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Wed, Nov 22, 2017 at 6:56 AM
Issued by: Brian Lazar

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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.
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

One to four inches of new snow combined with strong west and northwest winds created freshly form wind-drifted slabs now stacked on top of older early season snow. The slopes with the best coverage are also the slopes where you're most likely to trigger an avalanche. These are high-elevation slopes that face north and east. You can trigger avalanches from a distance and from below, so give this terrain a wide buffer to address the unpredictability. 

We now have slabs around a foot  thick on east-facing slopes, and you might be able to trigger an avalanche in just the freshly-drifted snow even in areas that don't harbor more deeply buried weak layers. Drum-like or hollow sounds underfoot are signs of this problem. You can reduce your risk by avoiding slopes where you observe active wind loading

The Friends of CAIC are hosting the 10th Annual CAIC Benefit Bash on December 2, 2017 in Breckenridge The funds from this event go to support the CAIC and these backcountry forecasts. It’s an event not to miss. For more information and to purchase tickets visit: https://adecadedeep.eventbrite.com.

 

Recent Tweets

@CAIC: Av season! Poss 2 trigger avs that break nr ground NW-N-SE slopes, esp those w fresh wind drifts. MOD(Level 2) Nov 22, 7:35 AM
@CAIC: Avalanche season up high. B alert 4 cracks whumpfs fresh drifts on/below slopes >35 deg. MOD(L2) N/ATL. Nov 21, 8:40 AM

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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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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N
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NE
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Above Treeline
Near Treeline
Below Treeline
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Very Likely
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Historic
Very Large
Large
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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 Wed, Nov 22, 2017 at 11:51 AM by Brian Lazar Statewide Weather Forecast
  Wednesday Night Thursday Thursday Night
Temperature (ºF) 27 to 32 40 to 45 27 to 32
Wind Speed (mph) 12 to 22 20 to 30 15 to 25
Wind Direction WNW W W
Sky Cover Partly Cloudy Partly Cloudy Partly Cloudy
Snow (in) 0 0 0

Archived Forecasts

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Wed, Nov 22, 2017 at 7:23 AM
Issued by: Brian Lazar Statewide Weather Forecast  

We got just enough snow and wind over the last day or two to complicate avalanche conditions. The 1 to 4 inches of new snow and strong west and northwest winds created fresh wind-drifted slabs around a foot thick. On high-elevation north and east-facing slopes this fresh slab is stacked on top of the the Persistent Slab avalanche problem that formed earlier. This incremental loading will make triggering an avalanche breaking into deeper weak layers a bit easier than a day or two ago. 

We also need to consider south east aspects as well.  On these slopes there are just wind-drifted slabs without the underlying persistent weak layers, but even triggering a Wind Slab avalanche a foot thick could be enough to injure you or bury you in a terrain trap. 

The snow that fell in October and didn't melt off gradually transitioned into weak basal facets and crust-facet combinations. The saving grace is that the early season snow did melt off in most places, so this worrisome snowpack foundation isn't widespread. It is confined to near and above treeline slopes that face northwest to north to east. But, on these slopes you can easily trigger an avalanche. The storm event from last week provided the first test of the weak foundation, and it did not hold up well. Anywhere the new storm snow fell on a preexisting snowpack, we saw evidence of instability: avalanches, shooting cracks, and propagating snowpack tests. 

The saving grace is that the early season snow did melt off in most places, so this worrisome snowpack foundation isn't widespread. It is confined to near and above treeline slopes that face northwest to north to east. But, on these slopes you can easily trigger an avalanche. The storm event from last week provided the first test of the weak foundation, and it did not hold up well. Anywhere the new storm snow fell on a preexisting snowpack, we saw evidence of instability: avalanches, shooting cracks, and propagating snowpack tests. 

The danger is MODERATE (Level 2) because the suspect slopes are not widespread, natural avalanches are unlikely,  and due to lack of snow coverage, very large avalanches are also unlikely. But, the most suspect slopes are also the most attractive for recreating. We're going to be lured to slopes with deeper coverage.  Despite all the rocks, shrubs, and bare ground poking through the thin snow coverage in most places, it is avalanche season up high.

Be cautious near, on, or below, any slope steeper than about 30 degrees that looks like rocks and shrubs are buried and no longer visible. This near miss in the Aspen zone is exactly the type of event we want to avoid. You can trigger avalanches from below or from a distance. Give yourself a wide buffer around potential avalanche terrain to account for this unpredictability.  The Persistent Slab avalanche problem will be with us for a while. 

 


  • Snowpack observations in Sawatch zone 11.18.17
  • Shooting cracks, ENE aspect near Monarch Pass 11.18.17 (full)

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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 Sun Nov 19 Anna Migl No No No

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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Brumley Wed Nov 22 7:00 PM 39 - - - - -
Cottonwood Pass Wed Nov 22 7:00 PM 29 99 6 279 21 -
Monarch Pass (050e200) Wed Nov 22 8:04 PM 33 74 11 5 24 -
Saint Elmo Wed Nov 22 7:00 PM 37 - - - - -
Leadville Wed Nov 22 8:00 PM 35 85 10 330 - -
Porphyry Creek Wed Nov 22 7:00 PM 38 - - - - -

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