Aspen

The avalanche occurred on a northwest-facing slope above treeline on January 14, 2026, sometime between 10:00 and 12:00. It was medium relative to the path and large enough to bury and destroy a car, break a few trees, or destroy a wood-framed house (R3-D3). Debris filled the creek below the path and ran up the opposite bank, with parts of the debris pile at least 60 feet deep. The crown face ranged from around 40cm to over 110cm. The avalanche broke on facets and depth hoar at the ground. Several small to large rocks were found in the debris pile along with many small trees and shrubs. What makes this such an interesting avalanche is that it released naturally during a quiet period, while all signs were pointing to conditions quickly becoming more stable, and it surprised several avalanche forecasters and long-term residents of the area. A near-record-breaking low-snow year with unusually warm temperatures has defined most of the season to date. Notable wind events in mid-December stripped much of the season's snowpack off this particular slope, keeping it notably more shallow than adjacent slopes. Images of "The Shield" in late December and early January highlight how unusually shallow the snowpack was, as you could easily see small bumps in the terrain with plenty of shrubs still poking out of the snow. December brought a long dry spell with rain on Christmas Day (December 25) reaching elevations up to 11,000 feet and depositing a few inches of dense snow above that. Early January storms (January 1-9) brought about 3 feet of snow to the area, with the tail-end of these storms depositing notably low-density snow. In the two weeks prior to the avalanche (January 1-14), 191 avalanches were documented, with the vast majority being small, soft slab avalanches confined to the new snow. Only 12 avalanches were larger than D2 (ten D2.5 and two D3), and they all occurred on January 2 or January 5, including this notable D3 avalanche in North Anthracite Creek that propagated over a mile wide across multiple slopes: https://avalanche.state.co.us/report/836cfb04-0413-47c6-8877-326202546c7a. Avalanche activity dramatically tapered off in the days prior to the avalanche (January 9-14), with most of the avalanches reported being Loose Wet avalanches on south-facing slopes on January 12 and 13. The winds over the previous 2 days were notably light and from the north, which would most likely have been scouring this slope rather than loading it if the winds were moving much snow at all. A lack of cornice growth along the ridgeline, which often has large cornices, and several reports of individuals traveling in Yule Creek and observing no wind, even on Treasure Mountain, which typically sees snow transport even on relatively calm days, support this. There were no wildlife tracks anywhere near the avalanche, ruling out the possibility that an animal triggered it. It also seems unlikely that it was rapid settlement from the storm snow as that occurred several days earlier (see SNOTEL data). Although we will never know with absolute certainty, most of the evidence points to this avalanche being caused by liquid water in the snowpack reaching the weak layer near the ground. The area saw unusually warm temperatures the previous 2 days, with the nearby Schofield SNOTEL station at 10,700 feet recording above freezing temperatures on January 12, 13, and 14. The nearby North Lost Trail SNOTEL station at 9200 ft. recorded high temperatures in the high 30s to low 40s on January 12 and 13 and reached above freezing temperatures before noon on January 14. The previous several days were also clear and sunny. CAIC staff conducting fieldwork nearby in Capitol Creek on January 12 noted abundant snow melting off the trees, introducing water into the snowpack on north-facing slopes. Untouched snow adjacent to the avalanche path, on the more west-northwest-facing side of the avalanche path, had a notable melt-freeze crust on the snow surface and clear evidence of liquid water entering the snowpack around trees and rocks up to 11,300 feet. This path also has large cliff bands along the “lookers” right side of the avalanche path that face southwest. The warm temperatures, a slab thick enough to insulate the snowpack from overnight freezes, a snowpack relatively thin compared to nearby slopes, and an abundance of thermal bodies such as trees, shrubs, and rocks around and in the avalanche path all likely contributed to liquid water being the main cause of the avalanche. Again, we will never know for sure, but given what I observed, the weather patterns at the time, and several long discussions with peers and coworkers, my best guess is that this was a Wet Slab avalanche.

Warm, sunny day with a light breeze and some noticeable snow transport along Treasure Mountain, but nowhere else that I saw.

Snow surfaces are mostly either melt-freeze crusts on south-facing slopes near and below treeline or a thick (10-20cm) layer of near-surface facets on more north-facing slopes. There were isolated patch of wind-drifted snow where I could get some cracking in the snow but these were sporadic and small.