Weather

Mountain Weather Forecasting

The Snowpack, Avalanches, and Weather
The snowpack is created by weather and evolves over time under the influence of weather. Extrapolating from current snowpack conditions and stability into the future (that is, producing an Avalanche Forecast) requires looking at and understanding weather forecasts. It’s important to understand that the accuracy of avalanche forecasts are largely related to the weather forecast. If the weather forecast is off, the avalanche forecast for that period likley be off as well. Given how large our avalanche forecast regions are, there's almost always variability (sometimes a lot of variability) in the local forecasts for specific places within the region. So even when the weather forecast is accurate in general, there's almost certainly going to be some places where it's less accurate and that in turn may be reflected by local variability in the accuracy of avalanche forecasts. 

At the CAC’s Public Avalanche Warning Service, we do our best to get the weather as right as we can—not an easy task given the complexity of weather and the difficulty of predicting it in mountainous terrain. Even professional meteorologists are often wrong when forecasting mountain weather, more so the farther out in time the forecast goes. We then do our best to provide you with a variety of weather forecast information. This includes regional weather forecast overviews as well as links to various products and services that can help you generate your own local mountain weather forecast.

Regional Weather Forecast Overview
For most users, generating their own mountain weather forecast is too time-consuming and technical a process and the best place to get a weather forecast is from the Public Avalanche Forecasts where, every day a weather forecast overview is provided for each forecast region. This overview is found by clicking on the Forecast Details tab above the Public Avalanche Forecast for the region you are interested in then looking for the Weather Forecast section. Here, the avalanche forecaster summarizes model output, technical weather synopses, and daily consultation with a professional meterologist.

Mountain Weather Forecasting 101
The overview is, of course, an average, big-picture look at large regions and many users want more detailed information. Many of the weather forecasting resources CAC forecasters use to produce their daily regional overview are found in the Weather Images link on the side panel to the left. For high end, professional level users, here’s a link from to the CAA's professional weather links. These two sets of links provide more or less all the raw data the CAC forecasters and industry professionals use to analyze and forecast avalanche hazard and prepare risk management plans.

There are many other online resources available. Check Environment Canada's website and look in the Radar and Satellite, Aviation Weather, and Analyses and Modelling tabs. There are numerous products applicable to western Canada and especially BC in the University of Washington's Department of Atmospheric Services website, particularly in the Weather Loops section but also many of the other sections.

It’s best to start simple. Try this for a introductory level daily routine:

  1. Look at the big picture for the last 12 hours to get an idea of the general pattern.
  2. Check the current upper level analysis to see what’s happening now.
  3. Review the jet stream forecast to get a big-picture idea of what’s likely to happen next.
  4. Look at a large scale model to get an idea of how the major incoming weather systems are shaping up.
  5. Check medium scale models to zoom in on precipitation and winds/temperatures.
  6. Compare all this with your local public weather forecasts and the overview in the CAC’s daily avalanche forecasts to develop your own picture of what the weather will do in your area.
  7. Eventually, you’ll want to compare a couple of different models in steps 3, 4, and 5 to see if there is agreement or not. If yes, confidence in the forecast may be higher; if no then there’s more uncertainty about what is likely to happen next.

Please note this is a highly simplified overview of a full weather forecasting process that you need to follow on a regular basis. Starting the process of making your own mountain weather forecasts on Friday night to figure out what to do for the weekend is not a great way to begin your planning process. Just like keeping tabs on avalanche conditions by reading the avalanche forecasts regularly, developing a daily weather forecasting routine and following it religiously is required to get a handle on the weather and stay current. There are many more resources available than noted in these steps and everyone will eventually develop their own favourites. The description above is not intended to be definitive or comprehensive; rather it shows the basic steps involved and presents examples of some products often used in these steps.

Learning More
If this is all bafflegab to you, you can simply rely on the daily weather forecast overview provided in the  Avalanche Forecasts as noted above. If you want to get some training, take a look at the Canadian Avalanche Association’s Mountain Weather Courses. To learn more about the technical aspects of weather and weather forecasting terminology, check Haby’s Weather Forecasting Hints. Environment Canada has an Educational Resource section on their website that includes a Weather and Meteorology tutorial. And the MetEd website has a section that provides online Avalanche and Weather training.