- The sudden appearance of scud indicates a forming wall cloud
- W022455S
- A thunderstorm has been growing to the left in steps (propagation) as it moves forward. Below the rain-free base are two scud clouds which have formed in mid-air from entrained moist outflow in the rising air entering the base. A sudden appearance of rising scud below a storm base often indicates that a wall cloud or lowering will form.
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