Amazing cloud roll captured on camera

This amazing picture shows a rare phenomenon called a roll cloud which tend to form ahead of a cold front and can stretch for miles.
Most common when an advancing storm front causes moist air to rise, then cool to the point where it becomes a cloud known as the dew point.
When this happens along a front, a roll cloud can form, often with air actually circulating along the horizontal axis of the cloud.

It was also NASA's picture of the day a couple of days ago