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Tue, Feb 19, 2019 at 6:29 AM
Issued by: Mike Cooperstein

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Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.   Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.
Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.   Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.
Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.   Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully.
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Summary

You can trigger avalanches that break just below the most recent storm snow or avalanches that break deeper on mid-pack weak layers. If you trigger an avalanche just below the recent storm and wind-drifted snow it can break 1 to 3 feet deep. If you trigger an avalanche on a mid-pack weak layer it can break much deeper and be much more dangerous. The mid-pack weak layers are more reactive on east and southerly-facing slopes where they are found around a crust. Look for these weak layers before riding in steeper terrain. You are most likely to trigger larger more dangerous avalanches on previously wind-loaded slopes at higher elevations or just below ridgelines. Avoid slopes where you see evidence of previous wind-loading such as cornices along ridgelines and smooth sculpted snow surfaces. You can always reduce your chance of being caught in a dangerous avalanche by sticking to lower angle, westerly-facing, or wind sheltered terrain.

 

Avalanche Problem

 
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N
S
E
W
NW
NE
SE
SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
Large
Small
Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


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.

Avalanche Problem

 
problem icon
N
S
E
W
NW
NE
SE
SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
Large
Small
Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


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.

Avalanche Problem

 
problem icon
N
S
E
W
NW
NE
SE
SW
Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
Possible
Unlikely
Historic
Very Large
Large
Small
Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


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.

Weather Forecast for 11,000ft Issued Tue, Feb 19, 2019 at 12:04 PM by Mike Cooperstein Statewide Weather Forecast
  Tuesday Night Wednesday Wednesday Night
Temperature (ºF) -9 to -4 3 to 8 -3 to 2
Wind Speed (mph) 8 to 18 13 to 23 6 to 16
Wind Direction W WSW SSW
Sky Cover Mostly Cloudy Mostly Cloudy Mostly Cloudy
Snow (in) 0 to 2 0 to 2 0 to 1

Archived Forecasts

  • Select Forecast: Valid

Tue, Feb 19, 2019 at 7:55 AM
Issued by: Mike Cooperstein Statewide Weather Forecast  

You can trigger avalanches on a layer of weak crystals just below the most recent storm snow. These avalanches can break over a foot deep and can break in surprising ways. The most dangerous layer is a layer of near-surface faceted crystals buried in the middle of the snowpack 1 to 3 feet deep. Snowpack tests and explosives results have shown that this layer is easier to trigger on easterly and southerly-facing areas where it is buried around a crust. If you trigger an avalanche that breaks a couple feet deep you might be able to escape, but in wind-loaded areas below ridgelines or in open wind prone bowls this weak layer could be buried much deeper and could result in a large possibly inescapable slide. We have also seen avalanches start on this layer and step down to the ground resulting in large dangerous avalanches. Since we have not had a lot of reports of cracking and collapsing around this layer, you will have to dig down and assess for the presence and the stability of this layer before riding. 

Weak layers in the upper snowpack are easier to trigger because they are closure to the surface and they can last for weeks or even a month. Look for mid-pack weak layers and assess their strength before riding in steep terrain.

 


  • Small skier triggered Storm Slab avalanche on Buffalo Pass (full)
  • Small skier triggered Storm Slab avalanche on Buffalo Pass (full)

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Avalanche Observations
Report Date # Elevation Aspect Type Trigger SizeR SizeD
View Mon Feb 18 - <TL NE SS N R2 D2

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Mon Feb 18 Dan Edmiston No Yes (1) No
View Mon Feb 18 Ben Tiffany No No No
View Sat Feb 16 Nicholas Sedney No No Yes (1)

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Storm Peak Observatory Tue Feb 19 8:50 PM -8 89 8 144 9 1.0

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