- Hundreds of car drivers are stuck on the M80. Police Scotland say they are not allowing any more traffic on to the carriageway.
- Planes remain grounded at Glasgow Airport with about 600 passengers stranded in the terminal.
- The majority of schools in Scotland - some 1,600 - will stay closed on Thursday.
- The Red weather warning - the highest to be issued by the Met office - will be in force until 10:00 on Thursday
- Rail and bus services will be disrupted while the blizzard conditions continue.
- The Met Office has issued a red warning for snow for parts of central Scotland
- The extreme weather warning runs from 15:00 on Wednesday until 10:00 on Thursday.
- People are being advised not to travel in the worst affected areas unless absolutely necessary
- Most schools in Scotland are closed on Wednesday and Thursday
- Glasgow Airport is closed and buses and trains in the red warning area have stopped
An Emirates flight from Dubai has landed at Glasgow Prestwick after being diverted from Glasgow International. There will be no flights from Glasgow International for the rest of Wednesday. The Emirates flight landed at 19:08, after a flight of more than seven hours.
At Edinburgh and Glasgow airports, all Flybe and Stobart Air flights have been cancelled until 12:00 tomorrow. Passengers have been advised not to travel to the airport.
In Aberdeen, Flybe have cancelled flights until 10:00 tomorrow and customers have been told not to go to the airport.
One of those stuck on the M80 is Michael Blair, who has been near Cumbernauld for four hours.
He told BBC Reporting Scotland he stopped for fuel at Old Inns at about 2.30pm and has moved less than a mile in the four hours since.
Mr Blair, who is trying to get to Perthshire, said: "We have no idea how long we are going to be here."
Motorists have already been stuck in the snow on the M80 for several hours.
Laura McLachlan told BBC Radio Scotland's Newsdrive programme that her journey home from work in St Andrews normally takes an hour and a half.
But she has spent more than five hours in her car, since setting off at 12:00, and has been sitting at the Castlecary junction for some time.Copyright: PA
She said there were vehicles parked on the carriageway "as far as the eye can see" and the majority of them were HGVs.
"It baffles me because in this kind of weather, these are the first things that should be off the road," she said.
"Because the majority of issues that are being caused, are being caused by HGVs."
Stein Connelly, of Transport Scotland, told BBC Radio Scotland's Newsdrive programme that a "managed closure" was put in place on the A720 Ediburgh bypass in a bid to get gritters to the front.
He said: "We've got one lane open there. The weather radar is showing that this might get short break for maybe an hour so we'll continue with the gritters there so hopefully we can get it clear and moving over the next hour and get most people moving and on their way."
He added that HGVs were continuing to experience traction problems on the M80 and the M8.
Mr Connelly said: "We've brought in specialist equipment, we're working with Police Scotland, going the opposite way down the carriageway.
"We're actually connecting on to some of these HGVs and pulling them out. So as soon as we can get these vehicles going, we will.
"It's very, very difficult, it's challenging driving conditions especially on the M8 and the M80 just now. It's blizzard snow conditions and it's dropping temperatures. But we're going to continue with it - we've got all our fleet out there, we'll continue gritting and ploughing right through the night and we'll just need to work as hard as we can."
Several hundred travellers are stuck at Glasgow airport after a number of flights were cancelled.
A shortage of hotel accommodation nearby means many of them may have to spend the night in the airport.
Its operations manager, Mark Johnston, said it had been a challenging day and there were about 600 people in the airport this evening.
He said they were in discussions with the Red Cross about bringing camp beds into airport and they were trying to book conference rooms on the ground floor of the nearby Holiday Inn.
- Copyright: BBC
Speaking on BBC Radio Scotland's Newsdrive programme, Humza Yousaf raised concerns that some motorists had not taken heed of the Scottish government's advice to make only essential journeys.
He said: "Looking at the extensive number of cameras, there seems to me a lot of people choosing to travel and we have to question whether all of that is necessary.
