Austria was also badly affected as the snowfall was followed by an unexpected thaw, triggering at least one avalanche and the threat of more, forcing authorities to close the St Gotthard tunnel, a key north-south route through the Alps.
Last night, more than 500 lorries were backed up at its entrance and some 500 nearby homes were evacuated in an attempt to avert a loss of life similar to that earlier this month in France, when an avalanche hit hamlets near Chamonix.
The Swiss authorities said that more than a metre of snow had fallen in the past two days and a similar fall had blanketed the Austrian Tirol. They said the situation was reaching danger levels, with mountain barriers designed to prevent avalanches now full and unable to hold back any more snow.
The situation was described as "extremely critical" in the Bernese Oberland, which had about 1.5m of snow. About 20,000 tourists were trapped in the popular resorts of Adelboden and Grindelwald. "The atmosphere is good," said the Grindelwald tourism director, Joe Luggen. "People are enjoying themselves."
In western Switzerland, rescue services sent search dogs and equipment to the resort of Villars after a huge avalanche crashed down on a ski slope.
The slope had been cordoned off for safety reasons but it was not clear whether people had ignored warnings and if there were any casualties. About 2,000 people were without electricity in the Austrian Tirol.
Princess Caroline of Monaco and Queen Beatrix of the Netherlands were among tourists trapped in the resort of Lech am Arlberg, according to an Austrian news agency.
Many Austrian communities were isolated by the weather and there was chaos on many roads.
The Swiss Defence Minister, Adolf Ogi, called in the air force to help deliver supplies to isolated communities and aid evacuations. Hundreds of people had to leave their homes on Thursday because of the risk of avalanches.
A snow slide crashed on to railway lines outside the southern Swiss town of Zermatt on Thursday, damaging power cables. The resort was without electricity for most of the night and temporarily cut off by road and rail.
In Britain, climbers and hill walkers were warned of likely avalanches in the Scottish mountains this weekend.
The Scottish Avalanche Information Services, based at the National Outdoor Training Centre, at Glenmore Lodge, near Aviemore, said "avalanches will occur" on the popular 3,700ft Creag Meagaidh, near Laggan, Inverness-shire. Forecasters rated hazards as "high".