Two camps of models this morning- those that see a strong major warming happening Dec 25-26, and those with a weaker #SSW (or in the case of GFS, no reversal at all) by Dec 29th. Still uncertainty in how this will unfold 7-10 days out. pic.twitter.com/HnpDsVtgKO

— Dr. Amy H Butler (@DrAHButler) December 19, 2018