58 million Americans across 20 states on alert for severe weather

At least 58 million Americans across 20 states are on alert for severe weather as a major winter storm is expected to bring heavy snow, high winds and a threat for tornadoes from Colorado to Alabama through Thursday.

A tornado watch was issued Thursday morning for parts of Kentucky, Alabama and Tennessee, including Memphis, Tennessee; Little Rock, Arkansas; and Paducah, Kentucky.

A new tornado watch was issued for parts of Mississippi, including Jackson, Meridian and Hattiesburg, which will remain in place until 5 p.m. local time. Wind gusts could reach 70 mph.

Winter storm warnings stretch from New Mexico to Illinois for a swath of heavy snow. High wind warnings remain in effect across the Southwest and wind advisories are in effect across the Great Lakes.

The storm will continue to move east on Thursday, with more severe weather expected from the Gulf Coast all the way to Ohio.

There could be damaging winds and tornadoes from Texas to Alabama and up to Ohio. The highest tornado threats on Thursday will be in Mississippi, Alabama and Tennessee.

Whiteout conditions are likely across the Texas and Oklahoma panhandles, Kansas and southern Nebraska. Snowfall rates could reach 1 to 2 inches per hour accompanied with high winds.

Overnight Wednesday into Thursday, hail larger than golf balls hit Arkansas and Tennessee.

Damaging winds near 70 mph were reported in Oklahoma.

A swath of heavy snow is expected from Colorado to Michigan through Thursday. Some areas, especially across Kansas and Nebraska, could see 6 to 12 inches of snow.

Chicago could see up to 5 inches of snow; this could be their biggest snowstorm of the season if the system shifts any further south.

In Denver, almost 40% of Wednesday's flights were delayed or canceled due to the heavy snow.

Tornadoes were possible Wednesday into Thursday morning from Arkansas to Tennessee and northern Mississippi. The National Oceanic and Atmospheric Administration said there was a possible tornado in Gibson County, Tennessee, early Thursday.

On Thursday afternoon, severe storms forecast to blossom in Mississippi and Alabama where a few strong tornadoes are possible.

Ahead of the storms, there were record warm temperatures in the Midwest and the East Coast. Numerous record warm temperatures were expected to be broken Wednesday and Thursday before more seasonable weather returns on Friday.

Some 200 records could be tied and broken through Friday.