There is a Power Station on the Welsh side of the Dee Estuary. The day was cold and very still.
The large cloud produced by the Power Station exhaust shows up as a single white pixel on this NOAA 17 image.
11th December 2008.
NOAA 17/18 Data via EUMETCast 2008. Processed with David Taylor's AVHRR Manager and HRPT Reader.
And Below is an image of Connah's Quay Power Station Plume taken from the North West by Robert Moore on 3rd January 2009.
There is evidence of the quite heavy industry around Deeside.