Northern San Juan

Avalanche

Chris Bilbrey Ann Mellick · Mar 16, 2021 · Northern San Juan

Weather

Overcast skies mid-morning gave way to periods of S1-2 snowfall by early-afternoon. Accumulations were minimal and maybe amounted to an inch by 2:30 pm. Winds were light out of the south-southwest and moderate gust not contributing to any remarkable drifting.

Snowpack

Consistent snowfall since March 8 has built a generally right-side-up soft slab. We found generally good bonding between individual storm layers on wind-sheltered slopes near and below treeline. Sitting below the recent snowfall is a faceted crust on north to east aspects at higher elevations. This crust/ facet combo is buried around 50+ cm's deep and is the most concerning weak layer in the upper snowpack at present. It has become more reactive recently from the new snow load, but sensitivity varies within the forecast zone. We observed non-propagating results (ECTN 19) in our Extended Column Test in that same layer and moderate failures (Sudden Collapse) in our Compression Test. Our results suggest that finding the right slab/ weak layer combo still has potential to fail from the weight of a rider. This is more likely on slopes that are heavily wind loaded or where the overlying slab is deeper adding more stress or weight to weaker snow below. Plenty of alpine slopes are smoothed and look phat or heavily loaded. It is important to approach steep, wind-drifted slopes with extra caution while the upper snowpack settles. As the slab stiffens, it can become more susceptible to fail from a rider, especially during times of above freezing temperatures - as in the forecast over the coming days.

Avalanche

Pretty quiet out there in terms of new, recent avalanche activity. Cornices continue to grow in size and it'll be important to give these beasts a wide berth during our next major warmup.