Melting Away the Snow

It was just last week residents of northern Illinois and southern Wisconsin were digging out of nearly a foot snow, but this past weekend the snow was quick to melt.  The combination of heavy rain, and thunderstorms, along with a quickly melting snow pack caused quite a bit of runoff and standing water in fields, ditches and backyards.  Rises in the creeks and rivers were also noted with Flood Advisories issued for the Rock River at Byron and Dixon, as well as for the Kishwaukee River at Belvidere.  While significant flooding is not expected, the rivers along those points have reached 'Action Stage' meaning the water will begin flooding some of the low lying areas around the river.  No additional rainfall, or significant snow, is expected this week but the river will continue to run high and could very well remain high through Winter.

The heavy rain had an impact on the snow this weekend but there are other processes that cause snow to melt away, and quickly in some cases.  The first is through warming temperatures and the sun.  The warmer the temperature rises above freezing the more the snow melts away.  The next two processes, probably not known as well, are through sublimation and latent heat release.

Sublimation is the process of which a solid goes directly into the gas phase, without turning into a liquid.  This usually occurs when the air temperature is below freezing and there is a strong wind blowing over the top layer of snow.  You can't see the process take place in real life, but rather notice the snow beginning to dwindle.  The third process, and usually the most efficient and quickest, is through latent heat release. 

Have there been times in the winter when we get really foggy you've noticed the snow quickly melting?  The higher moisture in the atmosphere leads to condensation (often times fog in the winter) and condensation releases latent heat.  When water - either in the solid, liquid or gas phase, moves from a lower to a higher ordered state, the air surrounding the water will have energy added to it.  When ice (snow) melts, energy is being taken from the environment and absorbed into the ice (snow) to loosen the hydrogen bonds that are holding it together.