The NASA GEOS-5 atmospheric data assimilation system uses millions of observations every six hours to compile a global forecast picture. Using a combination of satellite imagery of the past few days and a simulation of future outgoing longwave radiation emitted from the earth's surface (and subsequently blocked by clouds), this video was produced showing the evolution of the winter storm now affecting the US eastern seaboard. The weather produced by our atmosphere when it balances incoming solar

WINTER STORM: Seattle is seeing its biggest snowstorm in years as millions across the Midwest through the Mid-Atlantic states gear up for another wintry blast of their own. Rob Marciano reports. https://abcn.ws/2SjmUGP | ABC World News Tonight with David Muir