Albedo - The percentage of solar radiation that is reflected by a surface. An albedo of 100 means that 100% of the sun's energy is reflected back to space, while an albedo of 0 refers to a surface that absorbs all the sun's energy. The whiter the surface is, the higher the albedo will be. Snowpack has a high albedo.

Rain Gauge - An instrument used to measure the amount of rainfall that occurs over a specific site. A standard rain gauge can measure up to 8 inches. The first known device that was used for measuring rainfall was invented in Korea in 1441.

Back Door Cold Front - Most cold fronts in the Northern Hemisphere come in from the north, northwest, or west. They are usually found on the backside of a low pressure system. Back door cold fronts come in from the northeast or east, and are often driven by Canadian based high pressure systems.

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'.

Cloud Modification - The introduction of foreign particles by humans into a cloud to gain a desired effect. This is oftentimes called cloud seeding. Silver iodide is a common substance that has been used in cloud seeding. The desired impact is to increase the amount of precipitation and/or reduce the threat for hail that falls from the cloud. It is not known how effective cloud modification has been since it was first introduced in the late 1940s.

Diamond Dust - A type of precipitation composed of slowly falling and very small, ice crystals which often seem to float in the air. It may fall from a high cloud or from a cloudless sky. It only occurs during frigid temperatures. Diamond dust is observed around 316 days a year in parts of Antarctica.

Arctic Front - The semi-permanent, semi-continuous boundary that separates the deep, cold arctic air from the shallower, less frigid polar air of the northern latitudes. Major shifts in the polar jet stream can drive arctic fronts southward into the mid-latitudes during the winter season.