Also: Whumpfing, Collapsing, Cracking, Settling (misused)
When there is a weakness buried in the snowpack which has a lot of air space between grains and which is weak under compression a "whumpf" sound may be heard when this weak layer fails and air is compressed out of it.
This may or may not be accompanied by the appearance of shooting cracks.
This sound, with or without cracking, usually indicates a highly unstable situation. The types of failures which produce this "whumpf" sound are ones which can propagate great distances, including upslope from a runout zone.
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