Category Archives: Alps snowfall

Collapse of the Weisshorn glacier in 1819

Two hundred years ago this December a huge part of the Weisshorn glacier in Switzerland crashed down several thousand feet to the valley below.

saas fee glacier
A glacier above the village of Saas Grund, Switzerland. Viewed from below I am always struck by how precarious they look.

At 6am on December 27th 1819 the villagers of Randa, near Zermatt, were awoken as millions of tonnes of snow and ice swept away boulders, rocks, gravel and mature larch trees. Though the debris missed the village the force of the slide created a blast of air that moved entire buildings and their contents, burying 12 people, all but two of whom escaped with their lives.

Eyewitnesses described the noise of the falling mass as the loudest thunder and said a bright flash accompanied the slide before darkness once again enveloped the village.

First light revealed the utter devastation of the avalanche that have covered an area of pasture 2,400ft by 1,000ft by 150ft high.

It was not the first avalanche to bring disaster to Randa. In 1636 the village was destroyed by a similar avalanche when 36 people were killed. It is said that that occasion saw a much greater chunk of the flacier fall from the slopes of the mountain, at 14,783ft the 5th highest in the Alps.

Two other less serious falls happened in 1736 and 1786 but not precisely in the same place. This time only a small part of the glacier fell down.

Could a similar disaster happen again? With climate change and the nature of the Alps being constantly on the move it is possible. Earlier this month it was reported that part of a glacier on the Mont Blanc Massif, just 40 miles away as the crow flies, was on the brink of collapse.

I don’t have local figures but a look at the recent climatology in London shows that anomalies during the past couple of years – warmer than average summers and low rainfall – have been similar to what happened in 1819.

summer mean

summer rainfall

Of course the difference between now and 1819 is that we have early warning systems in place that can help prevent loss of human life in the event of a catastrophic avalanche.

The Weisshorn in the far distance seen from the slopes above Grächen

The climatology of Zermatt

Zermatt and the surrounding Valais area in Switzerland has a varied Alpine climate. But a study of weather data back to the beginning of 2011 reveals distinct seasonal patterns in terms of air pressure and precipitation.

Although these patterns can’t be relied on completely in terms of planning a wintersport or summer climbing trip awareness of the extremes can be a big help. Knowing when pressure is usually highest can help mountaineers pick that ideal week in summer to tackle 4,000m peaks. Similarly pinpointing weeks with lowest pressure and highest precipitation is the holy grail for those hunting for powder snow.

Looking at the averages pressure is highest on December 23rd. Further scrutiny of rolling weekly averages shows this date coincides with the week commencing December 20th. Anyone who’s been to the Alps at Christmas time will know that this period can be very unreliable for deep snow cover. In terms of summer pressure is highest on August 21st.

Pressure is lowest on February 2nd. Again this date often coincides when the deepest snowfalls often arrive after weeks of dry weather. Despite the unsettled pattern at this time annual precipitation is usually greatest at the end of October / beginning of November. I’ve lost count of the number of times the press interpret these early snowfalls to be a sign of a bumper season ahead only for the skies to clear at the end of November and, sometimes, the arrival of unseasonably warm weather.

The second wettest period is usually the end of April / beginning of May. Again, this past week has seen some parts of the Alps record the best snowfalls this season.

zermatt pressure

zermatt rainfall

An erratic season for snow in the Alps

Earlier this winter there were many reports on how good snowfall had been in Austria. But on closer inspection it was clear that the weather pattern at that time only favoured certain resorts.

In contrast with last year the totals I’ve used in my cross section of the range don’t look that exciting; Bourg-St-Maurice, the jumping off point for Savoie resorts including Les Arcs and Val d’Isere, has recorded 96mm of precipitation this season, in stark contrast to the 433mm it recorded last season between Christmas Day and February 5th.

In Switzerland Arosa, a resort well placed to pick up snow from any direction, has recorded the same this season as last. Totals in Davos are well down on last season. Similarly San Bernardino has recorded about half the amount of precipitation than it did last season. Its location toward the southern side of the range has been sheltered from the prevailing winds this year. That said it did enjoy a big dump last week.

