DISCUSSION: As this latest ice storm continues to deliver notable impacts to many sections of the Central United States, many are wondering how an icing event actually comes into play during a given winter storm. For instance, what makes an icing event unique from other winter storms which typically only have rain, sleet, and snow involved during the majority of a Winter-time low pressure system's life-cycle. The graphic attached above visually depicts the various scenarios from a horizontal and vertical standpoint for why various types of precipitation occur during winter storms around the world. Note how in this graphic, it is the exact depth of the cold air from the surface on up which dictates whether the precipitation remains frozen, freezes then melts and then re-freezes, freezes before melting and then re-freezing near or right at the surface, or melts and does not re-freeze again.
Attached below is a solid explanation on this current ice storm scenario courtesy of forecasters over at the National Weather Service office located in Sioux Falls, South Dakota: "Why all the freezing rain heading into northwest Iowa and adjacent locations tonight and Monday, and already occurring in the central and southern plains? We have a deep layer of air warmer than freezing above the surface. Meanwhile the surface temperatures are below freezing. As snow falls from the top of the cloud, it warms in the layer which is above freezing producing rain, then refreezes near the surface or at the surface as ice. That is what causes freezing rain."
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©2017 Meteorologist Jordan Rabinowitz