Standard MODIS visible imagery makes it very difficult to discern between low cloud cover and snowy ground. One tool disseminated by SPoRT to its National Weather Service (NWS) partners is a MODIS false color image product, which highlights differences in the spectral signatures of snow and clouds to produce a color-enhanced image that makes it easy to discern the difference between snow on the ground under clear skies and clouds.
A large winter storm brought snowfall to the Upper Midwest and Northeast during the week of Christmas 2012. A MODIS visible image from the Terra overpass earlier today (top image below; 1658 UTC on 28 December 2012) shows how difficult it can be to determine which regions are cloudy and which regions are clear but with snow cover. However, in the MODIS false color composite (bottom image below; 1658 UTC on 28 December 2012), regions of clear skies with snow cover appear as bright red and regions with clouds appear as white. In the image, the southern extent of the snow on the ground in the Midwest is easily identified to be as far south as the Texas panhandle. Unfortunately, a second storm system is covering much of the Eastern third of the U.S.; however, there are a few clear patches that show snow on the ground over Ohio and Northwestern Kentucky.
Forecasters at the NWS use these images 1) to determine the extent of snow cover in remote, less-populated regions where reports are hard to obtain and 2) to differentiate between snow cover in clear skies and low clouds or fog, which are important for airports and drivers.