Weather is the carpenter that constructs the snowpack and makes the snowpack stable or unstable. Knowing what weather has occurred in the past can give us a sense if the snowpack is likely stable or unstable.  Likewise, forecasts indicate if anticipated future weather events are apt to make the snowpack more or less stable.

The following are weather conditions that almost always cause the snowpack to become unstable and liable to slide:

1) Significant Precipitation either snow or rain adds weight to the snowpack; if added very quickly the snowpack may not have time to adjust to the additional weight or load and it may fail and fracture. Rain falling on unconsolidated snow will almost always lead to unstable conditions.

2) Wind Blown Snow can create dense slabs on the leeward or down wind sides of ridges and other terrain features. When wind transports snow from one location and deposits it at another location it adds weight to the existing snowpack which almost often causes the snowpack to become more unstable and more apt to avalanche.

3) Warm Temperatures can make the snowpack less stable in the short term and more stable in the long term. Rapid warming typically causes snow layers to creep can cause the entire snowpack to glide downhill (see the snow "gliding" off the old car to the right). Creep and/or glide add stress to the snowpack and often make it less stable and more apt to avalanche. Prolonged temperatures well above freezing often saturate the snowpack with free water which increases the likelihood of wet snow avalanches.

In the absence of these factors, especially when temperatures are around freezing, the snowpack tends to become more stable and weak layers can strengthen.

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