We shared with you some of the roll cloud photos from this morning, but none as dramatic at this.

Click to enlarge (National Weather Service)

Taken at the National Weather Service forecast office in Sterling, Va., like an advancing army, the roll cloud fronts the office.

“An outflow boundary from the showers associated with the cold front produced a very well defined roll cloud that passed over our forecast office this morning just before 7:30 am.,” explains the NWS-Sterling Facebook page. “Here’s a picture of it as it approached (moving toward the camera)… it was moving very fast!”

Related: Clouds: The weirdest of the weird | Is that a tornado? Wall, scud, shelf and other scary looking clouds