Cold fronts will generally start from areas of low pressure and follow the trough of low pressure south and to the west of the low. WebCorp
A trough of low pressure extended northwards across the Bay of Biscay, bringing the cloud and rain that occurred over Brittany. WebCorp
We are, unfortunately, in a stable weather pattern with a large trough of low pressure in the middle levels of the atmosphere parked directly overhead. WebCorp