Wintry weather with snow showers, lightning and 55mph winds could cause power cuts in parts of Scotland on Wednesday, the Met Office has warned.

The forecaster put in place a yellow "be aware" alert for wind to batter northern and western areas in the build-up to Storm Barbara, which is expected to come into effect on Christmas Eve.

Motorists on the A87 Skye Bridge, A9 Kessock Bridge, A92 Tay Road Bridge and A90 Forth Road Bridge have been warned to use caution when crossing on Wednesday due to the high winds hitting the country.

On Wednesday evening, the snow gates on the A93 from Spittal of Glenshee to Braemar were closed in both directions.

Ferry operator CalMac has issued several warnings of disruption to its network as a result of the severe weather, with services involving Oban, Mallaig and Iona among those affected.

Around 37 flights to the Highlands and Islands have either been cancelled or rescheduled by operator Loganair, who said there was "no reasonable prospect" of flights taking off on Friday afternoon and evening.

And around 100 offshore workers may not get home for Christmas due to the weather west of Shetland.

They could be affected because Civil Aviation Authority regulations prohibit flights where sea swells are above six metres.

A BP spokeswoman said: "As we often see this time of year, the weather west of Shetland is becoming increasingly challenging with current sea swells of over six metres and due to rise to over 20 metres at the weekend.

"Unfortunately, this means that we will be unable to carry out our usual crew change flights before Christmas.

"Whilst we appreciate this will be extremely disappointing for those impacted, we are committed to putting the safety of our people above all else."

"Frequent lightning may be an additional hazard across the Northern and Western Isles and the west coast in particular with the potential for disruption to power supplies," the Met Office said.

The wintry blast on Wednesday and Thursday is expected to worsen closer to Christmas Day.

Forecasters have said Storm Barbara will affect the north and north east, as well as parts of the Western Isles and the central belt on Friday into Christmas Eve.

Gusts of up to 90mph are expected, while the Met Office stated structural damage or overhead wire problems in the north of Scotland could occur.

There is expected to be lightning joining snow in the weather mix in some of the affected regions, while travel and ferry services could be disrupted.

Transport minister Humza Yousaf said: "Our National Traffic Control Centre will be operational across the period with our multi-agency response team active on the days leading up to Christmas.

"Ferries are particularly susceptible to disruption due to high winds and we may also see some disruption to flights.

"Those planning to fly or use ferries this festive period should check with their operators for the latest information and consider the forecast as part of their plans."

Mr Yousaf said additional staff and specialist equipment would be brought in to deal with effects on the railways.

He added: "Our operating companies will be out on the network to clear any debris from the trunk roads and to make sure that the risk of any flooding is minimised where possible."