Avalanches in the Tatras are a phenomenon that poses a serious threat to tourists. Powerful masses of snow, moving at high speed, are extremely dangerous. No wonder - snow rushing down the mountain can move at speeds of up to 250 km/h. One cubic metre of powder snow weighs up to 200 kg, wet snow 700 to 800 kg, and ice up to around 900 kg. An avalanche can also carry stones, boulders or trees with it.
The causes of avalanches are complex and can include weather conditions such as heavy snowfall, strong winds and temperature changes. In addition, the instability of snow layers can be caused by external factors such as snow loads from people or animals.
There are 5 degrees of avalanche danger. TOPR describes them on its website as follows:
1. LOW - The snowpack is generally well bonded and stable. Triggering is generally only possible from high additional loads (e.g. single hiker, two or more skiers or snowboarders moving without the correct spacing, snow groomer, explosives) in a few places on very steep or extreme slopes (terrain particularly unfavourable due to slope gradient of more than approximately 40° or particularly unfavourable due to terrain, proximity to ridge or properties of the ground, e.g. reduced grip). The possibility of spontaneous descent of small (the moving snow usually stops before the end of the slope, causes minimal danger of burial of a person, the danger of a fall is greater) and medium avalanches (the avalanche usually stops at the end of the slope, may burrow, injure or kill a person).
2. moderate - the snowpack is generally well bonded, but on some steep slopes (terrain with gradient higher than approx. 30°) it is moderately bonded. Triggering is possible mostly from high additional loads (single hiker, two or more skiers or snowboarders moving without maintaining correct spacing, snow groomer, explosives), especially on steep slopes (terrain steeper than approximately 30°) indicated in the avalanche communication. The spontaneous descent of very large avalanches (an avalanche usually reaches flat terrain, with gradients of much less than 30°, over distances greater than 50 m, may reach the valley floor) is unlikely. Partially unfavourable conditions for mountain tourism. Hiking requires the ability to assess local avalanche danger, to choose the right route and to take elementary safety precautions on all steep slopes (above 30°) and especially on those indicated in the avalanche communication as unfavourable in terms of exposure or altitude.
3. HIGH - The snowpack on many steep slopes (above 30°) is moderately to poorly bonded. Triggering is possible even from low additional loads (a lone skier or snowboarder riding smoothly, without falling, a hiker wearing snowshoes, a group maintaining correct gaps between participants, i.e. at least 10 m), especially on steep slopes (above 30°) indicated in the avalanche communication. In some situations large (an avalanche usually reaches flat terrain, with gradients of much less than 30°, over distances of less than 50 m, it can burrow and destroy a car, damage a truck, destroy a small building, break single trees), and in a few cases also very large avalanches (an avalanche usually reaches flat terrain, with a gradient of significantly less than 30°, over distances greater than 50 m, may reach the valley floor, may bury and destroy a railway car, a large truck, several buildings or a section of forest) may descend spontaneously. Conditions for hiking largely unfavourable. Navigating in such conditionsh requires a great deal of experience and skill and having a very high ability to assess the local avalanche danger. Steep slopes (above 30°), especially those indicated in the avalanche communication as unfavourable in terms of aspect or altitude, should be avoided. Elementary safety precautions must be taken.
4. HIGH - The snowpack on most steep slopes (above 30°) is poorly bonded. Triggering of an avalanche is likely even from low additional loads (lone skier or snowboarder going smoothly, no falls, hiker moving in snowshoes, group maintaining correct spacing between participants, at least 10 m) on many steep slopes (above 30°). In some cases numerous large (an avalanche usually reaches a flat terrain, with a slope of much less than 30°, over distances of less than 50 m, may bury and destroy a passenger car, damage a truck, destroy a small building, break single trees) and often very large (an avalanche usually reaches a flat terrain, with a slope of much less than 30°, over distances of more than 50 m, may reach the valley floor, may bury and destroy a railway car, a large truck, several buildings or a section of forest) are to be expected. Conditions for hiking definitely unfavourable. It is advisable to abandon all outings into high mountain terrain. Stay within the limits of moderately steep slopes (terrain with a slope of less than about 30°) and take into account the extent of avalanches from higher slopes.
Grade 5 VERY HIGH - The snowpack is poorly bonded and far from unstable. Numerous spontaneous very large (avalanche usually reaches the flat terrain, with gradient significantly less than 30°, over distances greater than 50 m, may reach the bottom of the valley, may bury and destroy a railway car, a large truck, several buildings or a piece of forest) and often extremely large avalanches (avalanche reaches the bottom of the valley and may cause significant changes in the landscape, possible catastrophic damage) are to be expected, even on moderately steep slopes (with gradient less than about 30°). Conditions for tourism extremely unfavourable (catastrophic situation). It is advised to refrain from any mountaineering activities and to stay in areas not at avalanche risk.
You can check the current avalanche danger level on the TOPR website.
In February 2023, due to avalanche grade 4, after very heavy snowfall, the Tatra National Park closed all trails in the Tatra Mountains to tourists. Level 5 was announced in January 2002. At that time also all trails were closed. Sixty to eighty centimetres of fresh snow fell within a day, and a massive snow avalanche came down the Żandarmerie Cave. Fortunately, the road to Morskie Oko was already closed by then. Previously, the 'avalanche five' had been announced only a few times. After that date, the avalanche danger in the Tatras was never again so high.
If you want to think about going to the high mountains in winter, you need to complete an avalanche course for your own safety. It is through this course that you will gain knowledge and practical skills. For example, practical use of the avalanche ABC, i.e. detector, probe and spatula. You can also recognise the terrain and analyse the current weather and avalanche conditions.