Avalanche Assessment Data Sheet

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Assessment Date & Time: 18/08/2018 1234hrs
Observer Name/s: GK + GK
Assessment Location: Upper Otira Valley - TL Flank (E1479217 N5248586)   Altitude (m): 1540m
Slope Angle (xº) & Aspect (1-360º Mag.): 37º, 270º

Current Weather Conditions: Clear and fine
Air Temperature (ºC): 7.1ºC
Wind Direction / Strength (1-360º Mag. / Kmph): 0º @ 0km/h
Hygrometer RH (%): 32% Stable
Uncorrected Barometer (mb): 924mb Falling

Previous Activity: Wet snow avalanches to Class 3-4. Storm-slab release at 1800m on East aspect, crown=1m, width=150m.
Current Activity: Face deload sluffs Class 1 - 2 on northern aspects starting at 1800-1900m. Considerable radiation snowballing.

Snow Crystal Descriptor Codes

New snow Partly decomposed snow Small rounds Faceted grains Rounding facets Melt freeze crust Graupel Ice layer Needles
Columns Plates Melt freeze/wet Clustered grains Polycrystals Slush Rounded grains Depth hoar Surface hoar

Hardness Descriptor Codes (Hand Test)

Very soft - Fist Soft - Four fingers Medium hard - One finger Very hard - Pencil Hard - Knife Ice - Impenetrable

Snow Structure Data

Surface10cm 20cm30cm40cm 50cm60cm70cm 80cm90cm100cm110cm120cm130cm
0.3ºC -0.3ºC 0.0ºC 0.3ºC 0.3ºC 0.2ºC 0.2ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.0ºC
140cm150cm 160cm170cm180cm 190cm200cm210cm 220cm230cm240cm250cm260cm270cm
0.0ºC 0.1ºC 0.1ºC 0.1ºC 0.0ºC                  
Layer Thickness
(Hand Test)
Size (mm)
1 12 S 0.2 A,B Good 280 34mm Dry snow - rounded
2 1.0
MH 0.3-0.4 C OK CT0 300 3mm Rain crust
3 7.0
MH 0.3 C OK CT0 460 32mm  
4 6.0
MH 0.2 C OK 460 28mm  
5 2.0
MH 0.3 C Poor 420 8mm Melt/freeze crust
6 4.0
S 0.8-1.0 G OK 400 16mm  
7 3.0
S 1.0 C Poor 480 14mm  
8 15.0
VS 1.2 C Good CT0 360 54mm  
9 39.0
S 1.0 C OK CT4 500 195mm Free water present, poor sintered bonds
10 19.0
MH 0.8 C OK CT3 528 100mm Free water present
11 17.0
MH 1.0 C OK CT1 480 82mm Free water present
12 17.0
S 0.8 C Good 540 92mm Impermeable layer
13 38.0
MH 1.5-2.0 L Poor 480 182mm Free water present, wet snow - sugary, 120cm to rock
Pack Statistics
Snowpack Depth: 300.0cm
Snowpack Weight: Indeterminate!

Pack Analysis :
Isothermic snowpack containing two crusts and a deep impermeable layer. A considerable amount of free water is present throughout lower snow-pack. Surface snow is a soft-slab formation.

Column Shear Test :
2 CT0 shears in upper pack at 13 & 20cm. Multiple easy shears in lower pack below 50cm. Compression of upper layers did strengthen them slightly, but they still failed on isolation.

Extended Column Shear Test :
Only partially carried out, but basically results of the shear test were replicated within the top layering.

Foot Pressure Tests :
Top 20cm would fail about 60cm from edge.

Rutschblock Test :
Not performed.

Activity Assessment :
Storm-slab is definitely present on E & W aspects above 1500m. At lower altitudes it is about 20cm, at 1800m it appears to be 1m+. It would be reactive in steeper terrain (40º+), and on convex rolls & near edges. Face deloads on solar aspects were also very active, with multiple Class 1 sluffs, but the ocassional Class 2-2.5 did roll off, initiated as a point release from higher altitude (1800m -1900m). Conditions were best described as poor, and should be avoided.

Current Assessment :
High Alpine (1800m+) - Considerable
Alpine (1200m - 1800m) - Moderate
Sub-Alpine (Below 1200m) - No Rating

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