- Behind a gust front, with clumps of scud along the boundary
- W990731S
- A constant stream of windy outflow air pushes forward under and behind a gust front axis, picking up loose dirt and lofting it. The boundary has several clumps of scud along it, similar to teeth or lobes when viewed from the other side. Some of the dust is entrained by updrafts and lofted to the cloud base.
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