1. Avalanche hazard level 1 (Continuous snow coverage, few snow to the ground, depth hoar layers) Dolomites - January 2006 the 16 th ARPAV – Centro Valanghe Arabba

2. Condition for the avalanche hazard level: low Degree of danger Snowpack Avalanche probability low The snowpack is generally well bonded and stable or to weak cohesion and without tensions. Triggering is generally possible only with high additional loads [2] and few very steep extreme slopes. Only a few small natural avalanches (sluffs) possible. Indications for excursionists mountain, climber, backcountry skiers and ski out of the bound Indications for roads, ski area and countries Generally favourable conditions. Any indication.

3. Study Area (1800 km 2 )

4. Snow data

5. Typical snow profile of on January 2006 the 16 th A lot of layer of: Faceted crystal Depth Hoar

6. Snowpack microstructure: grain type

7. Typical Rutschblock R=7 16.01.2006 Altitude: 2100 m a.sl. Exp.: Est

8. Snowpack Natural stability index Sn 38 Natural stability index =2,1 – 2,3 Skier stability index =1,4 – 1,7

9. Snow cover distribution 16.01.2006 A Snow depth: –1500 m (a.s.l): 20 – 60 cm –2000 m (a.s.l.): 50 – 90 cm B Snow distributions: –On the southern slopes the snow cover is discontinuous to 1700 m –On the slopes in shadow the snow is present at low altitude. C Snow surface: –The superficial layer of the snow cover presents weak cohesion at every altitudes and in all the exposures with some wind crusts. A B C

10. Avalanche activity D Natural avalanches –Any observed avalanche. E Skiers avalanche –Any observed avalanche (Ski out of bound even on extreme steep slopes) F Wind activity: –Weak wind activity (all exposures) D E F

11. Avalanche activity Sluff Length < 50 m Volume < 100 m 3 Small avalanche Length <100 m Volume < 1.000 m 3 Medium avalanche Length <1.000 m Volume < 10.000 m 3 Large avalanche Large avalanche Length <1.000 m Volume < 10.000 m 3 natural No avalanche (  few  some  many  numerous) low additional load No avalanche (  few  some  many  numerous) large additional load No avalanche (  few  some  many  numerous) zone of the avalanches observation

12. Meteorological data

13. Wind speed and direction

14. Air Temperature Average (1984-2005)

15. New Snow 24 h (HN) 24 h (HN)HW 24 h 3 days new Snow sum Manual weather stations Belluno, 290 m 0 cm===0 cm Falcade, 1200 m 0 cm===0 cm Cortina,1200 m 0 cm===0 cm Arabba, 1600 m 0 cm===0 cm Automatic weather stations C.Pradazzo,2200 m 0 cm===0 cm M.A.Ornella, 2200 m 0 cm===0 cm

16. Summary of the informations and of the data and their importance for the avalanche forecast for the day January the 16 th Avalanche forecast: Anselmo Cagnati, Mauro Valt and Renato Zasso

17. Analysis checklist FactorData Stability? Y/N/? Importance I. Avalanche Activity and Stability Tests Avalanche ActivityNone in last 2 daysY Medium Stability TestR7Y High II. Snowpack Observations ProfileWeak resistance ( little thickness)Y? High/Low SettlementFewN Low TemperatureLong period of low temperatures N - Y Low Temperature GradientHigh 33 °C/m N - Y Low Snowpack Height50 – 90 cmY High III. Meteorological Observations PrecipitationNone in last 3 daysY Low Wind SpeedWeaksN High Wind DirectionNWN Low Air TemperatureLow Air Temperature –12/ -17°CN Low Weather forecastWeaks wind in the 24 h, strengthening in the next 72 hY High

18. Auxiliary matrix for the avalanche report

19. Avalanche bulletin

20. Situations: Avalanche hazard: low (level 1) Since the beginning of the last week the weather kept on being good with mainly clear sky ad very good visibility. Since yesterday temperatures felt down especially aloft and the thermal inversion has almost disappeared. Winds were generally light, also if local strengthening were registered only on the most high altitude on the Dolomites. With low temperatures, snow had a significant cooling at every altitude with consequent increasing of kinetic growth crystals and surface hoar which in some cases is well grown. Only on the extreme steep slopes exposed to S and W the surface layer presents local sun-refrozen crusts which are however not very much strengthening. The avalanche danger is generally low and eventual artificial releases, generally only with large additional load, are possible only on isolated extremely steep slopes characterized by snow drift deposits. Since the central hours of the day, with the sun, on the grassy steep slopes or at the base of the rocks single little natural avalanches of moist snow might occur. Wind slab on faceted crystals, soft snow or crusts. Extremely steep slopes.

21. Photographic documentation

22. None sluff or small avalanche on the S-W slopes (Tre Cime di Lavaredo)

23. None sluff or small avalanche on the S slopes (Sappada)

24. None sluff or small avalanche on the S-E slopes (M.te Piz Boè, Campolongo)

25. None avalanche in skiing out of the bound (N-E slopes) (M.te Civetta)

26. None avalanche in skiing out of the bound (S-E slopes) (M.te Civetta, Falcade)

27. Backcountry ski on extremely steep slope (Monte Pelmo)

28. Thanks