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SIERRA NEVADA AVALANCHE INFORMATION SERVICE (SNAIS)
As an aid to climbers, mountaineers, ski tourers and walkers for this winter season, we are aiming to produce an Avalanche Information System based on the highly successful Scottish service that has been in use for many years. As we are in the hills most days during the winter and are consistently in a position to evaluate the danger, this safety information will be made available to all interested parties through a BLOG called....
sierrasnow.info
. This new service will start operation in mid-December each year and will be updated as and when conditions materially change. We welcome any comments or remarks about the conditions.

Degree of hazard

Snowpack stability

Avalanche probability

For traffic & residential areas

For off-piste & back-country activities

1(low)

 The snowpack is generally well bonded and stable. Triggering is possible only with high additional loads2 on a few very steep extreme slopes4. Only a few small natural6 avalanches (sluffs) possible. No hazard from avalanches. Virtually no restrictions on off-piste & back-country skiing & travel.

2

(moderate)

 The snowpack is moderately well bonded on some1 steep3 slopes, otherwise generally well bonded. Triggering is possible with high additional loads2, particularly on the steep3 slopes indicated in the bulletin. Large natural6 avalanches not likely. Virtually no hazard from natural avalanches. Generally favourable conditions. Routes should still be selected with care, especially on steep3 slopes of the aspect5 and altitude indicated.

3

(considerable)

 The snowpack is moderately to weakly bonded on many1 steep3 slopes. Triggering is possible, sometimes even with low additional loads2. The bulletin may indicate many slopes which are particularly affected. In certain conditions, medium and occasionally large sized natural6 avalanches may occur. Traffic and individual buildings in hazardous areas are at risk in certain cases. Precautions should be taken in these areas. Off-piste and back-country skiing and travel should only be carried out by experienced persons able to evaluate avalanche hazard. Steep3 slopes of the aspect5 and altitude indicated should be avoided.

4

(high)

 The snowpack is weakly bonded in most1 places. Triggering is probable even with low additional loads2 on many steep3 slopes. In some conditions, frequent medium or large sized natural6 avalanches are likely. Avalanches may be of large magnitude. In hazardous areas, closure of road and other transport is recommended in some circumstances. Off-piste and back-country skiing and travel should be restricted to low-angled slopes; areas at the bottom of slopes may also be hazardous.

5

(very high)

 The snowpack is generally weakly bonded and largely unstable. Numerous large natural6 avalanches are likely, even on moderately steep terrain. Extensive safety measures (closures and evacuation) are necessary. No off-piste or back country skiing or travel should be undertaken.

Notes

1 Generally described in more detail in the avalanche bulletin (e.g.altitude, slope aspect, type of terrain, etc.).
2 Additional load: high - e.g. group of skiers, pistemachine, avalanche blasting.low - e.g. skier, walker.
3 Steep slopes: slopes with an incline of more than30 degrees.
4 Steep extreme slopes: those which are particularlyunfavourable in terms of the incline, terrain profile, proximity to ridge,smoothness of underlying ground surface.
5 Aspect: compass bearing directly down the slope.
6 Natural: Without human assistance.

 

   

 

 

 

 

 

 
Born on: 10/07/2002