Anvil clouds, also known as cumulonimbus, are storm clouds. These storm clouds were rather small, compared to the usual. As a storm that passed by Fargo to the west, missing Fargo, while heading southeast, I decided to get a time 4K lapse shot. At 30x real time, you can easily see the clouds passing by and even building up. All photos used ISO 200, f4, 14000 second exposure at 12 mm with a 0.75 dynamic range exponent.