By Judson Jones, CNN

A winter storm is blanketing Missouri and is expected to keep moving east this weekend.

As of 7 p.m. Friday, the National Weather Service's office in Weldon Spring, Missouri, reported about 5 inches of snow. Jefferson County Sheriff Dave Marshak said on Twitter on Friday there had been 50 accidents as of 5 p.m. CST. The Missouri Department of Transportation (MoDoT) on Twitter warned residents not to travel in the storm if it isn't necessary.

The storm has caused 53 arriving and 39 departing flight cancellations at St. Louis Lambert International Airport with more are expected into Saturday morning, the airport said on its website.

The University of Missouri men's basketball game at the University of South Carolina was also canceled Saturday because of weather-related travel issues, according to the team's Twitter account. The team followed up later on saying the game was "tentatively rescheduled for Sunday."

Missouri isn't the only state being hit by this traveling snow storm. It is poised to leave a blanket of snow this weekend over more than 1,500 miles from Denver to Washington.

Across the country's midsection, 50 million people are under a winter storm advisory, watch or warning. Washington and Baltimore were added to the list of advisories, watches and warnings Friday afternoon. Major cities in the zone, including St. Louis, could get more than 6 inches of snow.

The storm will gear up across central Colorado, then move east across the Plains. Some sleet and freezing rain arrived Friday morning in Missouri, with snow expected to fall by midday.

Significant snow due in St. Louis

The National Weather Service in St. Louis called for 8 to 12 inches of snow through late Saturday. It would be the most snow the city has had in a single storm since 2014 when a January blizzard dumped 10.8 inches.

There is about a 10% chance that St. Louis will get 15 inches or more of snow, according to the National Weather Service high-end forecast. It would be among the city's 10 greatest snowstorms -- landing at the No. 2 spot -- of all time if that happens.

"This storm may become an overachiever when it comes to snow and ice. The models this morning are 2 degrees colder than (Thursday), which will lead to higher amounts of snow and ice than were forecast (then)," CNN meteorologist Chad Myers says.

Travel may be treacherous along Interstate 70 from the Kansas City area to St. Louis and along I-64 from St. Louis to Louisville, Kentucky.

Half a foot of snow also is expected to fall across southern Illinois, Indiana and into Virginia. Cities such as Indianapolis can expect similar conditions as St. Louis, but as the storm moves east, the likely snowfall totals will be lower in major metro areas.

Washington, Baltimore and Philadelphia to see snow

Snow will reach the mid-Atlantic by late Saturday through Sunday, but snow totals will be lower there.

A few major East Coast cities are likely to see some impact, including Washington, Baltimore and Philadelphia, and there is a possibility for light accumulation in New York along the northern edge of the storm.

Washington and Baltimore will likely see 2 to 4 inches of snow and Philadelphia 1 to 2 inches.

The Appalachians will pick up some snow and sleet in Virginia, down through North Carolina and Tennessee. The southern mountains of North Carolina near South Carolina and Georgia will likely see more rain than sleet and snow.

There is a small chance that the southern Appalachians get enough freezing rain and sleet to turn into an ice event Saturday into Sunday.

On the storm's southside, more heavy rain will fall on the already saturated South.

The Southeast has seen abundant precipitation in December and January, and the additional rain could put a strain on rivers already high.