Going further south and east St Vallentin in Italy has recorded about a third what it did at this stage last season.

Mean temperatures overall are about 2C to 3C lower than they were last season.

snowmap update
30-day precipitation totals reveal that Bourg St Maurice recorded just 96mm, compared with last year’s 433mm while Obertauern in the east recorded 77mm, compared with 106mm the same period last year


Galtür avalanche 20 years on

With all the snow falling in Austria I noticed that next month is the 20th anniversary of the Galtür avalanche that left 31 dead, 26 injured and left a trail of devastation.

This animation shows its devastating power.

The avalanche was considered the worst in 40 years. Three weather systems originating from the Atlantic accounted for large snowfalls up to 4m deep. Freeze-thaw conditions created a weak layer on top of an existing snowpack; further snow then settled. This, together with high wind speeds, created large drifts and caused roughly 170,000 tons of snow to be deposited.

Even more snow is expected in this and surrounding regions.


The extreme amounts will fall mostly on the north of the range with very little on the south side, more or less the opposite of what happened last year.

Of course Alpine snowfall, from year to year, has always varied greatly as this study of San Bernadino shows.



Winter sports and Alpine snowfall variability

The Alpine snowfall season finished just below average in the Splügen area of the Swiss Alps. Abnormally warm weather after decent snowfalls in February and March curtailed the season; mean temperatures finished over a degree warmer than average between November and April.

The figures make depressing reading for anyone who enjoys winter sports and come after a study suggested that bare Alpine slopes could become a much more common sight in the future.

I first visited this area of the Alps in 1981, returning most February half-terms, apart from 1989 when the snows failed to arrive until after Easter. The season that hastened the installation of artificial snowmaking in resorts across Europe has always left me wondering just how much snowfall has varied.

Using San Bernardino, a village at 1636m in the southwest of Grisons canton, I had a look at temperature and rainfall data back to 1999 to see what patterns were present. The figures confirm that some years see metres fall while others have barely enough to cover the pistes.Screen Shot 2017-05-17 at 13.20.29


Temperatures, meanwhile, show a general upward tick from 2005-06.

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While the above graphs show typical variability they don’t reveal much about month to month conditions.

Closer scrutiny of the data shows that early season dumps of over 30cm, the kind that really get the snow bases going and keep the earth below chilled for a long season, are becoming rarer. Indeed, apart from a blip in 2013/14 there have been no big early season dumps since 2009/10. The seasons are taking much longer to get going.

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As the second graph shows big dumps of snow are happening later in the season. If there is not already a decent snow base these snowfalls can thaw much faster because spring sunshine has already warmed the ground.

Another way of trying to find how the climate has changed is to look at how many ‘ice days’ there were in a given period – ice days are when the maximum temperature reaches -0.1C or lower over 24hrs.

The graph below shows the past three years have been fairly constant though this season’s total of 83 is 37 days fewer than the highest total in the series, 2005-06 which clocked up 119 days.

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I’ve visited many resorts in the Alps which, obviously, will be affected differently by the changing climate – the range of microclimates in the Alps is staggering.

In conclusion, considering the data and my experience, I’d say that though the Alps have definitely warmed the variability and ebb and flow of the climate means it is impossible to say with confidence that by the end of this century the slopes won’t be covered in the white stuff.

I chose San Bernardino because it is fairly central in the entire Alpine range and is also the most local SYNOP station I can find to the Valtellina range that I have been visiting most years since 1981. Any climatologists reading this would point out that my data range does not stretch back the necessary 30 years to make a judgment on the stats. If anyone can point me to a site that offers data back to 1980 I would happily update my figures and graphs.

My trip this year to Madesimo, 8 miles as the crow flies from San Bernardino, was timed just right for a dump of snow in February that followed weeks of dry weather.

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Temperature inversions were seen in February (above). Snow was only deep enough to descend Madesimo’s Canelone run, reached by the Groppera lift to 3,000m once February snows had arrived

The area has enjoyed some epic snowfalls over the years including 2013/14 when many found themselves snowed-in following a 2m dump of snow.  The first of many snowfalls during what was an epic season.

Here is a timelapse of the huge 2m snowfall in Madesimo over Yuletide 2013