Severe thunderstorms are a product of great turmoil (instability) in theatmosphere. Instability exists when cooling occurs aloft while the surface airheats up. This generates huge columns of rising air which, when enough moistureis present, can turn into towering storm clouds. The severity of athunderstorm is a product of its size and interaction with the jet stream.Wednesday, strong to severe thunderstorms are expected to impact the HighPlains from western Texas to Nebraska. The worst of the storms will causeviolent winds, large hail and may spawn a tornado.

Story by AccuWeather.com Expert Senior Meteorologist John Kocet.