Snow expected across nation
(CNN) -- A winter storm 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 is calling 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.