This kind of weather wouldn't be so unusual if it were spring or
fall, but there seems to be something different about the jet
stream -- the flow of air that divides cold and warm air -- this
year, said CNN meteorologist Dave Hennen. The jet stream flows
west to east, typically at 100 mph, although its wind speed can
often top 200 mph. If you visualize it as a line with a pattern
of bumps and dips, those curves have been much taller in
January, Hennen said. "We've always had dips and valleys in the
pattern, but this year they have been very large," he said.
"It's also unusual that you have that much warm air that far
north at this time of year. It's almost unheard of." The
unseasonably warm weather has been good for going to the park,
but it also led to the severe weather that developed Tuesday
night and Wednesday as cold air moved east, clashing with the
warm, wet air. "Where there is so much moisture in the air, the
cold air won't let it stay there," CNN meteorologist Chad Myers
said. "The cold air pushes i