
Spring is the time of strong sun and melting snow. The greatest influences on the behaviour of the snow pack at this time are solar radiation, air temperature, wind,cloud cover and water. The whole snow-pack slowly becomes isotherm, (the same temperature from bottom to top) and goes through many melt freeze cycles until the snow disappears either in the form of running water, or water vapour, in a process called sublimation. This refers to water molecules passing from ice to water vapour without undergoing the melting process. Sublimation is an important process in the total energy balance of the snowpack, and plays a defining roll throughout the winter on the ever-changing snowpack stability.
In Spring small snowfalls and storm cycles are followed by periods of fine and warmer weather. The snowpack is undergoing strong overall changes from layers that contain various individual types of snow crystals, bonding into a single homogeneous layer. The avalanche hazard varies daily, generally in 24 hour cycles, between night and day/ colder and warmer.
Wet snow avalanchesWet slides occur when warm temperatures melt the surface snow layers and begin to saturate them with water. The water weakens the bonds between layers and avalanches often occur. Wet avalanches move more slowly than dry avalanches but they can still be dangerous:
• If temperatures have been above freezing for extended periods then wet avalanches will most likely occur
• If you are sinking into wet snow up to your ankles or deeper , the snow is wet and prone to avalanche
• If you squeeze a hand full of snow and it makes your glove wet or if water literally drips out of the snow, the snow may be prone to avalanche

The photo above shows typical spring conditions after a light snowfall. The first fine day brings strong warming of the new snow on sunny slopes. The new snow although not deep around the tops has started with a point form slide out of the rocky areas, widening as it rolls down over the open slopes and finally being channelled into a gully near the bottom. Although it started out only a few centimetres deep, this spring slide has amassed a depth of several meters in depth at the bottom. These kinds of slides are typically slow moving compared to dry slab avalanches /powder avalanche.
Below a close up of point formed damp/wet snow avalanche starting under a bluff. This is typical. Often started by a single stone falling from the cliff as the day and snow warms, or a single grain of snow which has “rolled” and started a chain effect.

Other wet snow avalanches fail on a plane or layer and have a slab shape appearance at the top,


Typical wet snow av. debris.
Rainfall itself into spring snow is the super lub and will bring down everything that is ready to move and plenty that is not. It combines all the elements to produce wet snow avalanches. Water, added warmth, weight.
Spring time also brings good walking conditions if the surface is hard, and generally safe conditions to travel as far as avalanche hazard is concerned. That is until the snow surface has softened to the point where
one is starting to fall through it. At this time of day, it’s easier and safer to seek routes that take one onto open and snow free ridges. Don’t forget that not only do you have to be able to climb safely, but one must also be able to find the way home safely, so pick you routes that offer you a safe homeward journey in the evening. Late afternoons and evenings are the time in the spring when wet snow avalanches and glide cracks opening further and totally failing, are most common.

Walking over a lightly softened spring crust.
Glide cracks.It’s common in spring to see wide cracks opening up in the snowpack on steep slopes or slopes that are convex near the top. The spring snow has a lot of water in it and the whole depth of snow may slowly start to slide, especially over grassy areas or surfaces such as smooth rock. These ground cacks open slowly over a period of days or even weeks, during spring melt/freeze cycles, which are normally night and day cycles.
The pic below illustrates well how a crack can be quite safe to move around during the morning or anytime the surface is still solid enough to carry your weight without sinking through for more than a few centimetres. This crack may have been open for several days of longer.

On a previous day someone has walked over it leaving footprints, and at some point there has been some wind which has blown a small amount of new or wind scoured snow into the crack. Over a period of weeks the cracks can open up to several meters or tens of meters width, and still be perfectly safe to move around, as long as the surface is hard as you approach them. These Chamois certainly have no worries about the snowpack and are enjoying some of the spring growth behind the crack which the strong spring sun will be encouraging.

Occasionally the snow at base of the slope on which the crack is opening up, will fail, and the whole slope will come down. This only occurs if there is a huge amount of free water in the snow, usually running and lubricating the surface below the snowpack. If you can’t easily walk on the snow surface and it’s rotten to the point where you sink though to below your ankles, in extreme cases thighs, then it’s time to pick a safer route.

Above a failed Glide Crack, the thin layer of dirty white snow over grass or rock indicates that the snow has only recently failed. The strong solar radiation onto the grassy area would have otherwise melted the thin layer of remaining snow. The long shadows on the snow cast by the trees indicate the photo was made early morning or toward evening.
Other Hazards.Frozen surface layers. The hard surface layer encountered mornings or during colder periods in spring brings other hazards. Steep slopes can only be negotiated with a degree of safety on skis,
if you are an experienced skier, but preferably with crampons and ice axe. In even more extreme weather cycles the surface can become as slick as a mirror, as pictured below. Rainfall or miniscule water particles blown onto the surface at around freezing point have produced a hard polished surface and under these conditions anyone venturing onto any slope without appropriate gear is risking life and limb. Often the slope may appear innocuous because it has a good run out at the bottom, but any rocks pocking out through the surface will become deadly as one slides over them at high speed. The speeds attained during an uncontrollable slide are frightening and more than often fatal.

If you are a hunter come across something like the above,and wish to negotiate it safely, the only way is to seek another gentle(very) route around the hazard to a lower level where surface contitions may be different.
White outNot confined to the spring, white out is a hazard that can be encountered anytime anywhere, but is particularly disorientating in a contrast free snowscape. Don’t climb into a white out if you are not very very familiar with the area. Even then, one can become quickly disorientated. Staying below thick cloud, mist and fog in a contrast rich environment is recommended. In the pic below there are actually five persons standing only about 20 m from the camera.


A contrast rich environment offers some visibility and waypoints to follow a route. However small scale hazards such as sharp changes in the terrain or small creeks may remain totally invisible even at very close range. General direction can only be guessed at over longer distances and a slow change of bearing is inevitable unless one has an intimate knowledge of the way points.

Disorientation sets in rapidly if there is no horizon and no points of reference, such as trees, rock faces, streams etc. The risk of wandering into dangerous terrain is very high, and often deadly. Even a small fall into a creek bed can have serious consequences.
Below the snowline the visibility is better, but large scale disorientation is likely unless you are familiar and at home in the terrain.

Whiteouts due to snowfall will also make assessment of the avalanche risk more difficult in that one cannot see what is above and may in fact hide visable sign of strong winds and snow transport along the tops.. Some valleys are in in total wind-shade and all appears calm. Often the only indication of snow transport above you is the sounds of the storm roaring through the cliffs and bluff systems above.
A bracing experience.

Happy hunting.