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.
What this avalanche risk calculator does
Avalanche hazard is shaped by terrain, recent weather, and the current structure of the snowpack. This tool combines four commonly discussed inputs—slope angle, recent snowfall, temperature trend, and a simple snowpack stability score—to create a relative risk score and a matching category (Low/Moderate/Considerable/High). The intent is to help you think systematically about conditions and identify when the combination of factors should trigger extra caution and more reliance on official forecasts.
Inputs (and how to estimate them)
- Slope angle (degrees): Most slab avalanches release most frequently on slopes roughly 30–45°. Measure with an inclinometer/phone app, a map tool, or by assessing a representative section of the slope you plan to travel on (not just the average angle).
- Recent snowfall (cm, last 24–48 hours): New snow can overload weak layers and create storm slabs. Use totals from an avalanche center, nearby weather station, or your own measurements. If snowfall came with strong wind, treat risk as potentially higher than this simple input captures.
- Temperature trend: Warming can reduce bonding, promote wet snow problems, and increase the chance of natural releases; rapid cooling after warm periods can also create crusts/weak layers. Choose Cooling, Stable, or Warming based on the last day or two and what’s happening during your tour.
- Stability score (1–5): A simplified stand-in for snowpack tests and observations. 1 = very unstable (recent avalanches, obvious cracking/whumpfing, poor test results). 5 = very stable (no red flags, strong bonding, supportive snow). When in doubt, choose a lower number.
Formula and scoring model
The calculator uses a lightweight weighted score. Slope angle is first normalized so that low-angle terrain contributes less and prime avalanche angles contribute more. Temperature trend is treated as a small adjustment. Stability reduces the score.
Risk score (conceptual):
Where:
- A = normalized slope-angle factor (higher in the 30–45° range, lower below ~25°)
- S = recent snowfall factor (more new snow increases load)
- T = temperature trend factor (+1 warming, 0 stable, -1 cooling)
- St = stability score (1–5; higher stability reduces risk)
Interpreting results
The output is best treated as a relative indicator rather than a prediction. A “Low” result does not mean “safe,” and a “High” result should be interpreted as a strong prompt to avoid avalanche terrain and defer to official guidance.
| Risk category | Score range | Practical interpretation (non-prescriptive) |
|---|---|---|
| Low | < 2 | Fewer contributing factors are present; still check forecast, watch for red flags, and manage terrain exposure. |
| Moderate | 2–4 | Some ingredients for instability are present; be cautious with steepness, slope features, and group management. |
| Considerable | 4–6 | Multiple factors align; conditions may support human-triggered avalanches—treat this as a strong warning signal. |
| High | > 6 | Many risk factors present; avoid avalanche terrain and rely on official bulletins and conservative decisions. |
Worked example
Scenario: You are considering a slope around 35°. The area received 20 cm of snow in the last 24–48 hours. Temperatures are warming through the day. Your observations suggest only moderate stability (you choose Stability = 2).
- Enter Slope angle = 35.
- Enter Recent snowfall = 20 cm.
- Select Temperature trend = Warming.
- Enter Stability = 2.
How to read the output: A mid-30s slope sits in a common release-angle band, 20 cm of new snow adds load, and warming can further reduce bonding—so you should expect the score to land in a higher category than the same slope with no new snow and cooling temperatures. Use that signal to cross-check the official danger rating and problem types (storm slab, wind slab, persistent weak layer, wet snow, etc.) and to adjust your terrain plan.
Limitations & assumptions (important)
- 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/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 ignored: Gullies, cliffs, trees, and runout zones can turn a small avalanche into a fatal event; this tool only addresses likelihood proxies, not consequences.
- Stability score is subjective: A 1–5 rating cannot replace standardized tests and experienced interpretation.
- Thresholds are simplified: The category cutoffs are heuristic and intended for education and consistent thinking, not decision automation.
Recommended next steps
Always check your local avalanche center bulletin before traveling, carry rescue gear (beacon/shovel/probe) when appropriate, and get training if you plan to travel in avalanche terrain. If you observe recent avalanches, cracking, whumpfing, or rapid warming, treat those as high-priority warning signs regardless of the calculator score.
Snowpack Sentinel Patrol
Turn the calculator’s risk score into a feel-for-the-snow session. Balance mitigation and patrol timing while storms and temperature swings reshape the slope’s stability curve. Keep the stress meter calm to stack points, and vent slabs before they roar to life.
Drag the mitigation slider on the left edge or use W/S (↑/↓) keys to tune snowpack relief. Tap anywhere or press Space/Enter to deploy a control blast when the charge meter glows.
Tip: The calculator’s risk score seeds base stress. Warm spells and rapid loading spike it quickly—steady mitigation keeps you ahead of the curve.