Mount Washington in New Hampshire is best known for Tuckerman’s Ravine, a steep open bowl that holds snow into July. On March 29th the southeast slope of the Mount Washington summit cone experienced the largest recorded avalanche.
U.S.F.S. Snow Ranger Chris Joosen commented that: “A slide of this magnitude has never been recorded on this particular slope.”
This portion of the mountain rarely experiences large slab avalanches activity outside of storm cycles. The weather leading up to this event had been clear and warm, with avalanche forecasts calling for wet slide activity later in the afternoon. This slide was the largest ever recorded on this face. The crown was 3ft deep and the slide and ran 650ft horizontally and 385ft vertically. The avalanche was estimated to be a D3 slide. The other unusual part of this slide was the absence of any indication of warm temperatures or water playing a role in the avalanche.
The USFS Mount Washington Avalanche Center issues forecasts for the region, but not the summit cone where the avalanche occurred. The summit cone is considered less prone to avalanches than the steeper and wind-loaded gullies of Tuckerman and Huntington Ravines. The slope of the Southeast face of the summit cone is approximately 45 degrees.
It is suspected that the slide was human triggered. The slide was thought to have been triggered when a weak layer of facets beneath an ice lens collapsed, triggering the overlaying hard slab. 20 people were on the slope when this avalanche occurred and it is incredibly fortunate that nobody was caught or injured in the slide.