It's their usual policy, run a heavily delayed schedule unless they have to cancel if the airport closes for example. Now given recent crewing, will they have the resources?
They will only be able to board via front doors for a lot of the day if forecasts are correct and that will cause it's own disruption to punctuality.
But to be fair most flights cancelled are smaller jets, BA canceling all flights from lunchtime is probally a good thing for everybody considering some comments make by crew before!