Forecaster Observation - Natural avalanches, Nyack Mt., Flathead Range

Location Name: 
Forecaster Observation - Natural avalanches, Nyack Mt., Flathead Range
Region: 
Flathead Range - Middle Fork Corridor
Date and time of avalanche (best estimate if unknown): 
Mon, 03/28/2016 - 20:00
Location Map: 


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path

Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Dry
Slope: 
40degrees
Trigger type: 
Natural
Crown Height: 
2 ft
Aspect: 
Northeast
Weak Layer: 
Unknown
Avalanche Width: 
100ft.
Terrain: 
Above Treeline
Elevation: 
7 000ft.
Bed Surface: 
Unknown
Avalanche Length: 
300ft.
Number of similar avalanches: 
1
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

We observed 2 crowns on a northeast aspect on Nyack Mountain in the Cascadilla drainage while driving home along Highway 2. We suspect they occurred some time yesterday or last night given the northeast aspect. It's probable that the new snow and strong southwest winds yesterday or last night were the trigger. Today's east-northeast winds would likely have redistributed the snow on the top of that slope to the other side of the ridge on Nyack Mountain. Given that the slope is visible from the road, it makes for good observations during clear weather. 

It was difficult to estimate the crown depth of both, but one was slightly deeper than the other. I suspect they were wind slabs. We were unable to obtain photographs due to a lack of opportunity to safely move off the road.

Avalanche 1: SS-N-R1-D2-I. This crown was located on a more uniform slope below the ridge a couple of hundred vertical feet. The crown width was estimated to be about 100-150 feet wide. The crown depth is unknown.

Avalanche 2: SS-N-R1-D1.5-I. This crown was directly beneath the cornice on the ridge in steep, rocky terrain.The crown width was estimated to be about 40 feet wide and the crown depth is unknown, but more shallow than Avalanche 1.

 

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Wind Speed: 
Strong (Whole trees in motion)
Precipitation: 
None
Air temperature trend: 
Wind Direction: 
East
Accumulation rate: 
None
More detailed information about the weather: 

Winds shifted last night (3/28-29) from the southwest to the east.