Estimate snowfall from precipitation and temperature.
Snow depth is liquid precipitation multiplied by a snow-to-liquid ratio that depends strongly on temperature. The often-quoted ten-to-one rule only holds near minus 2 to minus 4 degrees; wet snow near freezing compacts to seven-to-one, while very cold dendritic crystals can exceed twenty-to-one. That is why the same forecast rainfall can produce anywhere from eight to thirty centimetres of snow.
Snow depth from liquid equivalent
Snow depth in cm = precipitation in mm x snow-to-liquid ratio / 10; accumulation rate = depth / duration
Only at around minus 2 to minus 4 degrees. Warmer snow is denser and colder snow much fluffier, so the ratio ranges from about 7:1 to over 25:1.
Cold crystals are intricate and trap far more air, so the same water content occupies a much greater depth — though it also compacts and blows around more easily.
Considerably for disruption. Two centimetres an hour overwhelms clearance operations even when the storm total is modest.