Extratropical cyclone, Lake-effect snow, and Rainband

Extratropical cyclone, Lake-effect snow, and Rainband

Preferred region of heavy snowfall ("Banded Snowfall") around the comma head of a wintertime low pressure area, shaded in green

Lake-effect snow bands near the Korean Peninsula

Extratropical cyclones can bring cold and dangerous conditions with heavy rain and snow with winds exceeding 119 km/h (74 mph),[2] (sometimes referred to as windstorms in Europe). The band of precipitation that is associated with their warm front is often extensive, forced by weak upward vertical motion of air over the frontal boundary which condenses as it cools and produces precipitation within an elongated band,[3] which is wide and stratiform, meaning falling out of nimbostratus clouds.[4] When moist air tries to dislodge an arctic air mass, overrunning snow can result within the poleward side of the elongated precipitation band. In the Northern Hemisphere, poleward is towards the North Pole, or north. Within the Southern Hemisphere, poleward is towards the South Pole, or south.

Within the cold sector, poleward and west of the cyclone center, small scale or mesoscale bands of heavy snow can occur within a cyclone's comma head pattern. The cyclone's comma head pattern is a comma-shaped area of clouds and precipitation found around mature extratropical cyclones. These snow bands typically have a width of 20 miles (32 km) to 50 miles (80 km).[5] These bands in the comma head are associated with areas of frontogenesis, or zones of strengthening temperature contrast.[6]



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