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Observation: Summit

Location: Fresno Ridge

Date:
Observer:
Route & General Observations

Ascended and descended Fresno Ridge to 2750′. Our goals were to a) inventory surfaces in preparation for new snow b) characterize the extent of the persistent slab problem c) understand the structure of the snow on the windward side of the road d) understand the the extent and depth of the melt freeze crust near the surface (will the MFC act as a good bed surface for the new snow?)

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Observer Comments

No red flags observed.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

0930: 1200' - 5F, calm, no precip, scattered clouds
1245: 2746' - 18F, calm, no precip, few clouds
1400: 1200' - 4F, calm, no precip, scattered clouds

Snow surface

All elevation bands had surface hoar increasing in size and changing shape from 5-6 mm wedges near the road at 1200' to 10-20 mm feathers and wedges at 2700'. The surface hoar perched atop near surface facets that ranged in size from 1.5 mm at 1300' to 0.5 mm at 2750'. The thickness and distribution of the near surface facets was quite variable, ranging from 1 cm thick to 10 cm thick. Underlying these near surface facets were either two stout surfaces that will make good bed surfaces - a stout melt freeze crust or wind slab ranging from breakable to "slide for life."

Above 2750' surface hoar glittered in our near vision above but was not as easily discernible on ridgetops. Above treeline along the ridge, slopes were either scoured down to a thin melt freeze crust or loaded with wind slabs.

Snowpack

The snowpack structure generally consisted of surface hoar on top of near surface facets over a combination of wind slabs and melt freeze crusts over the Thanksgiving facets over basal ice to ground. What is particularly notable is how widespread the melt freeze crust is and how effective it has been at laying over grass and making a pretty thin snowpack skiable.

Snow depths were quite variable depending on scouring and loading from wind:
1300': 30 cm
2000': 55-75 cm
2700': 60-80 cm

We dug two pits near our high point at 2750' looking for thinner "trigger points" in our snowpack in areas that did not harbor obvious stout melt freeze crusts in our probing. Pit profiles in pictures below. In certain locations we found that you can find a hard slab, sitting over a moderate to high strength weak layer, on top of a slick bed surface that may have propagation potential.

Photos & Video
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