"How many inches of snow does it take to make one inch of rain?" -- from Jesse Cox via Facebook
This is a great "Ask Tom Sherry" question because we'll hear about it all winter (provided this winter is just as snowy as last year).
In the most basic sense, think of it as a 10:1 ratio. According to Tom Sherry, "the average snow to liquid ratio is 10:1, meaning if 10 inches of snow fell and melted, it would produce 1 inch of water in the rain gauge."
But as well all know living in the Inland Northwest, there are many different types of snow that fall around here. Sometimes we get that wet, heavy snow that breaks your back when you have to shovel it from your driveway. Other times, it's the fluffy stuff that's great for skiing, but terrible for snowball-making.
It's when the light snow starts to fall that the ratio gets bigger. Tom says, "sometimes during a very cold, dry snowfall the snow to liquid ratio can be 20:1 and even as high as 30:1, meaning 30 inches of snow for 1 inch of water."
So, it varies constantly (making Tom's job tougher). He says, "accurately forecasting snowfall amounts is extremely difficult when based only on computer models and when the storm is still offshore. The best way to forecast snowfall amounts is to wait for the snow to begin falling. This combined with radar, satellite imagery, computer models and ground-based observations provide the most accurate forecast for snowfall totals."