Avalanche Bulletin Sunday, 20.04.2014, at 07:30
Fresh snowdrift is prone to triggering!
Avalanche danger in Tirol’s backcountry touring regions is predominantly at level moderate. Along the Main Alpine Ridge the peril above 2200 m can be considerable from place to place. The major hazards stem from older and fresh snowdrift accumulations which are inadequately bonded with the old snowpack and can be triggered as avalanches even by minimum additional loading in some places. Avalanche prone locations are found on wind loaded slopes and in areas adjacent to ridgelines in all aspects, primarily above approximately 2200 m. In steep starting zones, in addition, naturally triggered superficial loose avalanches are possible which can subsequently release instable snowdrift accumulations.
Over the last 24 hours along the Main Alpine Ridge and in East Tirol there was an additional 10 cm of snowfall. High altitude southeasterly winds were above transport velocity at high and high-alpine altitudes, thus giving rise to new snowdrift accumulations. These drifts are inadequately bonded to the snow base beneath them. Due to persistently low, wintery temperatures, the snowdrift masses tend to be brittle and thus, trigger-sensitive.
Alpine Weather Forecast (ZAMG-Weather Service Innsbruck)
Weather in general: Tirol is still wedged between two small low pressure zones, caught in moist, instable air masses. One of these lows will swell up over the next few days, the air will remain prone to showers. Mountain weather today: high fogbanks will disperse, bringing ample sunshine except in the Kaiser range, Tauern and East Tirol’s mountains. Convective cloud build-up during the course of the day, increasing likelihood of showers (snowfall level at 2200 m). Temperature at 2000 m, +3 degrees; at 3000 m, -4 degrees.
Short Term Development
Moderate avalanche danger widespread. Beware fresh snowdrift.
[Author: Rudi Mair]
[Translated by Jeffrey McCabe]
Current danger pattern(s)
Experience has shown that even over the course of highly varied winters, nearly identical potential-avalanche scenarios repeatedly arise as recurring danger patterns and are responsible for the greater part of avalanche accidents. An analysis of these patterns was published in the practical handbook "Avalanche - Recognizing the 10 Decisive Danger Patterns" by Rudi Mair and Patrick Nairz in November 2010.
Danger pattern (dp) 6 - cold, loose, new fallen snow and wind
"Wind is the architect of avalanches" this classic adage of Wilhelm Paulcke from the 1930s still has unaltered validity today. Wind influences both falling snow and already deposited snow, it is one of the major formative factors in potential avalanches. If the snow is loosely packed and dry, wind always leads to its transport, thus increasing the danger of avalanches. The colder the transported snow is, the more sensitively it reacts to additional loading, since it becomes even more brittle. This danger pattern is distinct from GM.5 in that the cold, loosely packed snow has not formed over a prolonged cold period, but in a very short time. That means, it either snowed just previous, in low temperatures without wind, and subsequently the wind begins to blow; or it begins to snow without wind, and the wind increases in velocity during the snowfall. This pattern is easy to recognize as a rule.