• Backcountry Avalanche Forecast
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  • Observations & Weather Data

Tue, Feb 19, 2019 at 5:20 AM
Issued by: Chris Bilbrey

Today

 

Tomorrow

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.
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.
  Danger Scale

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Summary

You can trigger avalanches that break in recent storm snow or in older, weak snow. Since Sunday night, low-density snow formed softs slab up to 30 inches thick. Moderate south winds will easily drift snow into stiffer slabs. Expect these to be thicker and more widespread near and above treeline on west to north through east-facing slopes. Look for and avoid rounded pillows and new cornice growth can clue you into heavily wind-drifted areas. Use cracking in the snow surface to help identify areas where a cohesive storm slab exists.

A larger and potentially more dangerous problem is triggering an avalanche in weak, faceted snow that formed during dry weather at the end of January. New snow is not adding a huge load to the snowpack, but modest amounts each day add up and continue to stress weaker snow below. Avalanches triggered in the storm snow can potentially step down to deeper, weak layers. An avalanche that breaks deeper in the snowpack can result in a very large and possibly deadly slide. Avoid travel on and under wind-drifted slopes steeper than 30 degrees at higher elevations or open, wind-prone slopes below treeline. Pay attention to what’s above you and can stick to lower-angled terrain if stability is in question.

 

 

Avalanche Problem

 
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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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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

 
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Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


Loose Dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.

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 7 to 12 -2 to 3
Wind Speed (mph) 7 to 17 10 to 20 11 to 21
Wind Direction WSW SW SSW
Sky Cover Mostly Cloudy Mostly Cloudy Mostly Cloudy
Snow (in) 0 to 2 0 to 1 2 to 4

Archived Forecasts

  • Select Forecast: Valid

Tue, Feb 19, 2019 at 5:46 AM
Issued by: Chris Bilbrey Statewide Weather Forecast  

Heavy snowfall continued across the Southern Mountains Monday delivering abundant cold smoke powder to all mountain locations. 6 to 14 inches accumulated in the North San Juan zone while the South San Juan zone got pummeled with 10 to 24 inches favoring the La Plata Mountains and Wolf Creek Pass. Let’s not forget about the Sangre de Cristo Range who got in on the action with up to 10 inches reported at higher elevations. Storm totals range from one up to three feet of snow since Sunday night.

Our current storm is not adding the same load and shock to the snowpack as the previous storms in February. However, snow water totals range from one to almost two inches of SWE and this is enough of a load to stress buried weak layers that formed during dry weather in late January. As snowfall continues today storm slabs will thicken, become more widespread and may be more reactive than what observations hinted at on Monday (ob 1, ob 2). Small changes in wind direction or breaks in recent storms formed different layers in the upper snowpack. Monitor the impact new snow is having on these interfaces before committing to a slope. Digging into the snow is the best and easiest way to accomplish this and evaluate the ease of triggering an avalanche in recent storm snow.

We are less than a week out from our last natural cycle that produced dangerous avalanches breaking near the ground or on mid-to-upper snowpack layers such as near-surface facets and faceted crust. These avalanches were two to three feet deep, large, and dangerous. CAIC forecasters traveled near Ophir on Sunday and observed clean and fast shears at the interface between the old snowpack and bottom of February snow. Anticipate that an avalanche triggered near the surface could step down to deeper weak layers making a larger and potentially more deadly avalanche.

We also can’t ignore facets and depth hoar near the ground. On a lot of slopes throughout the San Juan’s, these scary layers are now buried under a two meter thick slab.  Many slopes that avalanched in mid-January harbor weak facets sitting above a firm old bed surface below a cohesive slab. These areas are primed and ready to avalanche if they didn’t during last week’s cycle. Some of these slopes might only be waiting for a trigger to fail. Larger storm slab avalanches or avalanches failing on faceted snow below February snow could step all the way down to the ground and create an un-survivable avalanche.

The general trend of the snowpack is good on a seasonal scale as we are building a deeper and stronger snowpack. For today, dangerous conditions exist and the snowpack needs time to adjust to the new load and find equilibrium from abundant snowfall this month. Continue to be diligent in your snowpack evaluations and consider the consequences of triggering a larger avalanche before committing to steeper terrain.

 


  • CAIC forecasters traveled in the La Plata Mountains to evaluate and test the snowpack structure on slopes that slid during the mid-January cycle. They found a three-foot-thick slab above weaker snow sitting on top of the old bed surface. Extended Column Test produced propgating results with moderate force. Slopes with this similar structure could avalanche again with the additional load.
  • CAIC forecasters traveled in the alpine to evaluate sensitivity in persistent weak layers on northwest aspects and extent of recent wind-drifting from strong southwest winds. They found stiff, stubborn slabs sitting above a soft collapsible layer formed during recent dry weather and large facets and depth hoar persisting above the ground.

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Avalanche Observations
No relevant backcountry observations found for this forecast

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Mon Feb 18 Chris Bilbrey No No Yes (2)
View Sat Feb 16 Mark Mueller No No No

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow

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