A large, wet avalanche that officials say was easily big enough to destroy wood frame houses or a railroad car occurred in Tuckerman Ravine on Mount Washington last Friday.
According to officials at the Mount Washington Avalanche Center, last week’s rain created dangerous conditions in the ravine. Rain saturated the thick snowpack that had developed from the 144 inches of total summit snowfall to date this winter.
By Friday night, more than 2 inches of rain had fallen on the summit with temperatures in the 40s and nearing 50 lower on the mountain at Hermit Lake.
Sometime on Friday the 12th, a large, wet slab avalanche occurred in the Headwall area of Tuckerman Ravine on a ski run and forecast area known as the Lip.
The avalanche forecast for the day warned that, “wet slab avalanches may slide naturally without a human trigger today”, as well as, “the floor of Tuckerman Ravine is particularly threatened by a natural avalanche from the Headwall area.”
Officials at the avalanche center said that after inspecting the site, it was likely that the firm snowpack, weakened by rain, burst like a dam as water pressure built up in the stream channel beneath.
The avalanche measured 160 feet across the 12- to 20-foot crown and ran 2,000 feet with a vertical fall of 500 feet.
By the avalanche size and destructive potential scales, this avalanche is classified as R3D3.5 or medium relative to path. Officials say an avalanche that size is capable of easily destroying wood frame houses or a railroad car.