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Observations

Region: Summit
Location: Fresno Ridge
Observer:
Date:

Route & General Observations

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.

Red Flags

Obvious signs of instability

Recent Avalanches?NoCollapsing (Whumphing)?YesCracking (Shooting cracks)?No

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

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 Characteristics

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.

Photos & Video

Photos



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