A very ominous looking cloud known as a roll cloud crossed the skies Wednesday night.
Roll clouds are in the same family as shelf clouds except there are differences between the two.
Shelf clouds are associated with thunderstorms and severe weather. They are attached to the base of storms, but roll clouds are not.
A roll cloud is detached.
Due to the wind shear (the change in wind speed or direction height) these clouds often appear to be rolling horizontally.
They are often associated with the gust front (surge of cool dense air) ahead of a thunderstorm or sometimes just the passing of a cold front itself.
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