Item: MARCH MEGA THAW: FORECASTING CASE STUDY DURING A PROLONGED EARLY SPRING HEAT EVENT IN UTAH, 2025–26
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Title: MARCH MEGA THAW: FORECASTING CASE STUDY DURING A PROLONGED EARLY SPRING HEAT EVENT IN UTAH, 2025–26
Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026
Authors:
- Nikki Champion [ Utah Avalanche Center, Salt Lake City, UT, USA ]
- Jenna Malone [ Alta Ski Area, Alta, UT, USA ]
- Jonathan Morgan [ Alta Ski Area, Alta, UT, USA ]
Date: 2026-09-28
Abstract: The 2025–26 winter in Utah produced a complex snowpack shaped by persistent weak layers, multiple rain-on-snow events, extended high-pressure periods, and record low snowfall. Persistent slab was a forecasted avalanche problem for over one hundred consecutive days, from December 2, 2025 to March 14, 2026. Entering mid-March, the snowpack still held intact persistent weak layers, while surface conditions varied widely by elevation and aspect. From March 14–30, Utah experienced a prolonged period of record or near-record warmth. Salt Lake City reached 27°C (80°F) on March 19, the earliest reading in recorded history, and set a new March record high of 27°C (81°F). Few mountain locations saw a meaningful overnight refreeze during this period. As free water moved deeper into the snowpack, avalanche danger oscillated repeatedly between MODERATE and CONSIDERABLE, with wet loose, wet slab, and glide avalanches as the primary concerns. Forecasters faced elevated uncertainty about the timing, distribution, and destructive potential of wet slab releases, particularly in terrain containing older persistent weak layers. This case study examines the meteorological setup of this historic heat event, the avalanche cycle that followed, and the differences between public and operational forecasting perspectives during this complex, prolonged wet cycle. Unlike prior short-lived warming events, the sustained nature of this period reduced the reliability of standard assumptions such as overnight refreezes and predictable daily stability trends, requiring continual reassessment of danger ratings, travel advice, and public messaging. This event illustrates how prolonged warm periods can rapidly shift avalanche problems and challenge traditional spring forecasting frameworks in intermountain and continental snow climates.
Object ID: ISSW2026_P4.47.pdf
DOI: https://doi.org/10.15788/1790099376
Language of Article: English
Presenter(s): Nikki Champion
Keywords: wet slab avalanches, persistent weak layers, spring warming event, avalanche forecasting, snow climatology, Utah
Page Number(s): 2115 - 2122
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