Prefrontal Squall Lines
Squall lines are lines of thunderstorms. When squall lines form in the warmer air that proceeds a cold front they are called pre-frontal squall lines. Pre-frontal squall lines may form as much as 100 to 300 km ahead of the font and may extend for 600 km along the front. Such lines may have super cells and intense storms.
Prefrontal squalls associated with trailing cold fronts produce the most dangerous and severe weather in the local area. They form most readily in late autumn, winter and early spring when the greatest air mass contrast is present.