Forecaster Observation - Skyland area, Flathead Range

Location Name: 
Forecaster Observation - Skyland area, Flathead Range
Region: 
Flathead Range - Marias Pass/Skyland
Date and time of observation: 
Tue, 03/29/2016 - 12:00
Location Map: 

Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

The objective today was to assess new storm snow and wind slab development in an area closest to the Continental Divide within the advisory area. The storm deposited substantial snow (20 inches recorded at Flattop SNOTEL in GNP) in the northern half of GNP which is outside of the advisory area. At the Skyland area we measured about 4 inches of new snow in the past 24 hours and another 4-6 inches from the day before for a total of about 8-10 inches above the melt-freeze crust from last weekend (3/26). We observed substantial wind loading from strong east winds, but our location was rather sheltered from these winds. Plumes of drifting snow were visible on the ridges of the highest peaks, but only at those upper elevations (not at middle and low elevations). Thus, wind slabs appeared to be forming off ridges on northwest, west, southwest, and south aspects. 

We assessed snowpack conditions on a southeast aspect to determine how the surface snow was developing with above freezing temperatures and a fair amount of sunshine today. 

  • Aspect: 110 degrees (southeast)
  • Slope angle: 32 degrees
  • Total snow depth (HS) = 265 cm

We investigate the top 160 cm of the snowpack.

  • ECTN 15 at 20 cm from the surface
  • ECTN 27 @ 40 cm from the surface
  • The suspected late Feb. melt-freeze crust is located 110 cm from the surface in this pit. A layer of 4F weak, sugary snow exists below this crust, but this layer did not fracture or propagation in our stability tests.
  • No layer in our snowpit propagated fracture in Extended Column Tests.

We observed 2 crowns on a northeast aspect on Nyack Mountain in the Cascadilla drainage while driving home along Highway 2 that likely occurred yesterday (3/29). See description below or here.

We observed 2 glide cracks on southeast aspects in the general area.

Snowpack photos: 
Any other comments about the observation or links to outside pages that have more info on the observation: 

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: 
Above Freezing
Wind Speed: 
Moderate (Small trees sway)
Precipitation: 
None
Wind Direction: 
East
Accumulation rate: 
None
More detailed information about the weather: 

Winds shifted overnight from the southwest to the east. Winds were mostly prevalent in exposed, upper elevation areas. In sheltered areas on sunny slopes, it felt rather warm and spring like.

Activity: 
Snowmobiling