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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: 8/11/2016 1413hrs
Observer Name/s: C.Young, G.Kates
Assessment Location: Bealey Slide, Mt Rolleston (E1480013 N5248211)   Altitude (m): 1472m
Slope Angle (xº) & Aspect (1-360º Mag.): 35º, 195º

Current Weather Conditions: Fine, cloud over tops west, winds building
Air Temperature (ºC): 7.8ºC
Wind Direction / Strength (1-360º Mag. / Kmph): 270º @ 20km/h
Hygrometer RH (%): 75% Rising
Uncorrected Barometer (mb): 1007mb Stable

Previous Activity: Considerable avalanche debri from last storm-cycle visible up to Class 2 on north & east aspects.
Current Activity: Numerous Class 0.5 - 2.5 wet-snow point releases observed on north & east aspects, 1600-1700m, on 30º+ slopes.

Snow Crystal Descriptor Codes

ABCDEFGH
Fresh snow Irregular grains, mostly rounded, but often branched. Early ET Rounded, often elongated. Isometric grains. Late ET. Angular grains with flat sides or faces. Early TG. Angular grains with stepped faces; at least some hollow cups. Advanced TG. Rounded grains formed by MF metamorphism. Graupel. Ice layer, lens, or pockets.

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
0.4ºC 0.2ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.2ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC 0.1ºC
140cm150cm 160cm170cm180cm 190cm200cm210cm 220cm230cm240cm250cm260cm270cm
0.1ºC 0.1ºC                        
Layer Thickness
cm
(base)
Hardness
(Hand Test)
Xtal.
Size (mm)
Xtal.
Shape
Internal
Bond
Base
Shear
Force
Density
kg/m3
Water
Equiv.
Notes
1 8 VS 1.0-2.0 F Poor Very Easy 550 44mm Free water present, poor sintered bonds, wet snow - sugary
2 14.0
(22)
VS 1.0-2.0 F Poor Moderate 560 78mm Free water present, poor sintered bonds, wet snow - sugary
3 4.0
(26)
S 2.0 F Poor No Shear 680 27mm Free water present, poor sintered bonds, wet snow - sugary
4 3.0
(29)
S 1.0-2.5 F Poor No Shear 520 16mm Free water present, poor sintered bonds, wet snow - sugary
5 3.0
(32)
VH 1.0-2.0 F Poor No Shear 520 16mm Free water present, poor sintered bonds, wet snow - sugary
6 5.0
(37)
S 1.0-2.0 F Poor Moderate 520 26mm Free water present, shear uneven break, wet snow - sugary
7 18.0
(55)
S 2.0-3.0 F Poor Moderate 440 79mm Free water present, poor sintered bonds, wet snow - sugary
8 5.0
(60)
H 4.0 H Poor No Shear 560 28mm Free water present, poor sintered bonds, wet snow - sugary
9 18.0
(78)
MH 1.0-1.5 F Poor Hard 520 94mm Free water present, poor sintered bonds, wet snow - sugary
10 5.0
(83)
VH 1.0-2.0 F Poor No Shear 600 30mm Free water present, poor sintered bonds, wet snow - sugary
11 3.0
(86)
I 1.0 H OK No Shear 600 18mm  
12 10.0
(96)
VH 1.0-2.0 F Poor No Shear 560 56mm Free water present, poor sintered bonds, wet snow - sugary
13 3.0
(99)
VH 1.0-2.0 F Poor No Shear 480 14mm Free water present, poor sintered bonds, wet snow - sugary
14 3.0
(102)
VH 1.0-2.0 F Poor Hard 480 14mm Free water present, poor sintered bonds, wet snow - sugary
15 8.0
(110)
VH 1.0-2.0 F Poor No Shear 480 38mm Free water present, poor sintered bonds, wet snow - sugary
16 7.0
(117)
VH 1.0-1.5 F Poor No Shear 480 34mm Free water present, poor sintered bonds, wet snow - sugary
17 33.0
(150)
MH 1.0-1.5 F Poor No Shear 520 172mm Free water present, poor sintered bonds, wet snow - sugary
Pack Statistics
Snowpack Depth: 300.0cm
Snowpack Weight: Indeterminate!

Pack Analysis :
Snowpack is completely isothermal. There are two hardened, thin ice layers at 60 & 86cm, both of these would present a temporary barrier to moisture ingress and could create failure interfaces. Radiation today was continually "onion skinning" the surface pack leading to continuous natural wet slides initiating on high solar aspects at similar period intervals (20-30 minutes).

Shovel Shear Test :
Shear testing resulted in surface slush sliding off easily. Moderate shears were noted in the upper pack about layers where there was interface crystal size variation between the layers (sliding off on ball bearings). Harder shears were noted in the lower pack, though these were quite well bonded with similar underlying layers.

Compression & Foot Pressure Tests :
Foot compression test only really "pushed" off the top slush layer. Quite substantial force near pit edge did not fail any further layering.

Rutschblock Test :
Not performed, no skis.

Activity Assessment :
Given the amount of continuous active avalanche paths witnessed today in the full PM (1300 - 1700hrs) on solar aspects (up to Class 2.5 on ocassion), and the obvious effect of radiation penetration on the surface pack, the isothermal snowpack containing considerable free water and no sintered bonds - avalanche risk could be considered Considerable to High on aspects exposed to radiation for any length of time. Heavy rain to high level from tomorrow will further compromise the pack leading to a cycle of wet snow events.

Current Assessment :
High Alpine (2000m+) - Considerable
Alpine (1000m - 2000m) - Considerable
Sub-Alpine (Below 1000m) - No Rating
 

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