With 850 temps that low over the north sea anywere down the east coast of britain would be at risk of deep snow, there would be regional differences due to the covective nature of the showers, But i would urge caution a cold spell is now in the bag but as cold as the ecm gfs are showing has a few hurdles to cross yet but i would go for 60/40 in favour of severe cold if the UKMO joins the party(by the way the UKMO is still a belting run just not on the same level as the other big 2) on the 0z tommorow then that would go up to 70/30. Anyway just enjoy these charts as they are incredible