Snowpack Observation

By 28. November 2020SLABS_en

I nformation on the structure and stability of the snowpack within an area is essential to assessing current and future avalanche conditions. In certain applications, starting zones may be inaccessible and snowpack properties can be estimated with careful analysis of past and present weather and avalanche events. Snowpack parameters vary in time and space, and observation schemes should address these variations. Snowpack information is generally observed and recorded separately from the snow and weather observations. However, some basic weather observations are typically made in conjunction with snowpack observations.

Objectives

The primary objective of any observer working in avalanche terrain is safety. Secondary objectives may include observing and recording the current structure and stability of the snowpack. Other objectives will depend on the type of operation.

Standard snowpack observations

The snowpack parameters observed and the detail of those observations will depend on the particular forecasting problem. This post presents an outline for daily snowpack observations. Parameters one through five and parameter seven will be useful for most avalanche forecasting programs. Individual programs and field workers should select snowpack properties (parameter six) from those listed in this post to supply the information needed for their specific application.

1. Date

Record the date on which the observation was made (DD.MM.YYYY).

2. Time

Record the local time at which the observation was begun (24-hour clock).

3. Observer

Record the name or names of the personnel that made the observation.

4. Site Characteristics

  • Observation Location – Record the nearest prominent topographic landmark (mountain, pass, drainage, avalanche path, etc.), political landmark (town, road mile, etc.), or geographic coordinates (latitude/longitude or UTM). If observing a fracture line profile, note the location within the avalanche path.
  • Aspect – Record the direction that the slope faces where the observation was made (i.e. N, NE, E, SE, S, SW, W, NW, flat; or degrees azimuth).
  • Elevation – Record the elevation of the observation site above sea level (meters).
  • Slope Angle – Record the incline of the slope where the observation was made (degrees).

5. Current Weather

  • Sky Conditions – Record the sky conditions as Clear, Few, Scattered, Broken, Overcast, or Obscured (or scale in oktas).
  • Air temperature – Record the current air temperature in degrees Celsius to the nearest 0.5 °C.
  • Precipitation Type and Rate – Record the precipitation type (snow, graupel, rain, hail) and rate
  • Wind – Record the measured or estimated wind speed and direction.
  • Surface Penetration – Record the surface penetration of boot or skis in cm.

6. Snowpack Properties

Observe and record the necessary snowpack properties as described in post.

7. Avalanche Potential

Information about the prevailing avalanche conditions is provided by: fresh avalanche deposits, danger signs (e.g. whumpfing, crack formation, glide cracks), wind signs, amount of new snow, blasting results of artificial releases.

Avalanche conditions can be grouped by region, aspect, slope angle, elevation, terrain types (e.g. in proximity to ridges) or snow properties (areas with less snow).

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