Both peaks were 52.4 GW, with a "trough" of 51.7 GW at 1830.
Furthermore, demand was almost flat for a full twenty minutes from 1730 to 1750
Why am I telling you this geeky fact?
It looks as though the reason for this is demand response kicking in.
Industrial users anticipate high "Triad" charges which can occur without warning on days of very high peak demand in February .