• Backcountry Avalanche Forecast
  • Forecast Discussion
  • Observations & Weather Data

Thu, Mar 4, 2021 at 7:05 AM
Issued by: Mike Barney

Thursday

 

Friday

Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential.   Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential.
Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential.   Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential.
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.
  Danger Scale

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Summary

Dangerous avalanche conditions exist.  6 to 8 inches of new snow fell early this morning with strong southwesterly winds. This snow landed on faceted surfaces and can be triggered today where you find eight or more inches of newly drifted snow. An avalanche in the new snow can be large enough to bury a person. It is possible for these avalanches to step down where our avalanche problems over lap, creating a very large unsurvivable avalanche. 

Below treeline slopes will be easy to trigger where the wind has drifted snow below ridgelines or in open areas on northerly and easterly aspects. Lower elevation terrain less steep than 35 degrees can provide safer riding options.  

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Please remember to recreate responsibly, including following state and local public health orders and social distancing recommendations.

 

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


Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

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


Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Weather Forecast for 11,000ft Issued Fri, Mar 5, 2021 at 4:20 AM by Mike Floyd Statewide Weather Forecast
  Thursday Thursday Night Friday
Temperature (ºF) 32 to 37 13 to 18 33 to 38
Wind Speed (mph) 5 to 15 4 to 14 8 to 18
Wind Direction NNE S SW
Sky Cover Clear Mostly Clear Mostly Clear
Snow (in) 0 0 0

Archived Forecasts

  • Select Forecast: Valid

Thu, Mar 4, 2021 at 8:13 AM
Issued by: Chris Bilbrey Statewide Weather Forecast  

A warm, moist storm systems arrived overnight forming fresh Storm Slabs at all elevations. With a mix-bag of old, snow surfaces below the new snow, dense slabs will be reactive to the weight of a rider. Sensitivity may be a bit touchier on northerly-facing slopes where the old snow surface faceted and weakened during the recent warm, dry spell. In addition, firm melt-freeze crust on slopes facing east through south to west may act as a slippery sliding surface and avalanches can travel farther and faster than you might expect.

Since mid-February, the snowpack is less reactive and terrifying avalanche activity has dropped off significantly. The majority of stability test are not popping off the column with excitement ending up in your lap. Despite our Persistent Slab avalanche problem trending down over the last week, looming weak layers have been cranky all season. Storm Slab avalanches triggered from deeper drifts could trigger deeply buried persistent weak layers. This cascade event would result in deeper failures and wider propagating contributing to a more deadly and destructive avalanche. 

Initiating a failure in deeply buried weak layers below a stiff slab takes finding the right combination of depth and structure or the shallow spot on a slope. Stepping out into terrain near 35 degrees at higher elevations is like rolling the dice. Slopes harboring the right combination of depth and structure may tolerate multiple people traveling across or below without avalanching providing a false sense of security. During times like this, it does not matter how much you know about snow, avalanches, or how many years you have spent in the backcountry, recreating on steeper slopes is purely a game of chance.

Weak, fragile facets that formed in December keep rearing their ugly head and surprising observers with lingering sensitivity. A large remotely triggered avalanche outside of Lake City this week is a good reminder that weak snow lurking below can still fail from added weight of a rider or machine. Stubborn slabs may not offer clues of potential danger prior to failure and may even lure you further out onto a slope before breaking above and around you. You can reduce the chance of waking the monsters in the basement by sticking to lower angle slopes without overhead hazards or below treeline slopes.

If uncertainty surrounds your snowpack assessment or you are new to the backcountry, now is not the time to explore bigger, more complex terrain. If you are an old veteran, now is not the time to rely on what you have done in past years. Patience is a strong attribute and know that the snowpack will turn around, but it is not there yet.


  • Large grain facets that lurk at the bottom of the snowpack on an East facing slope just below 10,000 feet. This weak-layer produced propagating failures on Extended Column tests. The Slab on top of this slope was not very stiff, but this kind of setup is important to remember as we prepare for spring storms. The Season is not over! South San Juan March 3, 2021 (full)
  • Snow profile from a near treeline southeast-facing slope with 60 cm of snow above the December facets that make up the bottom 65cm of the snowpack. The December facets are still large and loose and not to far from the surface. This combination is what is making this seasons snowpack more dangerous than recent seasons as we head into March 2,2021 NSJ (full)
  • PIt results. (full)
  • East-facing Yellow Mountain at 12,600'. Unknown timing but possibly recently triggered from strong SW wind Feb 26-27. (full)

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Avalanche Observations
Report Date # Elevation Aspect Type Trigger SizeR SizeD
View Thu Mar 4 - >TL N L N R1 D1.5
View Tue Mar 2 - >TL W WL N R1 D1

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Thu Mar 4 Jeff Davis No Yes (1) No
View Thu Mar 4 Amy Pertuz No No No
View Tue Mar 2 Mike Barney No Yes (1) Yes (1)
View Tue Mar 2 - No No No

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Dynamo Telluride Ski Resort Fri Mar 5 6:00 AM 17 68 23 85 30 -
Kendall Mt Fri Mar 5 5:00 AM 11 91 16 32 31 -
Molas Pass Fri Mar 5 5:00 AM 14 96 2 360 7 2.6
Putney Fri Mar 5 6:00 AM 15 93 15 30 22 -
Swamp Angel Fri Mar 5 6:00 AM 11 89 2 84 5 1.1

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