The majority of the country is being slammed by a massive cold front racing across a corridor from Maine to Texas, sending heavy rain marching toward the East Coast, as a severe weather threat takes aim at the South through Wednesday. Meanwhile, the front has created a rare May snowstorm ongoing across the Central Rockies, including Denver. A swath of heavy rain soaked a path from Arkansas to upstate New York early Wednesday as the front pushed east, expected to eventually reach much of the coast later in the day. Some of those storms across the South could develop into severe thunderstorms later Wednesday morning, with a more significant threat developing Wednesday evening.…