• Backcountry Avalanche Forecast
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Fri, Jan 17, 2020 at 7:23 AM
Issued by: Chris Bilbrey

Today

 

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.
Low (1) Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.   Low (1) Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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Summary

Strong south to southwest winds and up to 4 inches of new snow means you could trigger avalanches today on wind-drifted slopes. Thicker surface slabs are found on slopes facing north to east through southeast with deepest drifting below ridgelines and on steep sidewalls of gully features in the alpine. Pay attention as you climb higher in elevation and into the transition zone between near and above treeline terrain. There, you may find isolated areas with similar drifting as alpine slopes. Use caution on any slope where you find more than about 8 inches of new or drifted snow.  

Triggering a shallow slide in the upper snowpack could break deeper in older, weak snow. Fragile, buried weak layers continue to be the most reactive on east to south-facing slopes. Watch for cracking in the snow surface and heed the warning sign of audible collapses. Both suggest that a weak and collapsible layer most likely lurks underneath your feet. Pay attention to the direction the slope faces, manage your terrain selection to avoid drifted slopes steeper than about 35 degrees, and seek safer riding options in wind-sheltered terrain.

 

Avalanche Problem

 
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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.

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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N
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E
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Above Treeline
Near Treeline
Below Treeline
Certain
Very Likely
Likely
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Avalanche Character Aspect/Elevation Likelihood Size

What You Need to Know About These Avalanches


Wet Slab avalanches occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoid avalanche terrain when you see pinwheels, roller balls, loose wet avalanches, or during rain-on-snow events.

Weather Forecast for 11,000ft Issued Fri, Jan 17, 2020 at 12:40 PM by Jason Konigsberg Statewide Weather Forecast
  Friday Night Saturday Saturday Night
Temperature (ºF) 0 to 5 24 to 29 10 to 15
Wind Speed (mph) 10 to 20 7 to 17 6 to 16
Wind Direction WSW SW WNW
Sky Cover Mostly Clear Partly Cloudy Partly Cloudy
Snow (in) 0 0 0

Archived Forecasts

  • Select Forecast: Valid

Fri, Jan 17, 2020 at 8:09 AM
Issued by: Chris Bilbrey Statewide Weather Forecast  

Phase one of a two-phase storm system passed to our south and east overnight. Light snowfall and strong south to southwest winds built fresh, shallow surfaces slabs throughout the Southern Mountains. Generally, one to two inches of new snow is reported with up to four inches on Wolf Creek Pass. An additional three to five inches of snow is possible today before the storm quickly exists to the east. The next round of precipitation comes with a bump in wind speeds from a cold front this afternoon contributing to more blowing and drifting snow.

This new, light load should not overload and tip the scale on the generally strong snowpack in the San Juan Mountains. Smaller snowfall totals in the Sangre de Cristo range means no change to the avalanche danger for today, but an overall shallower, weak snowpack structure exists there. With each strong wind-loading event during January in the San Juan Mountains, we’ve seen natural avalanches popping in the alpine – be on the lookout for similar conditions today and tomorrow.

The most obvious and easier to manage avalanche problem today is newly formed wind-drifted slabs on leeward slopes. Thickest and potentially more reactive drifts are found in areas that received the most snowfall – the South San Juan zone favoring the eastern side. These fresh slabs formed above a variety of old snow surfaces such as wind-stiffened alpine surfaces, thin melt-freeze crust on sunny slopes, and decomposing fragments/ near-surface facets on shady slopes. New snow densities around 10% may promote good bonding with firm surfaces but the new snow may be easier to trigger where softer snow is found below. Denser snow increases slab strength and this may allow it to rest above weaker snow waiting for an extra push from a rider or machine before avalanching. On the flip side, a more cohesive slab has potential to break wide than expected, run farther, and entrain more snow leading to a larger, more violent avalanche.

Continue to use caution on slopes facing east, southeast, and south at higher elevations. Since January 1st, the largest proportion of natural avalanches have occurred on those aspects (49 out of 72) in the North and South San Juan zones. Although rider-triggering on those same aspects has been limited, a rider in the North San Juan zone on Tuesday triggered a large avalanche near treeline on a southeast-facing slope. This avalanche is bulls-eye information that our Persistent Slab avalanche problem may be coming back into play near treeline in more areas. A series of buried crust/ facet combinations as well as lingering depth hoar remain along with an overall shallower snowpack. Slopes with overlapping Wind Slab and Persistent Slab avalanche problems have potential for a shallow slide to step down into deeper weak layers producing a more dangerous slide that would be difficult to survive.

Northwest aspects still remain the most concerning of north-facing terrain due to more scouring and loading. This has contributed to highly variable snow depth and overall snow cover. Shallower areas with weak, faceted, cohesionless snow may have stiffer snow above making for a complex pattern. Managing your terrain selection is key to avoiding an avalanche encounter today and strive to avoid likely trigger locations such as the edge of the slab or near rocky outcrops.


  • Looking downslope of a natural avalanche that failed in a thick wind-drift area below the ridgeline. Parrot Peak, La Plata Mountains. South San Juan. January 13, 2019. (full)
  • Strong winds have scoured west and southwest aspects in the alpine. Deeper snow depths exists in leeward terrain. Lewis Mountain, South San Juan zone. January 13, 2019. (full)
  • Slab avalanche on a Southeast facing cross-loaded slope near Turk mountain above Molas Pass. January 13th, 2020. (full)
  • This hard slab easily broke apart with the first shovel swipe at the snow. Weak, near-surface facets sit below the pencil hard slab. These hard, drummy slabs are found on all open slopes in the alpine. Upper Coal Creek, South San Juan zone. January 9, 2019. (full)
  • Snowpit on a southeast aspect above treeline. Upper Coal Creek, South San Juan. January 9, 2019. (full)

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Avalanche Observations
Report Date # Elevation Aspect Type Trigger SizeR SizeD
View Fri Jan 17 - TL NE SS AS / c R2 D1.5

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Field Reports
Report Date Observer Snowpack Obs Avalanches Media
View Fri Jan 17 Mark Mueller No Yes (1) No

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Wolf Creek Pass Sat Jan 18 3:00 AM 5 86 13 201 17 4.0
Columbus Basin Sat Jan 18 1:00 AM 14 - - - - 7.0
Lily Pond Sat Jan 18 2:00 AM 10 - - - - 2.0
Spud Mountain Sat Jan 18 1:00 AM 7 - - - - -
Upper San Juan Sat Jan 18 1:00 AM -3 - - - - 5.0
Wolf Creek Summit Sat Jan 18 1:00 AM 9 - - - - 5.0

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