We’ve all heard that each snowflake is unique in size and shape, but what about moisture content?
In geographic regions that rely on snowpack for their source water, like Denver, this is a very important issue. The National Weather Service calls the amount of water in snow the “snow ratio.” As a rule, 12 inches of snow can represent one inch of water in the Upper Midwest states. And, there are other variables that can determine the ratio, such as:
- Depth of the warm layer from the surface atmosphere into the snow producing cloud. The warmer it is (closer to freezing), the lower the snow ratio.
- Amount of ice in the snow producing cloud. If there are more super-cooled water droplets in the cloud, the snow ratio will be lower. If there is a higher amount of ice crystals, the snow ratio will be higher.
- If it is windy, snowflakes can fracture, losing their "lacy" structure and leading to lower accumulations, resulting in lower snow ratios.
- Deep cold, in general, promotes a higher snow ratio.
In other words, heavy, wet snow that falls when temperatures are higher has more moisture than the snow that falls on dryer, colder days.
The next time it snows in your neighborhood, picture your water system capturing the snowflakes – regardless of snow ratio – to fill its reservoirs.