Wave clouds over Maryland and Virginia Thursday from the NASA Terra Satellite. Click image for a MUCH larger version.

The wave clouds on this image over Virginia are caused by winds flowing over the mountains. As the winds lift they form a cloud, and as they fall back down the air warms and dries out (and the cloud dissipates). These ripples happen because the air is fairly stable and does not want to go too high or low from its original height. So, after it goes over the mountains it falls down and oscillates up and down a few times, forming clouds as it reaches the top, and a clear slot when it reaches the bottom of the cycle.

Much like ripples in a pond when you toss a pebble in! I have written about these in 2012, and there is more info here.

You can see some snow cover in this image from Annapolis to the north as well.