Scud clouds do not signify severe weather, but are commonly mistaken for wall clouds, funnel clouds or tornadoes.   How can you tell if a cloud feature is scud or something more significant?  First, look to see if the cloud is attached to the storm base.  If it is not, it is likely scud.  Second, look at the motion within the cloud.  The only motion ever evident in scud clouds is slow upward motion (if anything), which easily distinguishes them from the very rapid rotation in a funnel cloud or tornado.  Also, scud clouds usually change shape or dissipate within a minute or two, which distinguishes them from wall clouds which are persistent features, and can last for tens of minutes.  If you still aren't certain if an ominous cloud lowering is scud or a tornadic feature, call it in anyway! Just be sure to describe what you see exactly, and clarify that you aren't sure what it is.