This true-color image captured by the NOAA/NASA Suomi NPP satellite’s Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on January 10, 2017, shows the extent of the storm system that dropped several inches of snow over portions of Oregon and Washington and resulted in school closures, downed trees, and the loss of power to thousands of area residents. According to the Seattle Times, some neighborhoods in Portland received more than 1 foot of snow.
Although true-color images like this may look like photographs, they aren’t. True-color imagery is created by combining VIIRS’s color channels that are sensitive to the red, green and blue (or RGB) wavelengths of light. In addition, several other channels are often also included to cancel out atmospheric interference, such as clouds and aerosols, which can cause a blurry picture. RGB composites are used in a wide variety of applications, including the monitoring of severe weather, differentiating snow/ice and ash/smoke from cloud, or even the boundaries between warm and cold air masses.
Link to full article: https://www.nnvl.noaa.gov/MediaDetail2.php?MediaID=1988&MediaTypeID=1