This looks to me as if it may be the start of an anvil forming which I ‘think’ is when the cloud rises up in the form of an anvil. I think it is a sign of stormy weather, you never know up in the dales.

It almost looks like this was taken from an aeroplane but being high(ish) up in the hills and a long(ish) focal length of 190mm gave the effect.

The start of an anvil?