@beaverbanker In the FAQ you can read “ New snow: Total snow accumulation in the next hours or days. To estimate the depth of snow, we use the ratio: 1mm of rain = 1cm of snow.” For instance the ECMWF model is giving the snowfall as water equivalent. https://codes.ecmwf.int/grib/param-db/144

Thanks, @idefix37! I've made a short article out of your answer: http://bit.ly/snow-depth-forecast-map