Refraction - The process by which light slows down when passing through a medium, resulting in a bending or change of direction. Refraction explains many atmospheric phenomenon that occur in the sky. For example, sun dogs are seen due to the refraction of sunlight that occurs when there are numerous ice crystals suspended in the sky. Rainbows are also produced by the refraction of sunlight when it passes through raindrops.

Indian Summer - A period of unseasonably warm and sunny weather that occurs from late September to mid November. In parts of the country, the first killing frost of the season must occur before a late autumn warm spell can be coined 'Indian Summer'.

Mist - A visible collection of tiny water droplets suspended in the atmosphere that can reduce visibility to as low as 5/8 of a mile. It does not reduce visibility as much as fog and is often confused with drizzle. Drizzle falls to the ground, while mist hangs in the lower atmosphere.

Loaded Gun (Sounding) - A description of the state of the atmosphere that is characterized by extreme instability. Loaded gun soundings contain a stable layer, called a cap, that must be broken through in order for the instability to be unleashed. If the cap is overcome, rapid development of strong to severe thunderstorms can be expected.

Storm-relative velocity - A radar view which allows a meteorologist to view wind speeds within a thunderstorm. The term storm-relative means that the storm's overall motion is subtracted from the data to give a clearer picture of what the winds are doing within the storm. This display is helpful trying to diagnose if the storm itself is rotating. It can also be used when trying to determine if a tornado is present within the storm.

Supercell Thunderstorm - A relatively long-lived, large and intense storm cell characterized by exceptionally strong updrafts that can exceed 100 mph. Supercell thunderstorms have updrafts that rotate, which gives them the ability to remain intact for long periods of time. Most of the strong to violent tornadoes that develop are associated with supercells.

Lenticular clouds - The scientific name is altocumulus standing lenticular clouds. These lens shaped clouds are the most common cloud type to be mistaken for UFO's. They are most common near mountain ranges, as they form when strong winds blow up and over the top of a mountain range. Even though the winds within these clouds are moving very quickly, the cloud formation itself remains stationary. The presence of a lenticular cloud signifies an area of severe turbulence in the atmosphere, as pilots avoid them when possible.