Warning of heavy snow and ice for Scotland
Heavy snow, blizzards and treacherous conditions are expected to cause disruption across Scotland.
The Met Office issued an amber warning for snow in the Highlands, Grampian, Central, Tayside, Strathclyde and Fife from 09:00 on Saturday.
There is also an amber warning for ice covering much of Scotland and northern parts of England from 10:00 on Saturday to 06:00 on Sunday.
Drivers are being warned about the risk of rare "freezing rain".
The Met Office said that normally warnings for ice indicated slow formation over a number of hours, but Saturday's ice will come from freezing rain which can see ice forming instantly on contact with surfaces.
Black ice may affect bus, train and air travel and dangerous driving conditions are likely to lead to road crashes, road closures and longer journey times.
The snow is expected to cause some vehicles and passengers to be stranded and delays and cancellations to rail travel are likely.
Forecasters said 5-10cm (2-4in) was likely to fall widely in the warning zone, with some areas seeing 20cm (8in), and perhaps as much as 40cm (16in) over higher ground. The amber warning is in place until 08:00 on Sunday.
The snow will clear from the west by Sunday morning.
The areas affected by the amber warning for ice are Central, Tayside and Fife, Strathclyde, south west Scotland, Lothian and Borders, north east England, north west England, Yorkshire and Humberside, East Midlands and West Midlands.
BBC Scotland weather presenter Kirsteen MacDonald said: "An area of low pressure, moving in from the Atlantic tomorrow, is expected to bring disruptive, wintry weather.
"As rain bands associated with the area of low pressure run into cold air, a mixture of snow and freezing rain is expected.
"As heavy, freezing rain moves in during Saturday morning, it'll lead to rapid formation of ice. Treacherous conditions are expected on roads and pavements."
She added: "The ice and snow bring the risk of public transport disruption and very difficult conditions on the roads and pavements. Strong to gale force south easterly winds will also lead to drifting and blizzards over high ground. The public are advised to be prepared."
Temperatures will range between 0C and 2C.
The Scottish government's resilience division Ready Scotland tweeted that "very dangerous" travelling conditions were likely.
A Met Office yellow warning for wind is also in place for the Northern Isles and Caithness between 12:00 on Saturday and 06:00 on Sunday. Winds are likely to gust up to 60-65mph.
Heavy rain and gales will affect parts of Northern Ireland and south western areas of the UK on Saturday.
The wettest areas could see 30 to 50mm of rain (one to two inches) in six to 12 hours, while winds could gust to between 50 and 60 mph, especially in exposed coastal areas.
The wintry weather is expected to ease off during Sunday morning.