 During fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall.Squall lines, or solid bands of strong thunderstorms, can form ahead of cold fronts and lee troughs due to the presence of significant atmospheric moisture and strong upper level divergence, leading to hail and high winds.When significant directional wind shear exists in the atmosphere ahead of a cold front in the presence of a strong upper level jet stream, tornado formation is possible.