Avalanche near Keeler Warming Hut. January 24th

Location Name: 
Above Keeler-Rattle warming hut
Region: 
Kootenai Area
Date and time of avalanche (best estimate if unknown): 
Thu, 01/24/2019 - 10:30
Location Map: 
United States
48° 19' 2.1792" N, 116° 4' 25.7016" W
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain

Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Slab
Slope: 
40degrees
Trigger type: 
Snowmobiler
Crown Height: 
2 ft
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Avalanche Width: 
100ft.
Terrain: 
Near Treeline
Bed Surface: 
Old Snow
Avalanche Length: 
100ft.
More detailed information about the avalanche: 

Received a report from a snowbiker on January 29th of an avalanche incident that occurred on January 24th on a steep slope above the Keeler warming hut often referred to as the "corner bowl". The reporting party indicated that the slide took place when he stopped above a steep roll. The avalanche broke below him and encompassed and area 100' wide by 100' long. It released on the buried surface hoar layer approximately 18" deep. No one was caught or buried in the incident and the triggering rider remained at the top of the crown area. Field observations yesterday revealed that this layer is becoming stubborn and difficult to trigger but still has the potential to release in isolated areas, particularly protected gullies and mountain drainage bottoms. Big thanks to the reporting party and please keep the observations coming!

Snowpit or crown profile photo or graph: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

Weather conditions leading up to this event consisted of a period of high pressure and valley inversion that caused a widespread layer of surface hoar to develop across the area below 6,500'. This weak layer was successively buried by two seperate storm layers that developed into a cohesive slab layer. Stability test were performed in this area the day of the incident and revealed that this layer was failing and propating with moderate force (ECTP19). An avalanche warning was issued for High Danger the day prior to this incident due to the combination of surface hoar, crust and a recent storm loading event. Multiple days of mild temperatures in the mountains are making this layer difficult to trigger right now but it is still widely found across the area and has the potential to continue being a problem throughout the week.