The Department for Infrastructure has advised that some roads which would normally be cleared as part of the scheduled salted network remain impassable because of snow drifts.
A DfI spokesperson said: “Salting and ploughing of the scheduled network has been ongoing through the night. In the North and West of the province the scheduled network is all passable with care.
“However large parts of Counties Down and Armagh and the southern part of County Antrim experienced further significant accumulations of snow through the night.
“The more significant challenge in these areas though has been the drifting of snow that even when roads are cleared very quickly the wind is causing the snow to blow back across the carriageway.
“The M1 has both lanes cleared in both directions whilst the A1 dual carriageway has a single lane clear in both directions.
“Many of the roads in these areas that would normally be cleared as part of the scheduled salted network are not passable this morning.”
The A Class roads that are not passable at 0545 include A25 Belleek to Newtownhamilton and A29 Newtownhamilton to Keady. There are large snow drifts to the side of the A50 Katesbridge to Moneyslane, A25 Rathfriland to Newry, A26 Moira to Nutts Corner and A49 Ballynchinch Road but these are all passable at present although the situation can change quite quickly.”
Flights to and from Northern Ireland are also experiencing disruption.
Belfast City Airport said: “While Belfast City Airport remains fully operational, the adverse weather on the UK mainland has caused delays and cancellations this morning.
“Flights to and from London Heathrow, Edinburgh, Glasgow and Cardiff are among those cancelled.
“It is essential that passengers check with their airline before travelling to the airport today.”