Weather is the carpenter that constructs the snowpack and makes it stable or unstable.
Knowing the past weather can give us a sense for current stability. Likewise, weather forecasts give us some indication of how stability might change.
1) Significant Precipitation:
Snow and/or rain adds weight to the snowpack. The harder it snows or
rains, the more difficult it is for the snowpack to adjust to the
additional weight or load and the more likely it is for the snowpack to
- Rain not only adds weight but can quickly cause changes in the snowpack leading to very unstable conditions.
- Sometimes in the early season with a weak snowpack it only takes a few inches of snow to create unstable conditions.
Wind blown snow often creates slabs on the leeward or down wind
sides of ridges and other terrain features. These wind slabs add weight to the existing snowpack. Fresh wind slabs almost always create unstable conditions.
3) Rising Temperatures:
Rapidly warming temperatures, especially in the spring, can lead to wet snow avalanches. Watch for signs of this change such as small point releases or pinwheels of snow rolling downhill.
Once again, it is a matter of timing. Riding in the spring often requires an early start while the snowpack remains mostly frozen. If the snowpack does not refreeze overnight, it can be unstable before you even leave the parking lot.