Global Forecast System (GFS)

The Global Forecast System (GFS) is a National Centers for Environmental Prediction (NCEP) weather forecast model that uses a set of mathematical equations to simulate the behavior of the Earth's atmosphere. The GFS couples four separate models (atmosphere, ocean model, land/soil model, and sea ice) and runs four times a day, and produces forecasts up to 16 days in advance. 

For more info about the GFS, please visit: www.ncei.noaa.gov/products/weather-climate-models/global-forecast