| Recent Avalanches? | No |
| Collapsing (Whumphing)? | Yes |
| Cracking (Shooting cracks)? | No |
Observation: Summit
Location: Fresno Ridge
Toured from MP49 pullout to 2800′. Thin conditions persist in the Summit area, but overall it was a warm, calm day for a nice tour in the sunshine. Of note – wind crusts that were previously supportable have faceted just enough to be breakable now, making for challenging skiing below about 2400′. Also of note – the sun is now affecting the snow on steep, solar aspects.
Obvious signs of instability
Observer Comments
Got a subtle whumph at 2800' in a wind loaded area. Dug a quick pit to investigate, see below for pit results.
Weather
Strong inversion, and wide diurnal temperature swings: -2 degrees F at 1030 at the truck, then 22 degrees F at 1500 at the truck. Downright hot skinning in the sun at upper elevations. Calm wind, clear skies.
Snow surface
2" of new snow from 2/6 sits atop widespread buried surface hoar (BSH) at all elevations. There is new surface hoar growing at all elevations, increasing in size with elevation, from small 2-3mm wedges at 1400 to 6mm feathers at 2400'. There is evidence of recent wind below the 2/6 snow, in the form of old tracks filled in with stiff, wind-compacted snow, and thin breakable wind slabs in exposed, previously wind affected areas.
On steep, solar aspects a thin sun crust can be found (see photos).
Snowpack
Our goal was to get a feel for the reactivity of the 1/25 BSH, and the crust-facet-crust sandwich (CFCS) from December / January storms.
At 1475' hand pits failed on isolation on facets below the 1/15 rain crust. The 1/15 crust becomes thin and deteriorated with elevation, and by 1800' the 1/15 rain crust is a thin (2mm) translucent lens. By 2400' the 1/15 rain crust can only be found spuriously. The Dec/Jan CFCS becomes more deteriorated, and the facets between and below crusts are very loose.
Several layers of BSH can be found intact: 2/5, 1/25, 1/11, 1/1. A "whumph" was felt at 2800', and the 1/25 BSH or 1/11 is believed to be the culprit. A pit was dug at this location, and the 1/25 BSH was found intact 65cm below a pencil hard wind slab. An ECT showed propagation at this location (ECTP14) on this layer. It is worth noting that depths were highly spatially variable here, and ~15 meters away the snow was only 35 cm deep.
Two more pits were dug in a wind protected location ~200' lower, and the 1/25 BSH, CFCS, and 1/11 BSH were found intact. One pit showed propagation in the 1/11 BSH, and the other showed no propagation, due to the lack of a slab.
Old tracks were filled by wind prior to the 2/6 new snow.
Pronounced cross-loading on Moose
Cross-loading and a thin snowpack on north aspects of Colorado
Manitoba as seen from Fresno Ridge. Some wind effect can be seen near ridgelines.
Sun crust forming on steep, solar aspects
Hand pit at 1475'. Note the buried surface hoar intact below 2" of new snow and crust-facet sandwiches.
Quick pit at 2400'. The 1/15 rain crust cannot be found here. Several layers of buried surface hoar and crust-facet sandwiches can be found.
Pit at 2660'. ECTP19 on 1/11 BSH. CT failures at various weak layers found in snowpack. HS=86cm.
Pit 2800 ft