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.
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.
Specific measurements and observations will be dependent on the type of operation, but in general the objective is to observe and record the current structure and stability of the snowpack.
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.
Record the date on which the observation was made (YYYYMMDD).
Record the local time at which the observation was begun (24-hour clock).
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, or degrees azimuth).
- Elevation – Record the elevation of the observation site (feet or 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.
- Air temperature – Record the current air temperature to the nearest 0.5 °C (or whole °F).
- Precipitation Type and Rate – Record the precipitation type and rate
- Wind – Record the wind speed and direction.
- Surface Penetration – Record the surface penetration (Section 1.18).
6. Snowpack Properties
Observe and record the necessary snowpack properties as described in post (TAG).
7. Avalanche Potential
Record one or more of the parameters as applicable to the operation. Avalanche conditions can be grouped by region, aspect, slope angle range (i.e. 35°-40°), or obvious snow properties (such as recently wind loaded or amount of new snow). In this case a separate stability, danger, or hazard rating should be given for each group.
- A) Snow Stability
Forecast – record the snow stability stated in the morning meeting or current forecast.
Observed – record the snow stability observed at this location.
- B) Avalanche Danger
Forecast – record the avalanche danger stated in the current avalanche advisory.
Observed – record the avalanche danger assessed at this location.
- C) Avalanche Hazard
Forecast – record the avalanche hazard currently stated by the program
Observed – record the avalanche hazard assessed at this location.