ScotRail is to urge people to go home now as it plans to start shutting down the network from 2pm.
It said there would be no trains in the red warning area around the Central Belt either tonight or tomorrow morning.
The closure is expected to cover lines across the Central Belt and other parts of Lothian and the Borders and Strathclyde, and in Fife and Tayside.
• READ MORE: Red alert over Fife Snow
A spokesperson said: "Travel home now. We will be closing the railway - it will be run down from 2pm.
"We are looking at what services can run, but a red warning means a risk to life.
"It's looking horrendous and snowing heavily in places."
The decision follows the train operator cancelling more than 200 services across eastern Scotland and around Glasgow in advance of the snowfall.
The operator has since cancelled more trains in Glasgow, including many at Glasgow Central.
The ScotRail Alliance with track owner Network Rail said yesterday that sets of points, which enable trains to switch between tracks, would be set in one direction to reduce the potential for them to stop working from ice and snow.
This has been standard practice fro several years.
It said: "This will allow us to position staff at critical locations, where they can help keep points and signalling equipment clear of ice and snow.
"On a normal day, our points move regularly to allow different trains to travel on different routes.
"When we are faced with snow and ice, this can increase the risk of a points failure – snow and ice can get caught between the points, which causes delays."