Thunderstorms develop in warm, moist unstable air. Unstable air means that the air temperature cools rapidly with height. Severe thunderstorms develop in a myriad of different places and are intensified by cold fronts, drylines, upslopes and the like. These thunderstorms often produce large hail and strong winds, and some ultimately produce tornadoes.

Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.

Along the High Plains of the United States, including the Front Range region of the Rocky Mountains, intense thunderstorms can occur when air in the lowest few thousand feet of the atmosphere is pushed westward toward higher terrain. This phenomenon is known as "upslope flow," and is most commonly referred to in the media as simply an "upslope." In our area, the source for our upslope air is usually eastern Colorado, Kansas, or Nebraska.

Definitions and Introduction | What Causes Tornadoes? | How Do Tornadoes Form? | Characteristics of Tornadoes | Tornado Myths