Complex sentence: A squall line is a line of severe thunderstorms that can form ahead of a cold front and can contain heavy precipitation, hail, frequent lightning, dangerous straight line winds, and possibly tornadoes and waterspouts.
Split into simpler sentences: A squall line is a line of severe thunderstorms that can form along or ahead of a cold front. It contains heavy precipitation, hail, frequent lightning, strong straight line winds, and possibly tornadoes and waterspouts.