A +NAO, -AO means the Atlantic continues to drive systems east across thee UK but cold air entrainment and building cold over Scandinavia will meet over the UK.

This keeps us on the cool side of average pretty much right through next week with an ongoing snow threat, primarily but not exclusively over the hills of Scotland, N Ireland and N England and Wales.

500mb height anomaly shows bitter cold air spilling out of the Davis Straits into the mid latitude flow.

Then building Scandinavia cold seeping towards England beneath a toppling high in over Scotland.

The GFS 850mb temp charts show cold air pushing in over the UK from both Atlantic and Scandinavia this weekend. Note the shrinkage of mild air with each incoming system. Also the very cold air seeping sw from Scandinavia underneath the high toppling in over the UK.