The chill will make temperatures feel sub-zero, and ice may appear on untreated surfaces.
It tweeted: "Snow is forecast for tomorrow so we ask motorists to please drive to the conditions". Cloudier than recent days, with some snow possible in the south.
GETTY / REUTERS / @UKsnow_updates Where will it snow? "There is a good chance that some rural communities could become cut off".
The storm has moved in the direction of Scandinavia, drawing cold air from the north sea.
Wolves' clash with Sunderland is in doubt as snow warnings across the United Kingdom force late pitch inspections for this weekend.
There could still be upwards of 20cm (8in) of snow to come in exposed areas.
John West, Met Office meteorologist, said: "We saw a fairly consistent stream of snow showers overnight, and there will be a constant feed throughout the day and into Friday".
Caledonian MacBrayne ferry services between Tarbert and Lochranza, Oban and Tiree via Coll and Ullapool and Stornoway were cancelled for the rest of the day while many other routes are facing disruption.
Photographer's 'soul-crushing' video of starving polar bear goes viral
He rummages inside a a nearby trash can used seasonally by Inuit fishers, finds nothing and resignedly collapses back down onto the ground.
Forecasting maps show that between three and five inches could fall in Wales and the West Midlands over the weekend.
Forecasters had earlier warned of a danger to life, with gusts of up to 90mph possible in northern parts of Scotland.
The Met Office says Storm Caroline's winds are now confined to the far north-east of mainland Scotland and the Northern Isles, and there could be gusts of 70-80 miles per hour at times, especially over Shetland, on Friday.
Heaviest snow showers will be confined to northeast Scotland as Saturday draws to a close.
An amber (second highest) weather warning is in place between 6am and 11.55pm for Highlands and Eilean Siar, Orkney and Shetland and Grampian, where winds of 60-70mph are expected widely.
The site adds that between 2cm and 5cm of snow is likely across most of the country, with 10cm to 20cm expected in parts of north Wales and Scotland.
"Road, rail and air travel delays are likely, as well as stranding of vehicles and public transport cancellations".