low 40s and a low around 19, according to the forecast. After that, York is in for a cold week, Evanego said.
"Temps aren't really going to budge much from the Monday night low," he said.
Tuesday's highs will be in the low 20s before temperatures dip into single digits at nighttime, according to the forecast. Wednesday will see highs around 17 degrees and a low around 8 degrees, the forecast says.
Thursday and Friday temperatures are expected to hover in the mid-20s.
So far, January has an average temperature of 26.3 - about 4 degrees below normal, according to the National Weather Service's climate data in Harrisburg.
The next snow event on the radar is slated for Thursday, although it should be lighter than Tuesday's precipitation, Evanego said.