article: More than 100 schools have been closed. The Northern Ireland Ambulance Service (NIAS) said it was "experiencing difficulty in responding to some emergency calls" due to the weather. "We would ask that people only call 999 in a real emergency and to remain patient if there is a delay in ambulance response," the NIAS said. It said NIAS staff would "continue to prioritise calls on the basis of clinical need". A number of Translink Metro bus services were also affected on Thursday due to the snow. The Upper Hightown Road in Belfast has been closed because of poor road conditions. Police patrols in the area appealed to the public to avoid the road and obey the cordon and diversion signs. The Met Office said a yellow warning of snow and ice will remain in place until 11:00 GMT on Friday. Parents of pupils at Loughash primary school, Dunamanagh, County Tyrone, are advised that the school will be closed on Friday. Transport NI, formerly known as Roads Service, said that strong winds are also likely to combine with the snow to make conditions more difficult. It said salting and ploughing operations are continuing. Police have advised drivers to slow down, put their lights on, leave more room to stop than usual and brake gently to avoid skidding. "Drive slowly on snow in the highest gear possible," a PSNI statement said. "Do not assume your vehicle can handle all conditions. Even four-wheel drive vehicles can encounter trouble on winter roads," it added. Places in the south east of Northern Ireland that do not have much snow will still be bitterly cold and will be at risk of ice, forecasters have said. The cold weather will continue throughout Thursday and it will remain very cold until the beginning of next week. Check out the latest travel news for Northern Ireland For the latest on the roads visit the BBC's travel news page and keep up-to-date with the latest updates on BBC News NI's Live pages. Alternatively, for regular travel bulletins listen live to BBC Radio Ulster and follow @BBCNITravel. Below are a number of other traffic information sources. Trafficwatch NII Transport NI Translink @PSNITraffic
summary: Snow showers are continuing to affect the road network across Northern Ireland on Thursday and there is also the risk of ice on roads.