I am scheduled to fly to London tomorrow on BA in CW with a connecting ET flight onto Munich on Saturday afternoon. The LHR-MUC flight is on a seperate PNR because it was booked after the JFK-LHR return.

Unfortunately it looks like there may be significant weather related delays tomorrow due to a snow storm that is about to hit the area. What's my best way of ensuring I get to my final destination and minimal extra cost. Is there anyway to combine the PNRs or will BA cut me some slack because both flights are BA?