Avalanche Weather Forecasting

• Introduction
  • Glory Bowl Avalanche Incident
  • Avalanche Impacts
  • Avalanche Weather Forecasts
  • About the Module
• Basic Avalanche Information
  • Introduction
  • Avalanche Climate
  • Types of Avalanches
  • Avalanche Paths
  • Avalanche Terrain
  • Avalanche Triggers
  • Avalanche Sizes
  • Avalanche Development
  • Sliding Surfaces
  • Stable vs. Unstable Snowpacks
  • Snow Bonding
• Avalanche Weather Forecast Process
  • Overview
    • The Forecast Process
    • Forecasting Guide and Data Form
  • Pre-forecast Preparation
    • Overview
    • Avalanche Climate
    • Avalanche Terrain
    • Weather History
    • Recent Avalanches
  • Current Weather
    • Overview
    • Precipitation
    • Wind
    • Temperature
    • Cloud Cover & Solar Radiation
  • Future Weather
    • Overview
    • Precipitation
    • Wind
    • Temperature
    • Cloud Cover & Solar Radiation
  • Making the Avalanche Weather Forecast
• Forecast Exercises
  • Introduction
  • Case 1
  • Case 2
  • Case 3
  • Case 4
  • Case 5
• Summary and Resources
  • Summary
  • Resources

The Forecast Process

The sequence of weather events throughout the winter season determines whether a snowpack is prone to avalanching. Careful monitoring of the types of weather that lead to the development of slab, weak, and sliding layers is paramount in forecasting avalanche weather. This is accomplished by continually evaluating the main weather parameters in your forecast area. These include precipitation, wind, temperature, and cloud cover.

The next four sections of the module outline a process for forecasting avalanche weather, the goals of which are to determine if:

• Critical thresholds for the weather parameters are being met or exceeded
• The potential for avalanches is increasing, decreasing, or staying the same based on the current and forecasted weather

The steps in the process include:

• Pre-forecast preparation, where you gather basic information about your area, such as its climate, terrain, snowpack, and weather history
• Assessing current weather, where you evaluate the weather over the last 24 hours or so
• Forecasting future weather, where you make a weather forecast for the important avalanche weather parameters
• Making the avalanche weather forecast, where you evaluate the impact of the current and forecasted weather on your area’s avalanche potential and determine if it is increasing, decreasing, or remaining the same

Before we get started, note the following:

• Since an avalanche weather forecaster cannot do a good job without some knowledge of terrain and snowpack, we will include information about those topics when appropriate; for more information on snowpack, see the COMET module “Snowpack and Its Assessment.”
• Every forecast situation is different. In some cases, you’ll have abundant weather and snowpack observations. In other cases, local weather and snowpack data will be sparse to non-existent and you’ll have to rely solely on the forecasted weather conditions to assess avalanche potential. While this is challenging, it’s not impossible. Knowing what weather criteria are conducive to avalanche production is key to estimating avalanche potential.