Global Forecast System. The operational numerical weather forecasting model run by NCEP. The GFS superceded the AVN and MRF models, on which it is largely based. Forecast data from the GFS is available out to 180 hours at full resolution and 16 days at a reduced resolution.
07:26 EDT About one-third of the country is expected to be hit by a heatwave over Christmas, with temperatures likely to reach 40 degrees Celsius or more.