How we produce Avalanche Reports
Avalanche Forecast Areas
When producing daily avalanche forecasts for a region, the whole landscape and summits as indicated on the home page map (see fig 1) are considered by SAIS forecasters.
The “core” forecast area is within this region and is the area most visited by the SAIS forecaster. This is the area that is recognised as the most popular location for those engaging in winter activities. Knowledge from this “core” area is applied to the more outlying mountains in the forecast region where field observations are carried out in turn as the winter progresses, or specific snowpack assessments are required.
Fig 1 – SAIS Forecast Regions
How we use the Met Office weather forecast
Avalanche forecasts are produced using detailed bespoke weather forecasts provided to the SAIS by the Met Office.
The “mountain weather forecast team” based in Aberdeen (see fig 2) compile the weather forecasts using information from the met office supercomputer based in Exeter and their specialist knowledge. The weather forecasts we receive on a daily basis are quite specific to each area and are provided for our “core” area.
The duty avalanche forecaster uses their area knowledge of topography to determine the weather forecasts range of impact on the snowpack throughout the region and their level confidence in its application. Typically, SAIS forecasters consider that beyond the “core” area, their confidence in the weather’s impact on the snowpack can be reduced, this however depends on the weather type and airmass direction. ( eg arctic, maritime, continental etc).
Although SAIS avalanche forecast areas may not be too far apart, weather variation and snowpack type can differ significantly. Air mass types such as maritime or continental in conjunction with topography variation present great variation from area to area. Therefore the snowpack and avalanche forecast for each area will be different, often, even in adjacent areas.
Fig 2 – Met Office data for Torridon area – centred on Liathach – Data from Met Office supercomputer
How we produce Avalanche Reports
For the avalanche reports, weather information is used in conjunction with snowpack information such as; snow depth, snowpack sensitivity, likelihood of avalanche release and hazard distribution.
This is gathered by the SAIS avalanche forecasters on their daily travels, on ski or on foot, using visual and practical observations at all available altitudes and, on many slope aspects.
The avalanche forecasters knowledge of an SAIS forecast regions snowpack stability, rapidly evolves from the start of the winter as data gathering progresses. With this knowledge, the impact of weather conditions on the snowpack can be foreseen and the avalanche hazard distribution for the whole forecast region can be considered more effectively.
Field observations in the N Cairngorms
