Weather conditions deteriorated further in the North last night, and the Met Office predicted grim conditions for the rest of the week, following the heaviest snow falls for almost 20 years.
Derry, Omagh and the Newry by-pass were badly affected and there were lengthy traffic tailbacks late last night on the main between Dundalk and Newry. The N2 at Aughnacloy on the Border between Monaghan and Co Tyrone was impassable.
Parts of Co Fermanagh were also severely affected by Arctic winds, freezing fog and plummeting temperatures that accompanied the "most significant snow event" since January 1982.
All flights into and out of Northern Ireland's three main airports were delayed indefinitely yesterday evening. Bus services to and from Derry were limited and ferry times were brought forward as weather conditions worsened.
Many rural routes were described as "extremely treacherous" and were closed throughout the day, with some main roads becoming impassable as the night wore on.
Police were last night continuing to advise motorists not to travel unless their journey was absolutely necessary.
Snow began to fall steadily in Belfast from lunchtime yesterday. Mr Colin Donnelly of the Belfast Weather Centre predicted the city would remain under a substantial covering of snow for the rest of the week.
"The ground is cold enough and the air is cold enough for it to lie, and the overnight temperatures aren't going to rise above freezing," he said.
A spokeswoman for AA Roadwatch blamed the cold snap on a cold front streaming down from the Arctic Circle.
