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.
There’s been countless reports about amazing amounts of snow falling across the French, Swiss and Italian Alps to the point where some agencies have been proclaiming that it has been the best season for the white stuff in 30 years.
Extraordinary totals have fallen in some areas. Bourg-St-Maurice, the jumping off point for Savoie resorts including Les Arcs and Val d’Isere, has recorded over 400mm of precipitation over the past 30 days, equating to around 4m of snow at the resort summits.
In Switzerland, large amounts of snow in a short period caused chaos in Zermatt, stranding tourists after the area’s rail services suffered disruption.
Away from the north and west side of the Alps, however, snowfall, while good, has been less impressive the further south and east you look.
It is a far cry from last year where some resorts on the southern side of the range were particularly dry. San Bernardino, during the last 30-days, has recorded 179mm of precipitation. During the same period last year just 14.6mm fell!
The outlook for the Alps continues to look unsettled with snow forecast to fall at resorts that are in deficit to the Valais and Savoie areas.