Scotland's weather: Amber warning of snow from Storm Doris
Travel disruption and power cuts are expected across the east of the Central Belt and southern Scotland, south from Edinburgh tomorrow.
The amber - "be prepared" - warning from 2am to 6pm upgrades a previous yellow - "be aware" - alert, which remains in force for other mainland areas as far north as Aberdeenshire and the southern Highlands.
Storm Doris has also triggered an amber warning for 80mph winds across the northern Midlands in England and north Wales tomorrow.
Separate warnings for gales in the far north and heavy rain in the far south of Scotland today, and across the west coast on Saturday, have also been issued.
A Met Office spokesman said: "Heavy snow is expected on Thursday.
"Accumulations of 10 to 15cm are likely quite widely, with 20 to 30cm falling on hills above 300 metres.
"This will lead to disruption to transport and perhaps power supplies.
"As Storm Doris moves eastwards across central parts of the UK on Thursday a spell of heavy snow is expected on its northern flank.
"There is some uncertainty over the track of Doris and therefore over the extent of snowfall, but confidence is now higher for disruptive snow to affect the amber area."
For the yellow warning area, the spokesman said: "Snow accumulations of 5 to 10cm are expected on some hills with 2 to 5cm possible to lower levels to the north of the Central Lowlands.
"In addition, strong winds are expected to develop with gusts of 50 to 60 mph.
"This will result in drifting of the snow and blizzard conditions over high ground.
"Associated heavy rain at lower levels will be an additional hazard.
"The combination of snow, strong winds and heavy rain is likely to lead to disruption to transport networks and perhaps power supplies."
The amber warning for England includes gusts of up to 80 mph, which the Met Office warned could damage buildings, and cause power cuts and and widespread travel disruption, with a danger of injury from flying debris.
A separate yellow warning for severe gales gusting to 80mph has been issued for Orkney, southern Shetland, the north coast of the mainland and the north-east tip of Aberdeenshire until 3pm today.
The ScotRail Alliance with Network Rail has cancelled several trains today north of Ardgay or Lairg on the Far North Line between Inverness and Wick/Thurso "due to forecasted severe weather".
Flights, ferries and road travel could also be disrupted.
The Met Office said: "West to northwesterly severe gales are expected for a time on Wednesday, bringing gusts of 65-70 mph and locally 75-80 mph over parts of the Northern Isles.
"A swathe of very strong winds is expected to affect Orkney, southern parts of Shetland and the far north of mainland Scotland early on Wednesday, easing from the west through the morning.
"These will however briefly clip the far north east of Aberdeenshire around the middle of the day."
A further yellow warning for heavy rain that could cause flooding has also been issued for southern Dumfries and Galloway from 9pm today to 2pm tomorrow.
Up to 40mm of rain is expected to fall, with snow over some higher ground.
A yellow warning for heavy rain has also been issued for the Highlands and west coast for Saturday.
Up to 75mm is forecast between midnight and 9pm, which the Met Office could disrupt travel and cause flooding.