Editing Squall line (section)

{{About|a line of thunderstorms|a sudden, sharp increase in wind speed|squall}}
{{Short description|Line of thunderstorms along or ahead of a cold front}}
{{Merge from|Narrow cold-frontal rainband|date=April 2025}}
[[File:Pehrcn07212003.gif|thumb|A [[weather radar]] image of a [[mesoscale convective vortex]] (MCV) over Pennsylvania with a leading squall line]]
A '''squall line''', or '''quasi-linear convective system''' ('''QLCS'''), is a line of [[thunderstorms]], often forming along or ahead of a [[cold front]]. In the early 20th century, the term was used as a synonym for cold front (which often are accompanied by abrupt and gusty wind shifts). Linear thunderstorm structures often contain heavy [[precipitation (meteorology)|precipitation]], [[hail]], frequent [[lightning]], strong [[straight-line wind]]s, and occasionally [[tornado]]es or [[waterspouts]]. Particularly strong straight-line winds can occur where the linear structure forms into the shape of a [[bow echo]]. Tornadoes can occur along waves within a [[line echo wave pattern]] (LEWP), where mesoscale [[low-pressure area]]s are present. Some bow echoes can grow to become [[derecho]]s as they move swiftly across a large area. On the back edge of the [[rainband]] associated with mature squall lines, a [[wake low]] can be present, on very rare occasions associated with a [[heat burst]].