Northern San Juan
AvalancheAmy Pertuz · Mar 18, 2021 · Northern San Juan
Weather
Mostly sunny skies with light/variable winds and strong radiation in the morning made for the beginning of an intense warm up in the first half of the day. Cooler temps arrived unexpectedly around 1pm with a light breeze from the NW and increasing cloud cover into the afternoon, keeping the warm up from accelerating . A very nice day to be in the alpine.
Snowpack
Storm totals from the last week are highly varied across the RMP corridor and NSJ. The Sneffels range has up to 60cm of settled storm snow, with the southern part of RMP holding closer to 40cm. On many SW-S-E aspects, a thin crust formed on Monday 3/15 was topped with a few more inches of new snow. This near surface crust was what many shallow, loose-wet slides on these aspects appeared to be running on, though occasional wet-loose slides that entrained more of the week’s storm snow were seen. Slopes facing SW-S-E had moistened surfaces, drainage runnels, loose-wet slides, and roller balls at rock bands and lower elevations, and wet-loose problems into the higher elevations.. High elevation E aspects had very little sign of loose activity and high elevation W aspects had none at all. Aspects with a hint of North (NW-N-NE) held onto cold surface snow even down to protected BTL slopes, and we did not encounter moist snow on these. On a NW aspect near TL, we found a HS of 185cm and a thin facet layer from 3/9 68cm deep. This layer produced hard results in compression and did not propagate in ECT, and was sandwiched between relatively soft 4F+ layers.
Avalanche
Many small wet loose on SW-S-E aspects, especially near rock bands. Lots of ski testing out there, only one slab was seen anywhere. This was in the Sneffels Range on a steep NE aspect ATL below a cliff band where recent SW winds appeared to have wind loaded this terrain, and failed under recent storm snow, likely mid week. SS-N-R2-D1.5-i, NE ATL. We experienced no signs of instability.