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