A number of severe thunderstorm watches are in effect this afternoon, from Montana's border with Canada all the way to the South Carolina coastline! A large, broad trough situated west of the Rockies is ejecting energy eastward this afternoon, serving as the spark for severe storms over the highly unstable atmosphere of the northern Plains. The trough will continue to progress eastward, leading to an enhanced severe weather threat for the Dakotas and Minnesota again tomorrow. This is not dissimilar to the event that transpired last weekend, when a record-sized hailstone fell over Vivian, SD on July 23. Chad Cowan of ChaseTheStorms.com and best-selling author of The Stormchasers Jenna Blum were among the chasers in the area, and he was able to document the same storm later in its life cycle -- check out the ridiculous structure!!!