THIS SNOWPACK SUMMARY EXPIRED ON December 12, 2014 @ 11:56 pmSnowpack Summary published on December 12, 2014 @ 5:56 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Wet Slab
Wet Slab avalanches occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoid avalanche terrain when you see pinwheels, roller balls, loose wet avalanches, or during rain-on-snow events.
Recent warm/wet weather has modified our once loose/dry surface snow into a wet slab. This wet layer is adhering quite well to the November 27-28 rain crust below it. Extended Column tests did not propagate a fracture at this interface.
Avalanche Character 2: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.
Below the November 27-28 raincrust is a persistent slab that extends to near the ground surface. At the snowpack - beargrass interface is a thin layer of loose/dry snow composed of large angular grains. Using the Extended Column Test, the 3 foot wide by 1 foot deep column failed with 3 elbow strikes and propagated across the whole column at the ground interface.
Snow depths throughout the Kootenai Region are lacking.
Little to no off road riding is ocurring with snowmobiles. Some snowboarding at upper elevations is being done by people hardy enough to get there.
Backcountry travelers are urged to use caution when navigating open unanchored slopes at elevations above 6500 feet.
Today I visited the east aspect of Rattle Mountain 6038 feet elevation located in the West Cabinet Range.
There I found a 5 inch rain saturated surface layer. The near surface snow of 3 inches was 1 finger hardness and the bottom 2 inches was 4 finger hardness. These layer sit atop the November 27-28 rain crust which has softened to a pencil hardness with recent warm and wet weather. Approximately 10% of your boot steps will now penetrate this softened rain crust. The bottom 4 inches of the 25 inch snow column is 1 finger hardness with the snow - ground interface being quite loose.
Weather and CURRENT CONDITIONS
Since Monday, Kootenai region weather has been warm with all stations above freezing to 40ºF and wet. Only high elevations received snow. Otherwise all stations showed SWE gains as rain. Overall drain from the snowpack was on the order of -0.2 inches. Weather Thursday at 6000 feet was 38ºF, calm winds, overcast with light rain. Forecasted weather through Friday is mostly cloudy with above freezing temperatures day and night. South winds at 10-17 mph with gusts to 35 mph will NOT transport snow as it is wet from recent rain events. High chance (40-80%) of more light rain with the snow line well above 6000 feet elevation.
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
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