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Professional Observation

Basic Information

Observation Details

Observation Date:
February 4, 2020
Submitted:
February 4, 2020
Observer:
SAC - Davis
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Boulders - Silver Pk to 9,900'

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced
Cracking in fresh drifts up to 20 cm deep. I walked and rode through several wind-loaded pockets and couldn't get these cracks to propagate more than 5' in front of me.

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Bottom Line

I observed ample signs of strong to extreme wind along the Boulder Foothills (see photos). I encountered thin fresh wind press and micro wind slabs at middle and upper elevation. These slabs cracked and slid in chunks in front of my board but never broke much wider than that. These small slabs were the most sensitive in areas where they sat atop loose facets or slick icy layers near the surface.

I would have avoided areas where this wind-loading was a bit more effective at building a thicker slab. Due to the strong wind, this appears to have occurred in areas that are generally more sheltered (that saw wind-loading but weren't obliterated) or lower down off the ridge lines in more protected bowls and cirques.

Media

Drainage wind yesterday and last night cross-loaded these mid-slope gullies in the Boulder Mountains.
Baker Creek Parking Lot - Extreme wind raked these trees stretching dirt and debris the length of several football fields.
Baker Creek Parking Lot - Extreme wind snapped our poor beacon park sign clean in half.

Advanced Information

Weather Summary

Cloud Cover:
Clear
Temperature:
Teens (est.)
Wind:
Light , NW

Clear and cold. I observed some blowing snow along the ridge between Lorenzos and Silver early in the day but it was short-lived. Wind was intermittent and light at 9,900'.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1 Past 24 hours Boulder Peak
E 		D2 Couldn't get a look at the starting zone but the debris was pushing D2. None

Took a look at the previously reported slide in Eagle Creek from afar. My photos ended up blurry but the crown obviously stepped down to a deeper weak layer.

Snowpack Observations

9000', W, 33 deg:
Snow depths at middle elevations were around 100 cm. Thin 5-10 cm wind skin (1F) sat on the surface in most locations including in the trees. This wind skin was not bonding well to a 20 cm thick layer of weak facets (F) underneath. The mid-pack was a stiff (1F) slab and the lower pack consisted of 2-3 mm facets. The hardness of the lower pack ran from 4F to 4F+ (moist) at the base.

Upper elevation slopes were highly variable ranging from deep, rock-hard, icy drifts to trapdoor shallow snow (50 cm) comprised entirely of facets.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 20-60 cm
Slabs were thin in the terrain I traveled. Depth is estimated from observations of cross-loaded features and nearby recent slides. Exposed areas were stripped of new snow. Loading occurred in interesting patterns and low on slopes.
Persistent Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 50-100 cm
Weak snow in a variety of configurations near the ground. Distribution based on previous pro obs.

Terrain Use

I traveled through mid-30 degree terrain that lacked a fresh wind slab at the surface.

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