Europe Records 146 Avalanche Deaths as Persistent Weak Layer Drives Dangerous Season

Europe's Avalanche Season Claims 146 Lives in Pattern of Persistent Instability

The 2025-26 European ski season ended with 146 avalanche deaths across the Alps, Apennines, Pyrenees, and Scandinavian Mountains - more than double the 70 fatalities recorded the previous winter. The primary culprit wasn't extraordinary snowfall or massive storm cycles, but rather a persistent weak base layer that formed early in the season and refused to stabilise for months.

Whilst some media outlets labelled this a record season, the statistical reality is more nuanced. The 20-year average for European avalanche deaths sits at 104.35, with a standard deviation of 35.64 - meaning seasonal variability between 69 and 140 deaths falls within normal statistical range. This season's toll exceeded that range only marginally. The winter of 2009-10 remains the actual outlier, with 194 deaths across Europe.

The Structural Problem That Defined the Season

What distinguished this season wasn't a single catastrophic event but a pattern avalanche forecasters recognise all too well. Thin, inconsistent snowfall across much of the Alps during late November and December created a deeply buried persistent weak layer - what German-speaking forecasters call "Altschneeproblem" (old snow problem). This fragile layer, typically composed of faceted snow crystals, can persist for months and proves notoriously difficult to stabilise.

The danger remained relatively contained through early winter, with fatalities staying low through December. But beneath the surface, conditions were deteriorating. When significant fresh snow finally arrived after a prolonged dry period in mid-January, it loaded slopes rapidly whilst placing stress on that buried weak layer.

Three Months of Elevated Danger

The first major spike came in calendar week 3 of 2026 (12-18 January), with 18 deaths - the beginning of what would become the season's defining pattern. Fresh snowfall and strong winds repeatedly added new snow and wind-drifted slabs on top of the unstable base throughout late January and February. The snowpack never properly adjusted. Instead, each storm effectively reset the danger, creating what the SLF describes as an "avalanche window" - a period when conditions remain primed for large, destructive slides.

February proved deadliest, recording 52 deaths across the month. Calendar week 8 (16-22 February) alone claimed 21 lives - the highest weekly toll of the season. The first week of February saw 15 deaths, with another 16 spread across the month's remaining weeks.

This prolonged instability is characteristic of seasons dominated by persistent weak layers. Unlike storm snow instabilities that often stabilise within days, these deeper structural problems can linger for weeks or months. Even experienced backcountry users found themselves caught off guard, particularly when surface conditions appeared stable.

The Spring Transition

By early March, fatalities dropped sharply as the snowpack slowly adjusted and storm intensity decreased. The nature of avalanche risk shifted toward wet snow avalanches driven by warming temperatures and solar radiation. These are generally more predictable than deep slab avalanches, though still dangerous. Melt water saturating snow layers encountered the persistent weak base layer, triggering several size 3-4 avalanches as spring progressed.

What the Season Reveals About Avalanche Risk

The 2025-26 season ranks as Europe's worst avalanche winter in the last decade, though not the worst in two decades. It underscores a critical reality: the most dangerous winters aren't necessarily the snowiest or stormiest. Sometimes the greatest risk builds quietly, layer by layer, long before major storms arrive.

The persistent weak layer structure this season proved more sensitive and longer-lasting than many experienced backcountry users anticipated. Familiarity with terrain and conditions can create a false sense of security - a lesson reinforced throughout this winter. When structural instability exists deep in the snowpack, even moderate new snow loads can trigger large, destructive avalanches.

For anyone planning backcountry travel in European mountains, this season serves as a reminder that early-season snowpack development matters as much as mid-winter storm cycles. A weak foundation established in November can dictate conditions through February and beyond, regardless of how much snow falls later. Understanding snowpack structure - not just surface conditions - remains essential for managing risk in avalanche terrain.