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| Juneau Area Avalanche Advisory | ||||||||||||||
| 2006-01-03 | ||||||||||||||
| Mt. Stewart | ||||||||||||||
| by Bill Glude, SAAC Observer | ||||||||||||||
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| We did fieldwork on Mt. Stewart again today, encouraged by fresh snow hanging on the trees down to 200m. Down low, the snow was moist and only about 5cm thick. On the higher slopes, it was up to 10cm thick and drier. Combined with earlier snow, there is now up to 20cm of soft snow on top of the December 29 rime crust.
The only signs of instability we observed were cracking in drifted areas. The drifts were localized and most slopes, even those showing windloaded texture, scored low-energy #3-4 (less than half the undermined area, irregular) Slab Test ratings. Our block tests had some low values though. All three non-cutback blocks fractured fairly easily on the 175cm rime crust at #2 (on stepping onto the block) to #4 (first gentle jump). All five of our blocks fractured on the deeper 153cm Solstice thaw crust at strong values, all at #6 except one that went at #4. All shears were average #2 quality on 41°. We rated the strength -, the stress ~ to + (depending on windloading), the energy +, and the structure -, where + indicates a strong snowpack, - weak, and ~ neutral. Despite some weak structure and shears, the slab did not transmit energy well and was not critically loaded. It is of interest that the layer right above the Solstice crust was early facets, and the top of the crust was faceted melt-freeze. Both tend to be persistent and unpredictable weak layers. Watch for windloaded areas and for the next snow and wind event. We have a setup for instability if it is loaded rapidly or heavily. Large avalanches reaching low elevations are unlikely unless it really loads heavily and rapidly, but a cycle is likely. |
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| Field Notes | ||||||||||||||
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| Photos | ||||||||||||||
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| Andy Dietrick shears an AK Block sized for his weight on the 175cm rime crust from December 29 at average shear quality as he steps onto it (AK2Q2) on the 41° slope. This layer fractured first in all our non-cutback test blocks, but was not detected by either of our two cutback blocks. This block had the easiest shear on this shallow layer. The others all went on the first gentle jump, or #4. | ||||||||||||||
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| Andy Dietrick shears the same AK Block on the deeper 153cm thaw crust from the Solstice thaw at average shear quality on multiple hard jumps (AK6Q2) on the 41° slope. This layer fractured in all our test blocks. All went on multiple hard jumps, #6, except for the Cutback AK Block, which went on the first gentle jump, #4. | ||||||||||||||
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| Sun breaking through clouds above drifting fog made for spectacular late afternoon light. | ||||||||||||||
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| Today was by far the most wintry-looking field day in this warmest-ever season and it also had the best snow, but the thin and brushy spots are visible even in this distant view of Eaglecrest. Riding requires caution, knowledge of where every rock is, and a long climb to high elevation. Two of our crew tried Cropley Chute, and left sacrificial offerings of P-Tex ski base material on the rocks there for the snow gods. | ||||||||||||||
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| Sun spotlights the ridges above upper Fish Creek and part of Mt. Juneau. While some high slopes are smooth, the brush and rocks reveal thin snow up to at least 650m. | ||||||||||||||
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| Marc Scholten finds good snow in sunset light high on the mountain. | ||||||||||||||
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