I would not expect a claim here to be successful. In other areas BA loses EC261 when general or knock-on events happen, due to the "all reasonable measures" aspect of EC261. But in this case that specific service simply cannot operate and it's by no means certain that a A319 would get through either. Plus by any measure the area has had pretty exceptional weather for the last few weeks. I may be wrong about that, and I wouldn't want anyone to be dissuaded from going to court or CEDR with their claim, but that's my expectation. There are some events where BA is not responsible - that's not in doubt - and then you have to consider whether that would apply here.