page_title: Squall line
section_title: Depiction on maps
hierarchical_section_title: Squall line / Theory / Depiction on maps
caption_attribution_description: English: How a squall line is dipcted by the NWS on weather maps.
context_page_description: A squall line or quasi-linear convective system is a line of thunderstorms forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts. Strong straight-line winds can occur where the squall line is in the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern, where mesoscale low-pressure areas are present. Some bow echoes which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rainband associated with mature squall lines, a wake low can be present, sometimes associated with a heat burst.
context_section_description: Squall lines are depicted on National Weather Service surface analyses as an alternating pattern of two red dots and a dash labelled "SQLN" or "SQUALL LINE".
caption: How a squall line is depicted by the NWS on weather maps
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