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Tue, Dec 10, 2019 at 7:46 AM
Issued by: Mike Cooperstein

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Tomorrow

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 large enough to bury you. Since there is more snow in the starting zones, avalanches will be larger making any ride hard to survive. The most dangerous slopes are near and above treeline; however, the upper portions of the below treeline elevation band also has weak snow near the ground with a thick slab on top. Use care if you are traveling in steep areas in the transition zone between the near and below treeline elevation bands.

Avoid steep slopes that face northwest through northeast to east and any slope where you find recent deposits of new wind drifted snow. If the winds increase today from the northwest, watch for fresh drifts on southeast-facing slopes. Careful route-finding is important. You can find safer and enjoyable riding options in wind sheltered low angle terrain.

 

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.

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


Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Weather Forecast for 11,000ft Issued Tue, Dec 10, 2019 at 12:45 PM by Jason Konigsberg Statewide Weather Forecast
  Tuesday Night Wednesday Wednesday Night
Temperature (ºF) 7 to 12 25 to 30 5 to 10
Wind Speed (mph) 6 to 16 5 to 15 5 to 15
Wind Direction WSW WSW NW
Sky Cover Partly Cloudy Increasing Mostly Cloudy
Snow (in) 0 0 0 to 1

Archived Forecasts

  • Select Forecast: Valid

Tue, Dec 10, 2019 at 8:05 AM
Issued by: Chris Bilbrey Statewide Weather Forecast  

Do you remember where you were on November 19? That date is less than three weeks ago and then, we were talking about thin and discontinuous snow cover and barely enough snow to slide on. Turn the page to December 10 and the mountains look a whole lot different and have a much more dynamic snowpack.

There are two snowpack concerns to look out for. The first lies near the surface and the second is at the bottom. Several observations throughout the San Juan Mountains highlight one if not two surface hoar events that are now buried under a cohesive slab. This persistent weak layer will lay silent below a slab until a rider, machine, or a new load collapse these delicate feathers and the snow above comes crashing down. Observations highlight reactive surface hoar near Wolf Creek Pass and in the Telluride area but digging into the snow is the only way to determine its presence. Northerly, wind-sheltered terrain is where this weak layer stayed preserved.

The larger and more dangerous avalanche issue is the October snow that survived at the bottom of the snowpack. This snow metamorphosized into facets and depth hoar and has been reactive with each loading event. It’s now buried under a three to four-foot-thick slab. The stiffness of the overlying slab makes it more difficult for a rider or machine to impact this weak cohesionless layer and trigger an avalanche. If you do find the not so sweet spot, it may propagate wider across the slope than expected and lead to an avalanche that would be difficult to survive. Most likely trigger locations are near the edge of the slab or near rock outcrops where the snowpack in shallow.

Winds shifted from the southwest to northwest overnight. This may increase the distribution of wind-drifted slabs in the alpine. These should be generally small and easy to avoid. You might encounter new drifts on southeast and south-facing slopes forming above a firm melt-freeze crust. These drifts may not bond well to the old snow surface and could move quickly down slope with ski pressure. 

The bottom line is that our snowpack has some complexity to it. Different weak layers and variable snow depths make for tricky conditions. In the deepest areas the snowpack is showing some signs of promise and strengthening. If it continues to snow, we may eventually have less concerns with basal weak layers. However, it’s still too early to determine and caution is advised. Without a careful snowpack evaluation, paying attention to general snow depth, weak layer type and reactivity, you should consider simply avoiding steep slopes that face a northerly or east aspect.

 


  • SE aspect near Mt. Wilson South at 13,000'. SS failed at old snow interface. December 8, 2019. (full)
  • Lingering basal facets. East aspect at treeline. NSJ 12/9/18 (full)
  • Snowpit on an east aspect at 11,900'. ECTP22 x 2. NSJ 12/9/18 (full)
  • 2019-12-07 in Northern San Juan (full)

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Avalanche Observations
Report Date # Elevation Aspect Type Trigger SizeR SizeD
View Tue Dec 10 - >TL NE SS N R3 D2
View Tue Dec 10 - >TL N SS N R2 D2
View Mon Dec 9 - >TL SE SS N R1 D2
View Mon Dec 9 - >TL NW SS N R1 D2

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Tue Dec 10 Jeff Davis No Yes (1) Yes (8)
View Tue Dec 10 Bill Nalli Sandy East No No Yes (5)
View Tue Dec 10 Jonathan Cooper No No No
View Tue Dec 10 Ann Mellick No Yes (1) Yes (4)
View Tue Dec 10 Michael Ackerman No No Yes (2)
View Tue Dec 10 Jasper Thompson No No No
View Mon Dec 9 Ann Mellick Jeff Davis No No Yes (6)
View Mon Dec 9 Jason Bushey No No No
View Mon Dec 9 Bill Nalli No Yes (2) Yes (2)
View Mon Dec 9 Jasper Thompson No No No

See All Field Reports

Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Beartown Wed Dec 11 1:00 AM 18 - - - - 2.0
Dynamo Telluride Ski Resort Wed Dec 11 2:00 AM 21 26 7 244 13 -
Putney Wed Dec 11 2:00 AM 18 26 1 158 5 -
Swamp Angel Wed Dec 11 2:00 AM 11 68 3 100 6 -
El Diente Peak Wed Dec 11 1:00 AM 12 - 2 220 - -
Lizard Head Pass Wed Dec 11 1:00 AM 9 - - - - -
Lone Cone Wed Dec 11 1:00 AM 15 - - - - -
Molas Lake Wed Dec 11 1:00 AM 10 - - - - -
Slumgullion Wed Dec 11 1:00 AM 24 - - - - -

See All Weather Observations