Almost all of the rain and snow that falls on the American Heartland originates in the Gulf of Mexico. While the precipitation is triggered by fronts from the north or west, these storms bring little moisture with them. Arctic fronts are accompanied by cold, dry air and Pacific storms lose most of their moisture as they cross the Sierra Nevada and Rocky Mountains.
However, ahead of these fronts, warm, moist air moves up from the Gulf of Mexico. If low pressure zones along the fronts are potent enough to lift this moisture-laden air, precipitation occurs. So, as you gaze upon that snow in your yard, realize that it may have been lapping the shores of Cozumel last week!
