A shelf cloud is similar to lenticularis cloud, but on a much larger scale. A shelf cloud sometimes forms ahead of a severe, long-lasting thunderstorm such as a mesoscale convective system (MCS), multicell or supercell. Cold downdraft air surges out along the surface and lifts the (usually conditionally stable) warm air ahead of the storm up to condensation level. A smooth shelf-like cloud forms, skirting the thunderstorm. The shelf cloud is usually accompanied by a gustfront and sometimes also a roll cloud.
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