It’s not surprising that the high cloud has spread south so rapidly in the last few hours as there was a 150 knot northerly jet at midnight down across the country.
I don’t know the exact technical term for this ‘shield’ of cloud is, other than calling it jet stream cirrus but I know its a harbinger of rapid development. I quite like shield of cloud that I’ve coined, who knows perhaps it’ll catch on.
November 10 visible satellite image
The jetstream in action