Motorists are facing "very challenging" conditions in parts of the country after heavy snow showers throughout the night.

Commuters have been warned of possible disruption with warnings of drifting snow and blizzards.

Forecasters said more than 5cm (2in) could accumulate at lower levels this morning, with more than 6in (15cm) on high ground.

An amber "be prepared" weather warning is in place until 11am with strong and gusty winds forecast to lead to snow drifts and blizzard conditions at times.

Police in the Highlands said roads were passable with care, while in the Grampian region motorists have been advised to drive with caution.

The weather brought isolated power cuts to communities in the north of the country last night and a number of roads were hit by accidents, with the southbound lane of the A9 closed for a period near Dalwhinnie because of a jack-knifed lorry.

Traffic on the M8 and other main motorways was also slowed due to heavy snow while the Kessock Bridge was closed to high-sided vehicles.

The amber warning covers most regions apart from Orkney and Shetland, where a yellow warning for snow is in place.

BEAR Scotland, which manages and maintains the trunk roads in the north east and north west, advised people to take precautions before setting out.

Eddie Ross, BEAR Scotland's North West Operating Company Representative, said: ''The North West, parts of the North East and the M80 have experienced heavy snow showers throughout the night, at all levels on most routes.

"Our winter teams have been working throughout the night and all routes in the North West and North East are open, although conditions remain very challenging. Our teams are continuing to patrol and treat routes as necessary to help manage the adverse conditions. This will continue throughout the next 24 hours as the winter weather is forecast to continue.

"We encourage motorists to prepare well for their journeys and drive with care whilst these winter conditions continue.''

Transport Minister Derek Mackay said authorities were well prepared for the weather.

He told BBC Radio Scotland: "The road network is flowing fairly well, maybe a bit slower but still flowing.

"I think we've prepared very well for the weather and the snow with 180 plus gritters out we've worked hard to prepare the roads for these conditions."

He added: "Through this snow period we'll be fully operational. The 180 gritters have been out treating the roads, it will vary between 150 and 180 and that's just our operating companies for the trunk roads. Local authorities I'm sure will be doing their work as well in addition to that but the teams working on preparedness and treating roads will continue through this weather warning until the amber passes at around 11am, but will stay fully operational until that need passes."

Forecasters predict that the cold snap will continue into next week.

Matthew Martin, a forecaster with MeteoGroup, said: "Thursday evening and Friday will be slightly less cold, then there will be a colder Arctic flow on Saturday bringing snow which will be generally restricted to coastal areas, and remaining very cold into early next week."

Police Scotland have issued travel advice to motorists.

Chief Inspector Louise Blakelock said: "There is a risk of localised disruption to travel likely and we would ask motorists to take precautions before they set off.

"If you are travelling, you should ensure that you and your vehicle are adequately prepared for the conditions.

"Make sure you have sufficient fuel and supplies such as warm clothing, food and water in the event you are delayed for several hours.

"Charge your mobile phone and plan your route, as well as alternative routes.

"Road policing crews will be patrolling the road network to keep people safe during this period - please follow our advice to travel with extra caution."

More than 40 schools in Dumfries and Galloway are shut, as are some in the Borders and South Lanarkshire have been closed, while 29 schools and nurseries are shut in the Highlands.

A missing woman was found unconscious following a three-hour search in blizzard conditions yesterday.

Tweed Valley Mountain Rescue Team (MRT) was called out at 5pm on Wednesday to help in the search for a missing woman in the Innerleithen area.

Rescue 177, a Royal Navy Sea King Helicopter from HMS Gannet, was scrambled and used its Infrared camera to assist in the search.

Three-year-old search dog Rauour and handler John Romanes of the mountain rescue team were also involved.

Three hours into the search Rauour found the casualty, who was unconscious, about 30ft off a forest track.

She was airlifted to hospital.

Tweed Vallet MRT Deputy Team Leader Dave Wright said: "As well as being a committed member of Tweed Valley MRT, John undertakes a vast amount of additional SARDA (Search and Rescue Dog Association) training with Rauour.

"It goes without saying that this training has paid off when we are able to locate a casualty quickly and ensure that they receive the appropriate medical care."

"The conditions were pretty bad with strong winds and driving snow - it's a safe to say that the combined efforts of John and Rauour, Tweed Valley MRT, Police and the Royal Navy saved the woman's life."