Aspen
AvalancheJason Konigsberg · Jan 30, 2020 · Aspen
Weather
On Monday it snowed most of the day and was very blustery. It was hard to measure snow at our near treeline location but I estimate 4 to 6 inches of snow. Tuesday was bluebird with cool northerly winds at ridgetop and no snow transport. Another inch or two fell overnight Tuesday with calmer winds. Wednesday was cool and cloudy with light wind and no snow transport.
Snowpack
Overall we observed very few signs of instability. No deep cracking or collapsing observed. The most significant event was the avalanche reported from Express Creek. I think this avalanche shows that although signs of instability are limited, this snowpack is incapable of supporting a large and rapid load. These continued small loading events are not producing many natural avalanches but large, very isolated ones. I thought we would have seen more activity with Monday's storm as we found wind drifts 1 to 2 feet deep on the following day. I think the lack of activity shows the decreasing sensitivity of our upper PWLs. As these heal, yet loading continues, our attention turns back to the monster in the basement which is our basal facets and depth hoar.---I dug on several south and north near treeline slopes and generally found the upper snowpack persistent weak layers to be unreactive. No propagation in extended column tests, and as stated above, no avalanches (except for one) with a not insignificant load on Monday.---Basal weak layers exist on most slopes regardless of aspect. The weakest, most worrisome basal weak layer I found was on a near treeline, southeast-facing slope. I think will continue to see isolated larger Persistent Slab avalanches with every loading event. A multi-day loading event would crush the snowpack and I think we would see a notable avalanche cycle.
Avalanche
Over the four days we observed very few avalanches. On Sunday (1/26), we observed an avalanche near the top of Express Creek ([previously reported) that was deep but relatively small to the path. When we came out on Wednesday, we saw that a much larger avalanche released from the same area. This is a heavily wind loaded area and parts of the crown are estimated at over 10 feet thick. The avalanche broke about 300 to 500 feet wide but only ran a few hundred feet. It is a though that this slide released on a snowy and windy Monday (1/27).