avalanche hazard level 1 (continuous snow - cover, few snow on the ground, depth hoar layers)...
TRANSCRIPT
Avalanche hazard level 1
(Continuous snow - cover, few snow on the ground, depth hoar layers)
Dolomites - January 2006 the 16th
ARPAV – Centro Valanghe Arabba
Condition for the avalanche hazard level: 1 - low
Degree of Degree of dangerdanger SnowpackSnowpack Avalanche probability Avalanche probability
lowlow
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.
Study Area (1800 km2)
Avalanche bulletin
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.
Snow data
Typical snow profile of on January 2006 the 16th
A lot of layer of:Faceted crystalDepth Hoar
Snowpack microstructure: grain type
Typical Rutschblock R=716.01.2006
Altitude: 2100 m a.sl.Exp.: Est
Snowpack:natural stability index Sn 38
• Natural stability index =2,1 – 2,3
• Skier stability index =1,4 – 1,7
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
BC
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
EF
Avalanche activity
SluffSluffLength < 50 m
Volume < 100 m3
Small avalancheSmall avalancheLength <100 m
Volume < 1.000 m3
Medium avalancheMedium avalanche
Length <1.000 m
Volume < 10.000 m3
Large avalancheLarge avalanche Length <1.000 m
Volume < 10.000 m3
natural No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
low additional load
No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
large additional load
No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
No avalanche (few some many numerous)
zone of the avalanches observation
Meteorological data
Wind speed and direction
Air Temperature
Average (1984-2005)
New Snow
New Snow New Snow
24 h (HN)24 h (HN)
HW HW
24 h24 h3 days new 3 days new Snow sumSnow 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
Summary of the informations and of the data and their importance
for the avalanche forecast for the day January the 16th
Avalanche forecast: Anselmo Cagnati, Mauro Valt and Renato Zasso
Analysis checklistAnalysis checklist
Factor Data Stability?
Y/N/?
Importance
I. Avalanche Activity and Stability TestsI. Avalanche Activity and Stability Tests
Avalanche Activity None in last 2 days YY Medium
Stability Test R7 YY High
II. Snowpack ObservationsII. Snowpack Observations
Profile Weak resistance ( little thickness) Y?Y? High/Low
Settlement Few NN Low
Temperature Long period of low temperatures N - YN - Y Low
Temperature Gradient High 33 °C/m N - YN - Y Low
Snowpack Height 50 – 90 cm YY High
III. Meteorological ObservationsIII. Meteorological Observations
Precipitation None in last 3 days YY Low
Wind Speed Weaks NN High
Wind Direction NW NN Low
Air Temperature Low Air Temperature –12/ -17°C NN Low
Weather forecast Weaks wind in the 24 h, strengthening in the next 72 h YY High
Auxiliary matrix for the avalanche report
Photographic documentation
None sluff or small avalanche on the S-W slopes (Tre Cime di Lavaredo)
None sluff or small avalanche on the S slopes (Sappada)
None sluff or small avalanche on the S-E slopes (M.te Piz Boè, Campolongo)
None avalanche in skiing out of the bound (N-E slopes) (M.te Civetta)
None avalanche in skiing out of the bound (S-E slopes) (M.te Civetta, Falcade)
Backcountry ski on extremely steep slope (Monte Pelmo)
Thanks