The U.S. Upper Midwest and Plain States received widespread thundersnow, winds gusts close to 70 mph and over 2 feet of snow in spots, and led to hundreds of canceled flights at Denver International Airport, and hundreds of schools canceled classes in Minnesota, Nebraska and South Dakota as reported by CBS. These extreme events are blamed on stronger than normal contrasts for spring as warm and moist air surges north from the Gulf of Mexico and interact with cold winter air still in place, but heightened by the so called "Arctic amplification." This phenomenon led recently to record-breaking heat in the Arctic, including Alaska, and produced warmer-than-normal air that stretched from Alaska east through Canada to Greenland, which displaced a cold pool of air southward into the U.S. mainland, and hence, the storm moving across the Upper Midwest and Plain States had an excess of warm-cold contrast to feed off of as reported by CBS.