Observation: Summit

Location: Birchtrees

Route & General Observations

APU Snow Science course tour to Birchtrees. We were on a look out for the persistent weak layers and to compare the snowpack between Turnagain and Summit zones.

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

In the beginning of the tour 10:30am at roadside scattered skies, calm wind, no precipitation, air temp -1.5C/29F.
At the top of the tour (elevation 2400') 2:30pm scattered skies, light wind from N, no precipitation, air temp -3.5C/26F

Snow surface

3-5mm surface hoar and near surface facets on the top of the snowpack.

Soft surface snow conditions were 10-15cm of recycled powder through the tour. We did not find any wind impacted surface snow.


Snowpack is still shallow at Summit, HS varied between 105-155cm.
We dug at two locations before skiing down the hero snow.

At the lower pit, 1700', E,, we found two distinct layers of buried surface hoar, 10cm and 25 cm from the top. BSH at 25cm was more reactive and showed propagation propensity (PST28/100End), even without very hard slab above it. We also practiced doing temperature profile and noted a very strong temperature gradient (4°C/10cm) at the top of the snowpack.

At the higher pit location, 2400', we dug on two separate spots. One of the pits had 15cm of windslab below the soft surface snow. Below the windslab we found a facet layer that showed some propagation propensity (PST60/100End). The other pit in close vicinity consisted of several layers of rounding facets at different hardnesses. It did not have the buried surface hoar layers and produced insignificant test results.

Photos & Video
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