The current snowpack is faceted top to bottom - if you can even call it a snowpack. In some places there are thin to thick suncrusts, other places the snow surface is recrystallized particles. Despite the thin coverage, as long as the ground has an insulating blanket of snow, the ground is almost always warm--near freezing--even with very cold air temperatures. Depth hoar forms from large temperature gradients between the warm ground and the cold snow surface. Since the snow cover is about 12 inches in most places, there is a huge change in the snow temperature from the ground (32F) to the snow surface, which in the morning ranges from 14 to 26 F.
The thin snow cover is subject to high temperature gradients and without snow on top, the depth hoar will not strengthen as it does when there is snow sitting on top of depth hoar. There are several suncrusts sandwiched between faceted layers. Each suncrust represents the period of time between storms. The facets are the storm snow that changed into weak facets under strong temperature gradients combined with shallow snow and cold temperatures. Forecasters never underestimate the persistence of faceted snow as a weak layer and depth hoar avalanches can be large and scary. It commonly propagates long distances, around corners and easily triggered from the bottom--your basic nightmare. Walter Rosenthal took this picture of a large depth hoar avalanche along the Cliffs on Mammoth Mountain.