Whumpfing, Shooting Cracks And Other Direct Evidence

Snowpack assessment usually involves ambiguity. A small set of observations does not, and they are the ones most frequently recorded as having been noticed and overridden.

What a whumpf is

A whumpf is the sound and sensation of a weak layer collapsing beneath a slab under a person's weight, felt as the surface dropping slightly with a deep muffled thud.

It requires all three ingredients of a slab avalanche to be present: a weak layer, a cohesive slab above it, and enough reactivity for a person to trigger the failure.

The only reason it did not produce an avalanche is that the ground was not steep enough. On connected steeper terrain, the same collapse releases a slab.

Shooting cracks say the same thing

Cracks running away from a ski or a boot across the surface show that a slab exists and that failure propagates through the layer beneath it.

Propagation is the property that turns a small failure into a large avalanche, so a shooting crack is evidence about size as well as likelihood.

Cracks that appear and stop within a metre are weaker evidence than ones that run out of sight, but neither is a reason to continue onto steeper ground.

Recent avalanches are the strongest signal

Fresh avalanche activity on similar aspects and elevations is the most direct information available, because the snowpack has already demonstrated what it will do.

The relevant detail is which slopes ran, at what elevation and on what aspect, since that identifies where the problem lives rather than simply that it exists.

Old debris matters less, but a slope that ran during the current cycle indicates the layer is still capable of failing.

Why parties continue anyway

Incident reports repeatedly describe groups who heard whumpfing on the approach and carried on. The reasons are social rather than technical.

Commitment to a plan, distance already travelled, the presence of a confident member and the reluctance to be the one who raises a doubt all push in the same direction.

Recognising these pressures is part of formal avalanche education, precisely because the observations themselves are rarely missed. They are discounted.

How the evidence should be used

These signs are treated by educators as terrain-limiting rather than as one input among many. The standard response is to move to lower-angle ground unconnected to anything steep.

They also apply to the whole day rather than the moment, since a layer reactive at one point is likely reactive elsewhere on similar terrain.

Recognising and acting on them properly is taught on recognised avalanche courses alongside the regional forecast, and neither is optional for travel in avalanche terrain.