Southern San Juan
Snowpackmarkus beck · Jan 3, 2013 · Southern San Juan
Weather
Temp-inversion (Pagosa Springs was significantly colder than WCP). Clear cold night followed by clear skies and cool temps and mod radiation - widespread surface/near surface faceting observed (including 7-10mm surface hoar). Calm to very light winds though light SW'ly at ridge tops but barely any windloading observed. 2nd day past storm that dropped almost 2ft at Wolf Creek Pass.
Snowpack
Variable and still on the shallow side despite recent storms resulting in 3-4ft over the last 2 weeks. Latest storm dropped almost 2ft light density snow with no/little wind and decreasing temps. Compaction, sun, light winds are starting to settle the very light storm snow. Widespread surface faceting has set in. 1) Shaded slopes have weak foundation consisting of large dh (F hardness) under P to 4F faceting df's with a layer of buried very small sfc facets about 1/3 down (patchy) and 1-2ft of F new snow. A hand profile and CT revealed easy/clean failure on buried sfc facets and moderate/clean failure on dh. Many steep slopes approaching 40dgr have avalanched during the past two storms most of them running on dh. These avalanches are partially to fully refilled (spx tests on refilled start zones seem to indicate greater stability compared to similar slopes that have not avalanched). Shaded slopes 35dgr and steeper that have not slid are suspect for human triggering especially if wind loaded. --> see pictures. 2) Sun exposed slopes have a thin spx (avg. 1-2ft), small dh grains form a 1cm F layer, under P to 4F faceting df's with a 1-3cm thick faceting sun crust and 1-2ft of F new snow on top. I observed 3 collapses on a WSW slope (ranging 25-38dgr) that was moderately wind loaded, one of those ran approx. 80ft knocking off snow from trees. A test profile on a SSE 30dgr slope at 11,300ft with Hs 80cm produced CT10&11 Q1(sp) and ECT11(sp) on a layer of very small buried sfc facets 30cm down and CT23 Q1(sc) and ECT14(sc) on the 1cm basal layer of dh. I was unable to initiate failures on test slopes and stomping on trigger points. Sun exposed slopes approaching 40dgr with a Hs of at least 3ft are suspect to human triggering. --> see pictures.