Yet another bout of snow, sleet and ice recently affected much of the Tennessee and Ohio Valley regions. Although clouds were clearing in western portions of this region, allowing for a broad scale satellite view of the newly laid snow/ice field, eastern portions remained cloud-covered until sunset. While ground reports contain valuable information about the depth of snow and/or ice, they’re only point measurements, so assumptions often have to be made about the spatial extent of the snow, until satellite observations are available (unless clouds obscure). So, those observations would have to wait until the next day, during visible sunlight hours…or would they? Well, not exactly…which is the point of this blog post.
The image below (Image 1) is a Snow/Cloud RGB produced by SPoRT and disseminated to collaborative NWS field offices. The green colors represent the background surface (grass, trees, cities, etc.), while the deeper reds represent snow/ice cover. White colors depict clouds, while reddish-white represents very cold clouds containing ice crystal clouds. Notice the swath of snow that is visible from NE Texas into the Midwest. Meanwhile, clouds obscure any snow/ice in eastern areas.
Clouds had pushed eastward by sunset, but did still not move far enough to provide a clear indication of the eastward extent of the snow/ice field that had just fallen. However, once the VIIRS Day-Night Band imagery became available later that night, the spatial extent of the snow and ice could be fairly easily observed. Notice in the next image (Image 2) the snow and ice cover that was apparent over portions of the Tennessee and Ohio Valley region.
This type of imagery can be helpful for operational forecasters when trying to assess the potential societal impacts of lingering snow and ice, and also the impacts on sensible parameters such as temperatures and relative humidity, which can help improve weather forecasts.