Snow has been falling from the Plains into the Great Lakes today, and more is ahead for this weekend. Several storm systems will be moving through the nation over the next few days, bringing wintry weather and travel headaches. Winter weather alerts cover more than a dozen states from near Glacier National Park through the Plains to Lake Ontario. The heaviest snow will be found in the mountains of the west and in the Northeast, near the Great Lakes, where more than a foot may accumulate into early next week.   Ice will be a concern as well, with a narrow stripe forming ahead of a front from Oklahoma though the Ohio Valley and into New England. Two storm systems will bring the significant snow to the Northeast. A low pressure center is moving into the region now, putting down the first round of snow. The second system will move out of the Southeast and into the Middle Atlantic and Northeast Sunday through Monday. It will create the areas of ice and additional snowfall accumulations. For WeatherNation: Meteorologist Mace Michaels