How Ski Patrol Avalanche Mitigation Actually Works

By Travelog Editorial Team ยท Updated August 9, 2026

Before a resort opens each morning, ski patrollers work predawn to deliberately trigger avalanches on steep terrain before skiers arrive, using methods including hand-placed explosive charges, pressurized-nitrogen Avalauncher cannons, and permanently installed remote systems like Gazex (which ignites propane/oxygen gas to create a pressure wave). Alta Ski Area relied on leased US Army 105mm howitzers for this work for 75 years, firing them for the last time in 2023 before transitioning to remote systems.

Long before the first chairlift starts running, a deliberate, explosive operation has often already happened on the mountain above -- work most skiers never witness and rarely think about, despite skiing directly over terrain it made safe that same morning.

The Predawn Routine

This is worth describing precisely, since it's a genuine, scheduled operation, not an occasional emergency response. In the predawn cold, well before skiers and riders line up for the first chair, trained ski patrollers -- in some cases working alongside US Forest Service Snow Rangers -- load explosive charges and deliberately detonate them on steep, high-mountain terrain with a documented history of avalanche activity. The goal is triggering any unstable snow into releasing under controlled conditions, before a skier's own presence could trigger the same slide later that day.

Hand Charges: The Most Precise Method

This is worth naming specifically, since it's the most direct, human-controlled technique. Ski patrollers deploy explosive hand charges while actually skiing through the target terrain themselves, manually placing each charge exactly where it's judged most likely to trigger unstable snow. This is described as the most precise technique available, since a trained human can choose the exact placement point rather than relying on a fixed or remotely-aimed device.

The Avalauncher: A Purpose-Built Cannon

This is worth knowing by name, since it's a specifically designed tool distinct from general military equipment. The Avalauncher is a specialized cannon, originally designed based on a pitching machine, that uses pressurized nitrogen to fire roughly 1-kilogram explosive charges up to a few hundred meters. It's used widely across North American ski resorts specifically because it lets patrol teams trigger avalanches on terrain too dangerous or inaccessible to reach on foot. This tool carries documented risk of its own: in 2014, a Colorado Department of Transportation explosives expert and a Colorado Avalanche Information Center forecaster were both injured during mitigation work on Loveland Pass when an Avalauncher round detonated prematurely inside the barrel.

Military Artillery: Alta's 75-Year History, Ending in 2023

This is worth telling as a specific, recently concluded chapter, since it directly connects ski-resort operations to actual US military hardware. For 75 years, Alta Ski Area in Utah relied on leased US Army 105-millimeter howitzers for its own avalanche mitigation -- artillery pieces, aimed by trained patrollers and staff at historically avalanche-prone terrain, firing 35-pound artillery shells roughly three feet long. In 2023, Alta fired these howitzers for the last time, concluding a documented 75-year military-artillery legacy at that specific resort. At the program's broader peak, roughly 40 surplus 105mm howitzers were deployed across nine ski resorts and seven state transportation departments combined, used for both ski-area and highway avalanche mitigation.

The Shift to Remote, Permanent Systems

This is worth explaining as the current direction the industry has moved toward, replacing the artillery-based approach above. Remote Avalanche Control Systems (RACS) are permanently installed towers or structures that hold explosives or trigger mechanisms, detonated remotely rather than requiring a patroller to physically aim and fire each shot. The Gazex system, in use at resorts including Alta, Brighton, Jackson Hole, and Taos (with MND, the manufacturer, having installed nearly 200 units across the US), works by remotely releasing oxygen and propane gas into a network of pipes installed directly in known avalanche start zones -- when the gas mixture reaches a specific concentration, a remote firing mechanism ignites it, creating a downward-facing pressure wave that triggers the slide, all without anyone needing to physically enter the terrain. Wyssen Towers, a different system (installed by Utah's transportation department starting in 2016), instead drop physical explosive charges from an elevated tower structure onto the target terrain below.

Why This Matters for What "Patrolled" Actually Means

This is the practical connection worth making to this pillar's companion page on off-piste versus patrolled terrain. The predawn mitigation work described above is precisely what "patrolled" terrain actually means in practice -- an active, ongoing safety process, not simply terrain that happens to be inside a resort's boundary. Terrain outside that boundary receives none of this mitigation work, which is the specific, concrete reason off-piste and backcountry snow carries genuinely higher, uncontrolled avalanche risk even when it sits immediately adjacent to patrolled runs.

What This Means for Understanding Resort Safety

The practical takeaway is that a resort's in-bounds terrain being open for skiing is itself the result of deliberate, professional mitigation work completed that same morning -- not an assumption that the terrain was simply always safe. Knowing the methods behind that work (hand charges, Avalaunchers, remote systems like Gazex) is worth carrying into an honest understanding of exactly where that safety work stops -- precisely at the resort's own boundary rope.