The Met Office warned of “significant” transport disruption being likely.
Three days of yellow - “be aware” - severe weather warnings will be in force for most of the country from midnight tonight.
Up to 20cm of snow is possible above 300m in the north and west, and 10cm in the south east of Scotland, with 2-5cm at lower levels.
The agency said winds up to 70mph would hit northern and western Scotland tomorrow, with several centimetres of snow accumulating inland by evening.
A spokeswoman warned: “Travel conditions will start to turn very tricky, resulting in longer travel times.
“Be aware of the potential for disruption to transport due to lying and blowing snow.”
Lightning could also cause power cuts.
On Thursday, ice and hail threaten further problems, and trains could be affected.
In the east, winds could reach 75mph over high ground across Fife, the Lothians and Borders tomorrow.
That will be followed by the risk of snow showers from noon on Thursday to noon on Friday.
Travel disruption is likely to include traffic restrictions on major bridges.
The spokeswoman said: The strongest winds will affect some of the higher-level roads.
“However, the north-westerly winds will also be very strong and gusty at lower levels too, including in areas to the east of high ground.
“A deepening depression will pass northern Scotland on Wednesday, accompanied by strong and gusty winds.
“It will also start to pull in much colder air, which will lead to the showers turning to snow, sleet and hail in many areas later in the day.
“Lightning may accompany the heavier showers, with potential disruption to power supplies.”
Only the southern Borders and eastern Dumfries and Galloway are excluded from the warning areas.
West coast ferry operator CalMac warned of possible disruption because of the strong winds.
Operations director Drew Collier said: “Weather forecasts for across the west of Scotland are predicting a windy and cold run up to the weekend.
“We will review sailings on a case by case basis, but would advise anyone planning to travel by ferry to take this into account when planning journeys in the next few days.”