Avalanche Risk Calculator

Safety note: This calculator is an educational, non-authoritative aid. It cannot predict avalanches and must not replace your local avalanche bulletin, professional guidance, or formal training. If you are uncertain, choose more conservative terrain and turn back.

How this avalanche risk calculator produces a relative score

This avalanche risk calculator turns four user-entered condition indicators—slope angle, recent snowfall, temperature trend, and a simplified snowpack stability score—into a relative score and a Low, Moderate, Considerable, or High label. It is intended to make the model’s assumptions visible while you compare them with the local bulletin, recent observations, and the terrain you are considering.

Avalanche-condition inputs and how to estimate them

For an avalanche risk estimate, use observations that describe the particular slope and current snowpack rather than a broad regional average.

• Slope angle (degrees): Slab avalanches commonly release on slopes roughly 30–45°. Measure a representative part of the slope with an inclinometer, phone app, or map tool rather than relying only on its average angle.
• Recent snowfall (cm, last 24–48 hours): New snow can load weak layers and build storm slabs. Use totals from an avalanche center, nearby weather station, or your own measurements. If strong wind accompanied the snowfall, recognize that this simple input may understate loading on lee slopes.
• Temperature trend: Warming can affect bonding, encourage wet-snow problems, and increase the likelihood of natural releases; cooling after warmth can also create crusts and weak interfaces. Select Cooling, Stable, or Warming for the recent trend and the conditions expected during the tour.
• Stability score (1–5): This is a simplified stand-in for snowpack tests and field observations. 1 represents very unstable signs, such as recent avalanches, cracking, whumpfing, or concerning test results. 5 represents comparatively stable observations. When uncertain, do not use a higher rating to compensate for missing information.

Avalanche risk score formula and model inputs

The avalanche score uses direct normalizations of the entered slope angle and snowfall amount. Warming adds to the score, cooling subtracts from it, and a higher stability rating subtracts from it. It does not model a special peak in the 30–45° band; the angle term increases directly with the entered angle.

Risk score:

For this calculator’s avalanche scoring model:

• A = slope angle divided by 45
• S = recent snowfall in centimetres divided by 20
• T = temperature trend: +1 for warming, 0 for stable, and -1 for cooling
• St = the entered stability score from 1 to 5; a higher value reduces the displayed score

Interpreting an avalanche risk score

The avalanche risk output is a relative model result, not a terrain-travel decision or a prediction. A “Low” label does not mean safe snow, and a “High” label is an additional prompt to avoid avalanche terrain and defer to official guidance.

Worked example: avalanche score for a warming 35° slope

Scenario: Consider a 35° slope with 20 cm of new snow during the last 24–48 hours, a warming trend, and an entered stability score of 2.

1. Enter Slope angle = 35.
2. Enter Recent snowfall = 20 cm.
3. Select Temperature trend = Warming.
4. Enter Stability = 2.

How the calculator reads it: The angle factor is 35 ÷ 45, the snowfall factor is 20 ÷ 20, warming contributes 1, and the stability value is 2. The resulting score is approximately 0.61, which this calculator labels Low because it is not greater than 2. That label is not a safety finding: a mid-30s slope, new snow, warming, wind loading, or observed red flags can still warrant a conservative plan and a close reading of the official danger rating and listed avalanche problems.

Avalanche risk model limitations and assumptions

This avalanche score intentionally reduces a complex snowpack and terrain problem to four inputs, so important avalanche information remains outside the calculation.

• Not a forecast: The model does not ingest real-time avalanche bulletins, field reports, or weather-station data.
• Wind loading is not included: Wind can rapidly move snow onto leeward slopes, creating wind slabs even with modest snowfall.
• No aspect or elevation effects: Sun exposure, temperature gradients, and precipitation type vary by aspect and elevation and can change hazard dramatically.
• No persistent weak-layer detection: Deep persistent slabs can be dangerous with little or no new snow and may not be reflected in these inputs.
• Terrain traps are ignored: Gullies, cliffs, trees, and runout zones can turn a small avalanche into a fatal event; this tool addresses only simplified likelihood proxies, not consequences.
• The stability score is subjective: A 1–5 rating cannot replace standardized tests and experienced interpretation.
• Thresholds are simplified: The displayed category cutoffs are part of this educational scoring model, not decision automation.

Recommended avalanche-safety next steps

Before traveling in avalanche terrain, check the local avalanche center bulletin, identify the listed avalanche problems, and plan terrain that matches the conditions and your group’s experience. Carry rescue gear such as a beacon, shovel, and probe when appropriate, and seek training for avalanche travel. Recent avalanches, cracking, whumpfing, and rapid warming deserve priority regardless of this calculator’s score.