Tornadoes Likely in Plains

Two giant weather systems will be colliding there violently on Saturday.
Frigid, dry air covering the northwest is butting into an even larger mass of warm air rising up from the Gulf of Mexico laden with unstable moisture, CNN meteorologist Derek Van Dam said.
On one side, overnight lows plunge into the low 20s, where it's snowing in some places; on the other, daytime highs push into the 80s, while thunderstorms rumble by. A low pressure area is churning in between them.