The jet stream that circles Earth's north pole travels west to east. But when the jet stream interacts with a Rossby wave, as shown here, the winds can wander far north and south, bringing frigid air to normally mild southern states. NASA/GSFC hide caption

itoggle caption NASA/GSFC

They're down there somewhere: The Great Lakes as seen from space on Wednesday. Lake Ontario, which has less ice than the others, is at the lower right. A bit of open water can be seen in Lake Superior, at the upper left. CoastWatch.glerl.noaa.gov hide caption

itoggle caption CoastWatch.glerl.noaa.gov

Last week in Indianapolis, the Kehoe children — from left, Maria, Anthony and Veronica — played with shaving cream as their mother Joanne tried to keep them occupied when the weather outside was awful. R. Brent Smith/AP hide caption

itoggle caption R. Brent Smith/AP

Not a good day for a drive: A Georgia Department of Transportation sign warned motorists in Norcross Wednesday morning, and few were on the roads. John Amis/AP hide caption

itoggle caption John Amis/AP

This car was navigating a snowy road early Tuesday in Fort Payne, Ala. The wicked winter weather there is spreading across the Deep South. Hal Yeager/AP hide caption

itoggle caption Hal Yeager/AP

Jan. 29, 2014: Traffic is snarled along the I-285 perimeter north of Atlanta's metro area after an ice and snow storm passed through. Officials hope such a scene isn't repeated. David Tulis/AP hide caption

itoggle caption David Tulis/AP

This man stopped to take pictures of the snow-covered trees in Manhattan's Central Park on Tuesday. Seth Wenig/AP hide caption

itoggle caption Seth Wenig/AP

Winter: Do you wish it was over? Or is weather like this just great? (A scene in Queens, N.Y., on Monday.) Matt Rourke/AP hide caption

itoggle caption Matt Rourke/AP

A winter storm dumped snow Tuesday along Interstate 20/59 near downtown Birmingham and on other parts of central and southern Alabama. Tamika Moore/Al.com /Landov hide caption

itoggle caption Tamika Moore/Al.com /Landov