• Backcountry Avalanche Forecast
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Sat, Nov 17, 2018 at 7:27 AM
Issued by: Ethan Greene

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

You can trigger an avalanche large enough to injure or bury you in steep wind-loaded terrain. The avalanche danger is highest on wind-loaded slopes that face north through east and are near or above treeline. These slopes are relatively easy to identify in the field. Look for and avoid smooth, wind-sculpted features. These old wind drifts form pillows or areas where deeper snow lies below ridgelines. You will find them along the sides of subridges and gully walls. A ride in even a small avalanche today could have serious consequences if it drags you through the rocks, over a cliff or into trees.

The avalanche danger is slowing decreasing as the time since our last significant snowfall increases. This means it is getting harder to find a place to trigger an avalanche. It also means that when you find the right spot the avalanche you trigger will break into harder, denser snow. You are most likely to trigger an avalanche in an area of shallow snow as you are moving onto or off of an old wind drift.

In these more wind-sheltered areas, the snow surface has faceted and lost cohesion. You could trigger small loose avalanches or sluffs on very steep slopes. They are entraining enough snow to push you around or take you for a ride. If the snow surface feels weak and unconsolidated, consider where the sluffing snow might carry you.

 

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


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.

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.

Weather Forecast for 11,000ft Issued Sat, Nov 17, 2018 at 4:20 AM by Brian Lazar Statewide Weather Forecast
  Saturday Saturday Night Sunday
Temperature (ºF) 25 to 30 10 to 15 25 to 30
Wind Speed (mph) 5 to 15 0 to 10 2 to 12
Wind Direction WSW WNW NW
Sky Cover Mostly Cloudy Mostly Cloudy Mostly Clear
Snow (in) 0 to 1 0 to 1 0

Archived Forecasts

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Sat, Nov 17, 2018 at 8:30 AM
Issued by: Ethan Greene Statewide Weather Forecast  

In the Central Mountains, you can still trigger a large avalanche on wind-loaded terrain features. Reports of avalanches have slowed to a trickle. Most of the avalanches in the last week released on above-treeline slopes that face northeast and east. There was one avalanche that released on a near treeline slope and one that released on a northwest aspect. This decrease in avalanche activity with no significant weather events is a sign that the avalanche danger is decreasing. 

The source of avalanche danger remains the chance of triggering a Persistent Slab avalanche. The primary weak layer is old faceted snow that arrived in October. Snow and wind events in November built slabs and the combination is our problem today. The key to staying out of trouble is to identify and avoid these old drifts.

The avalanche danger is decreasing as the Likelihood of triggering one of these features decreases. With time it gets harder to trigger one of these avalanches and the number of places you can release one also drops. This is a slow process. It creates a patchwork of dangerous areas where you can travel over slopes with the troublesome characteristics without incident and then find a place to trigger a slide. 

There is a stark gradient in snow depth as you move up in elevation. Below about 10,500 feet the snowpack is fairy thin or nonexistent. The snow depth increases fairly quickly above about 11,00 feet. The avalanche danger follows this pattern. In areas at a higher elevation and in the northern portions of the Aspen and Sawatch zones, you will find deeper snow cover and a greater chance of triggering a dangerous avalanche. Here the slabs are thicker and more widely distributed.

The recent spate of dry weather is changing the snowpack.  The faceting process is weakening the snowpack overall. In shadier terrain, the surface is becoming cohesionless.  If you find layers of weak granular snow that are at least a few inches thick at the snow surface. You can start a Loose Dry avalanche in very steep terrain.  Consider the terrain below you.  The sluff you or someone above you triggers might grow large enough to knock you off your feet.

 


  • Northeast and east-facing slopes near Marble. The red circles indicate isolated wind-drifted areas where you might be able to trigger a slab avalanche breaking on a buried crusts about 30cm deep. 11.12.18 (full)
  • Small Loose Dry avalanches about 30cm deep. East aspects off Marble Peak. 11.12.18 (full)

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Avalanche Observations
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Field Reports
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Weather Observations
Station Date Time Temperature Relative Humidity Wind Speed Wind Direction Max Gust 24 Hr Snow
Butte Sat Nov 17 10:00 AM 35 - - - - 1.0
Park Cone Sat Nov 17 11:00 AM 28 - - - - 1.0
Taylor Park Sat Nov 17 10:57 AM 41 28 3 75 6 -

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