Snow to Liquid Ratio

We knew it had to happen eventually.  After all, it is the beginning of December.  Our first snowfall of the season comes this weekend with 1" to 2" of snow falling by Sunday afternoon.  Forecasting snowfall can be tough.  Especially when it's the first of the winter season.  There are many elements that meteorologists look at when trying to predict how much snow will fall: temperature, moisture, dry air, how far up in the atmosphere the air is saturated, melting on contact, etc.

One such factor I'm sure many of you have heard of is the snow to liquid ratio.  This is important to look at because the amount of moisture that falls with a system (or a model is predicting) correlates to just how much snow one particular area will receive.

The 'average' snow to liquid ratio is 10:1.  This means if 10 inches of snow were to fall and we were to melt all that snow it would equal one inch of water.  But we know most snow storms around here are anything but average.  Dry snow, or the very fluffy snow, has a higher snow to liquid ratio.  These snowflakes tend to be smaller in size and usually don't make good snowballs because you can't compact the snow.  With this type of snow there doesn't have to be a major storm system to get high totals.  Because it is so much more fluffy, it can add up pretty quick.  A wet snow or 'heart attack' snow has a lower snow to liquid ratio because it holds more moisture.  These snowflakes are usually bigger in size, very slushy and good for making snowballs but harder to shovel because of the high amount of moisture.  A wet snow won't accumulate as fast or as much as dry snow because it tends to compact more when it reaches the ground.

The snow for Sunday will likely have snow to liquid ratios around 10:1.  The good news is we're not expecting a total of one inch precipitation to fall.  Right now it only looks like total precipitation will equal between 0.10" and 0.23".  This means our snowfall, assuming it all falls as snow and there isn't a mix or switch over to drizzle sooner, would equal about 1" to 2".  Isolated higher amounts are possible, especially west of here where the snow begins sooner.