Interactive Snow Water Equivalent (SWE) and Snow Depth
Unlike snow depth, which can blank out during heavy snowfall events and settles between storms, SWE is a more stable metric of how much snow accumulated during a storm and what the snowpack looked like before it came through. It represents the amount of liquid water contained (or added) to the snowpack in inches, which can directly be translated into load applied to the snowpack structure.
A good rule of thumb with SWE for Montana SNOTEL sites is to assume a ratio of 10:1 or higher during the colder winter months if you want to estimate how many inches of snow you might find at the SNOTEL site. That means if 1.0" of SWE is added to the snowpack, 10 or more inches of snow may have accumulated. "Cold Smoke," which is very low-density new snow (95% air, 5% water), equates to a 20:1 ratio. During the fall and spring months, when temperatures are typically warmer during storms, you might consider using a lower ratio of 8:1 or lower.
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