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Avalanche Assessment Data Sheet

Archived Reports   (Opens a PDF file)

Click Here for current Temple Basin Avalanche Assessment information

Assessment Date & Time: 15/08/2017 1210hrs
Observer Name/s: CB + GK
Assessment Location: Upper Otira Valley - TL Flank   Altitude (m): 1555m
Slope Angle (xº) & Aspect (1-360º Mag.): 35º, 290º

Current Weather Conditions: Snowing, strong winds, poor visibility
Air Temperature (ºC): 8ºC
Wind Direction / Strength (1-360º Mag. / Kmph): 180º @ 25km/h
Hygrometer RH (%): 70% Rising
Uncorrected Barometer (mb): 918mb Falling

Previous Activity: Class 1 - 3 Otira Face deloads (storm activity)
Current Activity: Class 1 powder snow releases from Otira Face

Snow Crystal Descriptor Codes

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

Hardness Descriptor Codes (Hand Test)

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

Snow Structure Data

Temp
Gradient
Surface10cm 20cm30cm40cm 50cm60cm70cm 80cm90cm100cm110cm120cm130cm
0.7ºC -0.1ºC -0.2ºC -0.3ºC -0.2ºC -0.2ºC -0.2ºC -0.2ºC -0.2ºC -0.1ºC -0.1ºC -0.1ºC -0.1ºC -0.1ºC
140cm150cm 160cm170cm180cm 190cm200cm210cm 220cm230cm240cm250cm260cm270cm
-0.1ºC -0.1ºC -0.1ºC -0.2ºC -0.2ºC -0.2ºC -0.2ºC -0.2ºC -0.2ºC          
Layer Thickness
cm
(base)
Hardness
(Hand Test)
Xtal.
Size (mm)
Xtal.
Shape
Internal
Bond
Column
Shear
Force
ECT
Shear
Force
Density
kg/m3
Water
Equiv.
Notes
1 1 VH 3.0 F Good CTX 300 3mm Wind crust
2 14.0
(15)
S 1.0 C Good CTX 120 17mm  
3 19.0
(34)
S 1.0 C Good CT13 140 27mm  
4 11.0
(45)
MH 1.0 C OK CT5 200 22mm  
5 10.0
(55)
MH 1.5 P OK CTX 400 40mm  
6 8.0
(63)
MH 1.0 P OK CT23 360 29mm  
7 14.0
(77)
VS 2.0 P Poor CT24 480 67mm  
8 9.0
(86)
S 1.0 P OK CTX 360 32mm  
9 9.0
(95)
S 0.8-1.0 C Good CT4 420 38mm Free water present
10 33.0
(128)
VS 2.3 P OK CT15 440 145mm Free water present
11 2.0
(130)
VH 2.3 L Poor CTX 496 10mm Free water present, rain crust
12 6.0
(136)
VS 3.0 P Poor CTX 480 29mm Free water present
13 6.0
(142)
MH 1.8 P OK CTX 400 24mm  
14 38.0
(180)
S 2.0 P Poor CTX 520 198mm Free water present
15 16.0
(196)
MH 1.8 P Poor CTX 530 85mm  
16 8.0
(204)
MH 1.5 P OK CTX 520 42mm  
17 6.0
(210)
VH 3.0 M Poor CTX 450 27mm Free water present
18 5.0
(215)
VH 2.2 M OK CTX 450 23mm 0cm to rock
Pack Statistics
Snowpack Depth: 215.0cm
Snowpack Weight: 856kg/sq.m

Pack Analysis :
Completely isothermic pack. The new snowpack is quite obvious as early ET to 95cm, the original snowpack is very sugary and wet to base; definitely a rain affected snowpack at this altitude.

Column Shear Test :
Tests revealed a moderate (CT13) at 34cm, and an easy (CT5) 45cm, both presenting as a wind slab formation. Further more difficult shears were at 63 & 77cm. There was an easy/moderate (CT4, CT15) shear on the rain-crust at 130cm, however much of the column above was removed and it seemed quite stable within a non-compromised pack.

Extended Column Shear Test :
Not performed as weather atrocious.

Foot Pressure Tests :
No failure with foot pressure tests. We skied & snow-shoed our way up to, and away from this pit site through relatively steep terrain and failed to shed or fail any layering.

Rutschblock Test :
No performed.

Activity Assessment :
At this pit the avalanche risk could be rated as Moderate, though the overall pack presented quite stable (when not compromised), but certainly there was scope for surface slab releases in steeper, non-uniform terrain or on convex rolls. We skied and snow-shoed off with no effect. Less rain affected snowpack at higher altitudes certainly would present much less stable and a colder more fragile storm/wind slab formation that could certainly be triggered by skier/climber activity.

Current Assessment :
High Alpine (2000m+) - Considerable
Alpine (1000m - 2000m) - Moderate
Sub-Alpine (Below 1000m) - Low
 

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