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Surface hoar in the Program Area
Location Name:
BNSF Avalanche Safety - Running Rabbit Mtn GNP
Observation date:
Monday, December 30, 2019 - 19:00
Is this an Avalanche Observation:
No
Observation made by:
Public
Tabs
Quick Observation
Toured through the upper elevations of Shed 10, Path 1163, and Shed 11 today
Objectives were to observe snowpack surface conditions prior to tomorrow’s forecasted snow, obtain some baseline data from Shed 10 and 1163, and re-do stability tests in Shed 11 at same location as the Dec 23rd snowpit.
A cloud deck of stratus clouds hung around all day from about 5000-7000 feet elevation. Skies were clear above this till late afternoon when some upper elevation clouds began moving in.
Winds were calm or light from the southwest and no precipitation all day.
Air temperatures were in the high-teens to low-20s °F above 6000 ft. elevation this afternoon and warmed to the mid-20s °F at the Canyon floor.
Below 5000 feet there is little to no snow on sunny slopes. In the shade snow depths range from 3-8 inches.
From 5000-6000 feet the snowpack gradually thickens to about 1-2 feet deep. It’s capped with a stout and usually supportable crust from last week’s warm-up. On top of the crust there’s an inch or two of near-surface facets topped with a new crop of surface hoar (5-10 mm).
From 6000-7400 the snowpack varies from 1-5 feet deep. Last week’s crust becomes breakable and pretty thin by 7200 feet, but still present on sunny aspects. Snow surface is composed of a few inches of near-surface facets and some impressive surface hoar (5-10 mm)
The Program Area has received only trace amounts of new snow over the past week.
One of the most notable observations today was the surface hoar growth. It’s widespread above 5000 feet elevation and found on all aspects. That and the faceted basal layers appear to be gaining some strength.
Dug a test pit in the upper reaches of Shed 10, 7030’, east aspect, 30° slope. Snow depth=62 inches with a poor snowpack structure consisting of a 1F-P hard slab sitting on top of a crust/facet/crust layer combo at the base (pit profile attached). No propagation with an Extended Column Test. A Deep Tap test on the bottom layers yielded DT22, BRK, 2 inches from the ground.
Second snowpit and full profile dug in the upper reaches of 1163, a steep, rocky, wind-affected location at 7260’, SE aspect, 38° slope. Snow depth=37 inches with a poor snowpack structure and the same crust/facet/crust sandwich at the base (pit profile attached). No propagation with an Extended Column Test. Sudden collapse in the layer of rounding depth hoar at the base of the snowpack, CT18 SC with a Compression Test.
Re-visited the site of our snowpit/profile from Dec 23rd in the Shed 11 path. Extended Column Test then yielded ECTP11 and ECTP13 on the basal facets. Today, ECTN25 on this same layer.
No avalanche activity observed.
Snowpack, Avalanche, Weather Images:
Travel Details
Region:
Flathead Range/Glacier National Park - John F. Stevens Canyon
Activity:
Skiing
Hiking
