Amber "be prepared" warnings for snow have been issued by the Met Office for many parts of Scotland, including the Highlands and western isles, Strathclyde, the south west, Lothian and Borders and Central, Tayside and Fife.
Snow could fall in these areas between 5pm today and 9am tomorrow, with some heavy showers and blizzard conditions predicted.
A yellow "be aware" alert for high winds in many regions including Orkney and Shetland, the Highlands and Strathclyde is also in place.
The Met Office forecasted 10 to 20cm of snow on higher-level routes, with conditions in the mountains described as "atrocious".
Exposed areas on the west coast are also likely to see unusually high sea and swell conditions, it said.
Julian Mayes, a forecaster with MeteoGroup, the weather division of the Press Association, said: "It's going to be windy throughout the day, with the highest wind speeds on the west coast.
"There will be maximum gusts of 60 to 70mph at any time today and this evening."
Waves off the west coast have already reached heights of around 20 metres (65ft). Researchers recording waves off the north west coast of the Isle of Lewis said average peaks measured between 13 and 14 metres (42-45ft) during the day.
A number of sensors in the sea monitor wave frequency and direction all year round as part of the Hebridean Marine Energy Futures project based at Lews Castle College in Stornoway.
Arne Vogler, senior research engineer, said: "It gives us a very good understanding of what is going on out there and today I have to say it is pretty horrendous.
"During the winter we would see five or six metre (16-19ft) waves, that is quite normal. Then we get your every day gale and they would go up to seven or eight (22-26ft).
"But today we have strong westerly winds, with gusts up to hurricane force and waves of 20 metres, with an individual wave of 21.8 metres (72ft) at around 11.30am."
Scottish Transport Minister Keith Brown said: "Looking at the latest Met Office forecast for frequent and at times heavy snow combined with gales force winds will mean a testing journey for many this evening and also, crucially, during rush-hour tomorrow.
"We would expect to see difficult conditions emerging on our roads, as well as the potential for disruption to all modes of transport.
"As always we are playing our part by delivering winter service treatments to our roads, but sudden weather changes can occur, and the impact the weather can have from one location to the next can be very varied.
"Our Multi-Agency Response Team (MART) will be operational ahead of and during the expected weather conditions. The Scottish Government's resilience team is also monitoring conditions to ensure a co-ordinated response.
"I would again ask the public to stay up to date with live travel information and local radio reports. They can also access the Traffic Scotland website, internet radio bulletins and Variable Message Signs which are being used to provide up to date information as the situation develops."
Many ferry services faced disruption throughout the morning, with cancellations in the Western Isles, including the Oban to Lochboisdale sailing.
Ferries to Orkney and Shetland were also affected, with some cancellations and delays.
The strong winds forced the closure of the Forth Road Bridge, the Erskine Bridge, Clackmannanshire Bridge and Skye Bridge to high vehicles.
Storm-force gales brought gusts of 84mph to the Western Isles last week, bringing road and school closures as well as causing damage to some homes.
ScottishPower produced record amounts of electricity at its 28 windfarms, with more than 135 gigawatt hours produced between January 25 and 31, enough to power 1.6 million homes in an average week.