A case study and comparison of mid-winter warming and solar driven wet slab avalanche cycles

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Abstract

Wet slab avalanches are poorly understood and often difficult to forecast. Yet, wet slab avalanches can be destructive and may become more common in a changing climate. As the onset of wet avalanches moves earlier in the winter season due to climate change, understanding snowpack and meteorological characteristics of wet slab avalanches will become increasingly important. In this study, we examined two recent late-January wet slab cycles triggered by warming and solar input in the Rocky Mountains of Idaho and Montana, United States. We posed two questions to help us understand these potentially increasingly frequent, mid-winter wet slab cycles: i) what are the weather and snowpack patterns of two mid-winter wet slab cycles and ii) how did these non-rain-on-snow, mid-winter warming events compare to the historical climate normal? In both locations, a short-lived ridge of high pressure strengthened over the region from late January to early February 2024. Temperatures rapidly increased to 6° C at middle and upper-elevation locations and remained above freezing for 48 to 72 hours. Wet slab avalanches (Montana: n=68, Idaho: n=11) released on a layer of facets resting on a crust formed in late December and slab depths averaged 40 to 150 cm. Avalanches primarily occurred on southeast, south, and southwest aspects at middle and upper elevations. Additionally, positive January monthly temperature trends exist in both locations from 1990 to 2020, and these two cycles from 2024 highlight impacts of midwinter warming events with unstable snowpack conditions. These cycles also highlight how a relatively uncommon mid-winter warming event with low radiative input can produce very large destructive wet slab avalanches. Understanding mid-winter warming events and associated wet slab avalanche cycles will help us prepare and forecast for potentially more common scenarios like this in the future. 

Suggested Citation

Peitzsch, E.H., Johnson, C., Savage, S., Miller, Z., and Hoppinen, Z., 2024, A case study and comparison of mid-winter warming and solar driven wet slab avalanche cycles, in Proceedings: International Snow Science Workshop 2024, Tromsø, Norway, p. 620-628.

Study Area

Publication type Conference Paper
Publication Subtype Conference Paper
Title A case study and comparison of mid-winter warming and solar driven wet slab avalanche cycles
Year Published 2024
Language English
Publisher Montana State University
Contributing office(s) Northern Rocky Mountain Science Center
Description 9 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
First page 620
Last page 628
Country United States
State Idaho, Montana
Additional publication details