We returned to the area between Mt Troy and Showboat today in search of gentler slopes and lower risk, given the unstable snow, and to search for uniformly weak but small test slopes to do AK Block size testing on while the snowpack is in the test value range we need more data on.

We found more sensitive snow than we did yesterday, even though the overnight loading was less than expected and the winds were light. It seems that the slab layers of new snow are gaining strength as they settle, allowing them to form a more cohesive slab that propagates fracture farther and more energetically than it did yesterday. The total load is also growing.

There were numerous whoompfs and shooting cracks on the way up, even on relatively flat slopes. The signs of instability were so strong that we did our tests right at the edge of the steeper open slope, nearly under the trees.

Both the AK Block and Ruschblock fractured as our tester began to step onto them, at a very weak #2 Quality 1 (clean and fast) on 40°. We attempted to move farther out onto the slope to do a series of block pairs of varying sizes as part of our AK Block research project, but as we began to excavate the first block, it whoompfed and cracks shot across the slope above it, fracturing visibly at the 34 and 45 cm layers.

We did a quick series of slab tests on it and then moved to lower slope angles to run our tests with less risk. The slab tests ripped clean and fast beyond the undermined area, #1 on our sensitivity scale, on both weak layers.

Our AK Block test pairs showed good correspondence between increasing block sizes and higher test values, though each pair varied depending on the local spatial variability of the snowpack. We noted that the lowest test values occurred where the slab was strong enough to support the tester's skis, in contrast to the softer slabs where the tester sank through immediately and was essentially jumping on the bed surface. This penetration factor is always a limitation of large block tests.

We rode down cautiously, keeping our slope angles under 35°. It was hard to keep planing in the dry but dense new snow. The crystal types have been small, and many are broken or rimed, causing the high 190 Kg/m3 density despite light winds and low temperatures.

It should be noted that we tested on slopes where facets and surface hoar underlie the new snow. In areas exposed to the recent clear weather winds, these layers have been eroded right down to the December 23 to 24 thaw crust. The bond there is likely to be stronger, but still weak, especially due to the faceted and variable nature of the melt freeze crust. Despite the stronger bond, the slabs there are likely to be more continuous and sensitive today, just as we found in our area.

Loading is continuing this evening and forecast to continue, with warming late in the week. Any rapid loading, wind loading, or rise in temperatures could tip the balance now. The bed surfaces are fast and have low friction, and there is snow to sea level, so slides could reach lower elevations, especially from high elevation starting zones with bowls that catch drifting snow. Flatter starting zones may require more snow to produce large slides to low elevations, perhaps closer to a meter, rather than the half meter we have now.

The Juneau area mainland paths should not be trusted, and the backcountry should be considered treacherous. Travel only on low slope angles and stay out from under large paths. Watch for the increasing snowfall, windloading, or rising temperatures that are the likely precursors of a natural avalanche cycle.

Hikers at Eaglecrest should beware tomorrow, the ski area plans explosive avalanche work for most of the day. Be sure to stay out of the areas they are working in.