"Clearly for some people, it will absolutely be - for emergency workers, those in the care sector and so on and so forth - that would be essential travel.
"But I do have to question whether all of it is essential. It's important to say that this travel advice has not only been since the red warning but for last couple of days since we've known about the amber warning, we've been telling people that they should avoid all travel and I would reiterate that message."
He said motorists should avoid all but essential travel in the worst affected areas of Scotland until 18:00 on Thursday, when the Met Office amber warning is lifted.
Chief Superintendent Stewart Carle, Police Scotland's head of road policing, spoke to Mhairi Stuart on BBC Radio Scotland's Newsdrive progamme, from a road collision on the M80 southbound at the M876.
He said traffic was at a standstill but a tractor plough was trying to get lorries moving. An ambulance was trying to make progress on the hard shoulder.
"We've had a number of incidents involving minor collisions, that's then slowed the traffic, it's caused a build up of traffic jams and then the ploughs and gritters can't get in to do their work," he said. .Copyright: PA
He added that he hoped to avoid having people stuck in their cars for lengthy periods
"I'm concerned about that," he said. "I remember back in 2010 we had people stuck overnight and we're very mindful of that.
"We're hoping to get the traffic moving again with ploughs and tows. We may have to stack HGVS on to lane one and the hard shoulder at some point to allow lane two to be opened up to motor vehicles but we're not at that point yet."
He said he believed a lot of the drivers caught in the traffic jams had heeded the warnings to leave work early to beat the snow but "they've just been caught out by it".
This image from the satellite receiving station was prepared at 13:01 this afternoon.
The UK is mostly cloud covered as expected but snow is visible in some areas and between broken clouds, e.g. Kent and East Sussex, and across parts of Northern England and the Highlands.
The University of Dundee said: "We have provided a larger area than just the UK & Ireland as the image clearly shows the cloud patterns across the North Sea associated with the cold air flow from the East which is bringing the cold weather."
Social media reports that you will not be covered by insurance if you drive during a red warning are untrue, according to insurers.
However, they advised drivers to heed warnings.
Malcolm Tarling, from the Association of British Insurers, said: "We would urge all drivers to pay close attention to advice from local authorities and the emergency services in areas affected by snow – particularly where there is a red warning.
"People’s safety is paramount.
"However social media claims that motor insurance will be invalid if people drive during a red warning are not true.
"Motor insurance will cover you in the usual way, providing you are driving within the law.”
The subway in Glasgow will stop running at 7pm. A spokeswoman said the operators needed to take into account the safety of staff. It is hoped that the subway will be opened as usual at 6.30am tomorrow.
BBC Scotland correspondent in the Scottish Borders
It's pretty bad here. I've just driven down the A68 from a place called Carfraemill to Lauder and I couldn't believe the conditions. It was absolutely white out, the road was completely white, completely covered, hard-packed snow down there.
I had driven that road about an hour before that, heading north, and it was completely black. This is the problem they've had all day - these pulsing snow showers coming in, whiting out the road and not having enough drivers to get the salt working or enough gritters to get up and down the road. It's just been a constant battle all day.
Already the schools are off tomorrow - Scottish Borders Council made that call very early.
They cancelled them for today yesterday afternoon - that's one of the reasons there hasn't been too much disruption across the Borders, that call was made nice and early. The roads were very quiet. We were out and about at rush hour this morning and it made a huge difference.
Ironically though, that does mean you don't have that traffic flow across the road to get that grit working to clear the roads. I suspect there's going to be a lot more problems on the roads in the Borders tonight and tomorrow.
Temporary beds and bedding from the Red Cross have been delivered to Glasgow Airport for passengers who will be stranded overnight.
A spokesman for the airport said staff were doing all they could to get people back home. However, he added that some travellers would have to stay at the airport while snow blizzards sweep the central belt of Scotland.
There will be no further flights in or out of the airport today. A review of tomorrow's schedule will be made later