Trip Planning for Dillon Area

Snowmobiled to lower rock island lake and ascended to 9200ft. Mostly sunny skies with no wind. No avalanches observed, no collapsing, minor cracking right around skis in wind affected areas 4 inches deep. Dug on due N aspect. HS = 120-150 cm. Soft surface 4-6 inches. 1 finger hard layers with rounding facets in between with 2 layers of concern about 1 foot down and 1 foot off the ground where 4F rounded facets are sandwiched between harder layers. CT6 Q2 down 4 inches on old snow surface. CT 23 Q3 on basal facets. ECTN 6 4 inches down, ECTN 29 about 1 foot down (consistent with last weekend observation in this area). Stubborn old snowpack right now with lack of significant new snow or wind and recent warm temps. Still poor structure in areas where snowpack is thinner, however where it is deeper seems facets are healing.

Snowmobiled to 8200ft then skied up to 9000ft. Dug a snow profile to ground on NE aspect at 8800ft. Height of Snow was 120cm (4 feet). Multiple weak layers in the snowpack including one about a foot down and a thicker layer of faceted sugary snow in the bottom 2 feet of the snowpack near the ground. ECTN29 on a crust and small grained facets about a foot down from the surface, however that slab layer released when a shovel was put behind it with a sudden pop and very little friction, see grainy photo. Surface was faceting old powder which could be another weak layer when buried. Not very reactive in this spot at the moment likely due to lack of new snow in a while. However generally poor snowpack structure is not reassuring and will need to watch when this snowpack gets rapidly loaded by new snow or wind blown snow. 

36” total. 24” sugar on bottom. 

From Email: It was actually great riding up there. Just no base once you broke through. Definitely solid on top and held weight of the sled. 

Snowpack at 8000 ft in pioneers is about 2 feet deep and mostly facets. About a foot of 3 mm large squares on the ground, a slightly more dense 4F- layer of crust and facets and another foot on top of that of soft NSF and new snow. Intentionally triggered a very small test slope, slab failed on the lower facet layer. See pics of quick pit and test slope results. Boot and ski penetration to the ground. Weak.

Early season snow recon outside of Maverick Mountain Ski Area boundary. Cracking of surface slab on easterly aspect at 8000 ft (see pics). Well developed weak layer about mid-pack that formed during November. Several storms the first week of December put down a 1-2 foot slab on top of this weak layer. Cohesiveness of slab varies by aspect and elevation. Wind and sun exposed slopes more reactive due to higher slab density. Areas protected from wind were not as reactive with no cracking experienced. Spatial variability is high with a shallow snowpack. See picture of quick pit showing major layering on north facing aspect at 8400 ft. Height of snow between 65-75 cm. Notable results were CTM 11 with a sudden collapse fracture character at 35cm up from the ground at November/December snow interface. ECTN 11 on same layer. The slab was not stiff enough in this protected location to propagate however this pit is representative of poor structure that is widespread. 

Also, snowmobilers reported avalanches on some of the steep roadcuts on the Pioneer Scenic Byway.