Southern San Juan

Avalanche

Chris Bilbrey · Apr 5, 2022 · Southern San Juan

Weather

Overcast skies in the morning with very light (S-1) snow flurries. Skies began to break apart midday giving way to partly cloudy skies by 3 pm. The wind was consistent throughout the day out of the west-southwest transporting recent snowfall onto easterly slopes. Wind loading broader above treeline, although visible surface texture from the wind observed as we approached treeline.

Snowpack

We observed a lot of variability in the snow surfaces between 10,500 and 11,000 feet. Large openings on treed slopes and meadows had a 6 to 8 inch refrozen surface with minimal boot penetration. As vegetation increased on slopes or those more heavily treed, the refrozen surface was shallower (3 to 5 inches) and boot penetration ranged from 8 inches to full depth. Below 11,000 feet, northerly slopes remain the most supportive and meltwater continues to work its way toward the base of the snowpack. All other aspects have transitioned to a spring, isothermal snowpack or melting quick. Due north slopes continue to fight the transition to a spring snowpack below treeline. Drifting of recent snowfall was the main driver of elevated hazard in this area today. The wind was strong enough to erode a thin surface crust on westerly slopes and effectively transport snow onto easterly slopes. Northwest and north slopes were being cross-loaded, but fresh slabs there were stubborn to ski pressure. At times of strong gust along ridgelines, we observed surface sluffing in drifted snow below cornices on easterly slopes. Sluffing did not contributed to large, broad slab failure. Taking a few steps down a wind-loaded pocket produced minor cracking at our feet and newly formed slabs were soft (1F- to 4F). Digging on north-northwest slope at treeline revealed similar findings to other parts of the South San Juan. A deep, stout slab sitting above the primary layer of concern. The 2/21 interface, aka "drought facets", are 1F-, rounding, and were unreactive in Extended Column Test. As we move further into spring, it seems less likely that a rider or machine could impact these weaker grains buried around a meter below the surface. The overlying slab seems to be winning the battle against weak layer weakness without a major loading event or heavy rain-on-snow.

Avalanche

No fresh avalanches, but we observed natural sluffing below cornices during stronger gusts creating eddy swirls of snow.