Northern San Juan
AvalancheColin Mitchell · Mar 18, 2021 · Northern San Juan
Weather
A warm day with light winds and lots of radiation. High thin clouds moved in and out through the day with a few thicker layers interspersed.
Snowpack
I traveled on south and southeast aspects today near treeline. HS averaged around 170 cm, but I targeted a thinner area with my profile. Recent snows have settled out to a foot thick layer of 4f-hard moist, rounding grains. A thin crust had formed on the surface overnight and was breaking down in the afternoon sun. The new snow layer sits over a melt-freeze crust formed during our last warm-up earlier this month. Below this are several layers of rounding facets and depth hoar interspersed with a few crusts and ice masses. Although still recognizable as faceted grains, a lot of rounding has occurred in these layers and they have strengthened to 1f to K-hard. ECT tests targeting the crust at the recent snow/old snow interface produced non-propagating results- ECTN 16 and 18. Right below this crust, I found perc columns and ice masses down about 20 cm or so, indicating some free water was entering the snowpack during our last warm spell. The upper few centimeters of the snowpack was wet by 12:30 pm, and some runnels were forming at the surface on steep sunny slopes by 2:00 pm, both indicating some meltwater was beginning to percolate down into the new snow.
Avalanche
No new activity of any kind observed today.