Saturday, February 8, 2014

Big or Small snowflakes?

With all of the snow we have seen this snow, there is no doubt we have already ran the range of snow types. You know what I am talking about: The type that you can sweep away with a broom, the kind of snow that breaks your back because of how heavy it is and everything in between. You may have asked yourself, 'What makes the snow so different'?

The most logical and correct answer is the temperature of course! But it's not a simple as what you might think. It has more to do with the temperature higher in the atmosphere than at the ground where it falls to. A temperature zone in the atmosphere that we follow closely during winter is called the 'Dendritic Growth Zone (DGZ). Snowflakes grow fastest near 15 Celsius. The DGZ encompasses that 15 degree reading at the temperature zone close to it. The longer the snowflakes are expected to remain in this part of the atmosphere the bigger the snowflake is likely to be. The bigger the snowflake, the faster the accumulation.

You can see why this plays such a big role in our forecasts. A system that may not have very much moisture to work with may be very efficient at making snowflakes and can actually produce higher snowfall accumulations than a bigger/wetter system can!

Here is a graphic to show you what we mean. On the left the DGZ is deeper than on the right, where the zone is smaller and so are the snowflakes!