| Trigger | Natural | Remote Trigger | No |
| Avalanche Type | Unknown | Aspect | Southwest |
| Elevation | 3700ft | Slope Angle | unknown |
| Crown Depth | unknown | Width | unknown |
| Vertical Run | unknown |
Avalanche: Turnagain
Location: Sunburst
Normal uptrack to about 2700′. We dug a couple pits along the way to check how the new snow was bonding to the old surface. At 2200′ the new snow showed signs that it was not bonding well to the old surface. There was about 1.5-2′ of new snow that failed on the old surface and propagated across the column in our test (ECT P 23). At upper elevations there was widespread wind loading and we saw one recent natural avalanche that had released on a wind loaded slope.
Avalanche Details
We saw a recent avalanche in one of the upper start zones on Sunburst at around 3700'. It looked like a fresh wind slab, but it is possible that it released during the storm. We only saw it from far away, but I would guess it was 1-2' deep and 100' wide. There was some debris in the gully below, but we did not have a good angle to see how far down slope it ran.
Weather
Broken cloud cover in the morning with more clouds moving in towards afternoon and light snow showers. It was lightly raining below 300' on our drive back to Girdwood at 3 pm. In the morning there were moderate winds at ridgetop elevations that were causing an impressive amount of snow transport.
Snow surface
Below about 1400' we found a breakable ice crust on the surface. Above that there was 1.5-2' of new snow. Above treeline the snow was more wind affected, but still soft.
Snowpack
At our first pit at 2200' the total snow depth was 220 cm (~7'). In this location there was about 30 cm (12") of soft snow on the surface with a 15 cm (6") layer of denser and more wind affected new snow underneath. We had a propagating failure in our extended column test below the 45 cm (18") of new snow at the interface with the old snow surface. This is a concerning results because the old snow surface was a layer of near surface facets, which have the potential to develop into a persistent weak layer if they were well preserved before the new snow fell.
Our upper pit at 2700' was much shallower, with a total depth of 140 cm (~4.5'). We did not find the layer of near surface facets underneath the new snow in this location. Likely because it is more exposed to upper elevation wind and therefore has a very different snowpack structure. We need more information to determine how widespread the layer of near surface facets that failed in our lower pit might be.
Snowpack structure at our lower pit.
Sun triggered roller balls in early January?!?!?
Breakable crust below 1300'
Lots of wind transport at upper elevations.
Storm interface where our test failed about 2' deep.
Large glide crack lurking under the Tincan Library.
Soft wind affected snow along Sunburst ridge.
Natural avalanche on Sunburst ridge