THIS SNOWPACK SUMMARY EXPIRED ON February 25, 2015 @ 10:57 pmSnowpack Summary published on February 25, 2015 @ 5:57 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: 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.
The near surface melt-freeze crust complex continues to release with moderate force, but not propagate. Sub freezing temperatures since Friday appear to have stabilized the snowpack a bit. We are not observing the same level of failure propagation nor boot penetration. The rain crust from February 6th-7th appears to be universally "bomb proof". Deep slab weaknesses that we were tracking for weeks appears to be bridged over after this massive rain on snow event followed by deep freezing temperatures.
On this date a year ago at the very same location in Whoopee Basin, my pit records show that I was digging in a 94 inch snowpack (vs 45" today). SNOTEL records show that the West Cabinet Range is approaching 50% of annual average for Snow Water Equivalent. What a difference from a year ago! Today, to reach my destination, I crossed four significant stretches of terrain on solar slopes (south/west aspects) that were totally void of snow. Current snowpack conditions are mostly stable. No significant thawing or storm loading is forecasted. Enjoy good snow where you find it, BUT continue to use those proven practices and good decision making that has kept you safely on top.
Today I visited Whooppee Basin 6,000 feet elevation in the West Cabinet Range. There I encountered 45 inch snowpack on a steep east aspect. The top 8 inches is a combination of three knife hard layers with soft snow in between. These hard layers are not penetrated by snowmobile, ski or boot. Below these near surface hard layers is a 6 inch knife hard rain crust from February 6th-7th. This layer is nearly impossible to penetrate with an avalanche shovel. Below this crust are several pencil hard layers. At 4 inches from the ground surface the snow is loosely consolidated facets.
Extended Column Tests produced a fracture but no propagation with moderate force at 37 inches from the ground. (ECTN 15) Above this failure is the 8 inch sandwich of three knife hard crusts with soft snow between. A layer 4 inches from the ground propagated a fracture with hard force (ECTP 28 Q2) . Above this failure is 32 inches of pencil hard slab material.
Weather and CURRENT CONDITIONS
Since the Friday February 20th advisory, weather in the Kootenai Region has been cold and dry with a small pulse of snow Saturday morning. All SNOTEL sites have been reporting below freezing temperatures day and night till noon today. SNOTEL sites are reporting SWE increases of 0.5- 0.8 inch associated from the Saturday morning snow. Weather yesterday at Whoopee Basin in the West Cabinet Range was high thin clouds, calm winds, 30º F, and no new snow. Forecasted weather through Wednesday is for increasing cloud cover (55-70%), melt-freeze temperature cycles, light south/southwest winds 6-9 mph, and a 30% chance of snow Wednesday with a 1 inch accumulation.
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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