The process and rate of adding weight to the snowpack.
Loading occurs from snowfall, rain, or wind-transported snow. Snowpacks, and thus avalanche conditions, are sensitive to the amount of loading and also the loading rate. The snowpack is like someone lifting weights at the gym. If you add too much weight too quickly, it may fail. If you add small amounts of weight incrementally over a long time span, it is more likely to gain strength and adjust. Weak snowpacks will fail under smaller loads than strong snowpacks. Forecasters monitor the amount and rate of loading using a variety of tools and instruments.
Loading rate refers to the amount of snow or snow water equivalent that is added to the snowpack over a given amount of time. Avalanches are more likely during rapid loading. Critical loading rates vary depending on the state of the snowpack, but in general, a foot of new snow, an inch of snow water equivalent, or heavy wind transport in the past 24 hours are all red flags warning of excessive loading. An inch of water may not seem like much weight if you’re looking at it in a water bottle, but it equates to 150 tons across the dimensions of a football field. That’s a lot of load to suddenly add to an avalanche starting zone!
Rain also loads and adds stress to the snowpack.