Maybe the Mods will append this to the Southeast weather waiver thread. FlightAware shows 1/7/17 was not a good day for Delta, for Delta Connection carriers, or anybody flying to/thru ATL, RDU, JFK/LGA/EWR...
That kind of weather event could lead to 100,000+ passenger rebookings across the DL system on a single day. Use the app when you can.