People travelling are being warned to expect significant disruption after the Met Office upgraded its weather warning to amber with a forecast of heavy snow.
Forecasters warn that some roads may be affected by deep snow, potentially stranding vehicles and passengers, while there is a “good chance” that some rural communities could become cut off.
The warning, valid from 3pm on Wednesday until 10am on Thursday, covers south west Grampian, the southern Highlands, Fife, Tayside, central and southern Scotland.
A yellow warning for snow and ice remains in place for most of mainland Scotland throughout Wednesday and Thursday.
Authorities reminded people that under current coronavirus restrictions they should not be making journeys unless they are for an essential purpose.
The Scottish Government said that specialist snow plans have been activated for key routes, such as the M8, M74, M77 and M80, while new “red X” units have been mobilised to control access to the M80.
Transport Secretary Michael Matheson said: “The Met Office is telling us to expect a period of challenging weather, with an amber warning for snow and most of mainland Scotland facing potential for snowy and icy conditions over the next few days.
“The conditions will likely cause difficult driving conditions and disruption to the wider transport network, so it’s important that anyone that has to make an essential journey during the warning period plans their journey.
“The current Covid restrictions mean you should only be leaving your home for an essential purpose, so please consider if your journey is absolutely necessary before setting off.
“If you do have to make an essential journey, then you should plan your route in advance, drive to the conditions and follow Police Scotland travel advice.
“There may be disruption on other modes of transport, so you should check with your operators before setting off.”
Forecasters said that during Wednesday evening 10-20cm of snow is likely to accumulate above 200 metres with greater amounts at higher elevations.
Amounts at low levels (below 100 metres) are less certain, but 5-10cm is likely in some places by Thursday morning and snow will persist through the morning, slowly dying out during the afternoon.
The Scottish Government said that the Multi-Agency Response Team will be operational for the duration of the weather warnings.
Police Scotland Chief Superintendent Louise Blakelock said: “Government guidance on only travelling if your journey is essential remains in place and so with an Amber warning for snow, please consider if your journey really is essential and whether you can delay it until the weather improves.
“If your journey really is essential, plan ahead and make sure you and your vehicle are suitably prepared by having sufficient fuel and supplies such as warm clothing, food, water and charge in your mobile phone in the event you require assistance.
“The Met Office, Traffic Scotland and SEPA websites and social media channels have valuable information about weather disruptions and we would encourage people to check these sites before setting off on their journey.”