Item: ASSESSING PUBLIC BACKCOUNTRY AVALANCHE FORECASTS
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Title: ASSESSING PUBLIC BACKCOUNTRY AVALANCHE FORECASTS
Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026
Authors:
- Ethan Davis [ Sawtooth Avalanche Center, Ketchum, ID, USA ]
- Zachary Miller [ Sawtooth Avalanche Center, Ketchum, ID, USA ]
- Scott Savage [ Sawtooth Avalanche Center, Ketchum, ID, USA ]
- Dallas Glass [ Northwest Avalanche Center, Seattle, WA, USA ]
- Spencer Logan [ Colorado Avalanche Information Center, Boulder, CO, USA ]
- Ethan Greene [ Colorado Avalanche Information Center, Boulder, CO, USA ]
- Blase Reardon [ Flathead Avalanche Center, Hungry Horse, MT, USA ]
- Christine Donnelly [ Flathead Avalanche Center, Hungry Horse, MT, USA ]
- Andrew Schauer [ Chugach National Forest Avalanche Center, Girdwood, AK, USA ]
Date: 2026-09-28
Abstract: Avalanche danger ratings are the cornerstone of a public backcountry avalanche forecast, and the "Tier 1" danger — the highest rating across all elevation bands — is its most significant and far-reaching component. This project investigates Tier 1 danger ratings at five North American avalanche centers via forecast assessments conducted from 2019 through 2026, using two approaches: one within 24–72 hours of the forecast date and one in the off-season, both leveraging additional observed avalanche and weather information. We ask how often Tier 1 danger changes during assessment and what factors drive those changes. Previous studies found that assessed Tier 1 danger differed from forecast Tier 1 danger in 16–25% of forecasts (Techel and Schweizer, 2017; Statham et al., 2018b; Logan and Greene, 2023; Donnelly and Reardon, 2024); across 15,576 forecast-zone-days, our data show a 15.8% equal-weighted change rate, with center-level rates spanning 3.4% to 32.2%. Among changed ratings, 73% were overforecast and 27% underforecast, and almost all moved by a single danger level. Change rates rise steadily with forecast danger and fall with forecaster confidence. Storm Slab and Wet Loose problems are the most volatile. Day 2 Tier 1 ratings change 1.7–4.2 times as often as Day 1 forecasts. Danger level, forecaster confidence, and avalanche problem type predict revision across centers. Forecast assessment can identify recurring sources of mismatch and guide improvements in Tier 1 consistency within a program, but each center's rate reflects its own assessment design as much as its forecasting, so comparing programs will require a shared protocol.
Object ID: ISSW2026_P2.30.pdf
DOI: https://doi.org/10.15788/1790098965
Language of Article: English
Presenter(s): Ethan Davis
Keywords: regional avalanche forecasting, forecast verification, forecast assessment, avalanche danger, forecaster confidence
Page Number(s): 1251 - 1258
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