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Tue, December 9th, 2014 - 7:00AM
Wed, December 10th, 2014 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

A  CONSIDERABLE  avalanche danger exists this morning on all aspects above 1500ft. Below 1500ft a lack of snow cover results in No Rating. Over the past 48-hours, heavy rainfall at the mid-elevations and below has created widespread natural wet avalanche activity. With a decrease in precipitation expected today, natural avalanche activity is expected to decline. However, human triggered wet avalanches, up to a foot deep, will remain likely on slopes steeper than 35 degrees. Areas of most concern are all aspects in the elevation band from 1500ft to 3000ft. At the high elevations above 3000ft, storm snow instabilities exist in the form of wind slabs, cornices and loose snow sluffs.

For today, avoiding slopes steeper than 35 degrees harboring  saturated and wet snow is recommended. In the upper elevations with dry or moist snow, cautious route finding and skilled snowpack evaluation is essential.


The next advisory will be Thursday Dec11th at 7am.

Avalanche Outlook for Wednesday: The avalanche danger is expected to decrease Wednesday due to a decrease in precipitation and a possible break in cloud cover. Temperatures should remain very warm however and extra caution will continue to be warranted for wet avalanches below 3000ft and wind slab avalanches above 3000ft.

Special Announcements

Our thoughts and condolences go out to the family and friends of Erik Peterson  who was tragically killed Saturday, Dec 6th while skiing in the Alaska Range. Preliminarily information can be found  HERE.

Upcoming  FREE  Avalanche Awareness talks from CNFAIC forecasters:

Tonight, Dec 9th at 6pm – REI Anchorage.   A few spots are left.   Visit the  REI website  to sign up.

Thursday Dec 11th at 6:30pm – Alaska Avalanche School in Anchorage.    Installment #2 of our Fireside Chat Series.   This evening’s topic will be “Avalanche Basics and Rescue Fundamentals”.

Tue, December 9th, 2014
Above 2,500'
3 - Considerable
Avalanche risk
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Dangerous avalanche conditions. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Yesterday marked the second, and most intense, period of rain on snow. Many wet loose avalanches were observed on all aspects along with two wet slab avalanches between 1500ft to 3000ft (photos below). Today precipitation is expected to decrease with potentially .3-.5″ of rain falling below 2500ft.

Wet avalanches are common during extended periods of rain and warm temperatures. They typically start on steep terrain with rollerballs initiating under cornices, trees, rocks or underfoot that subsequently entrain more and more snow as they gain momentum and move downslope. If caught in a wet avalanche it is very difficult to escape as the heavy wet snow can quickly knock you off your feet, twist a knee or break a leg. Debris has the potential to run further than expected due to a melt/freeze crust 8-18″ below the surface (mid-pack) providing a uniform sliding surface.

Photo below is a wet slab avalanche on the West face of Lipps Ridge (2800ft).


Wet loose avalanches off of Tincan’s Southwest facing CFR ridge (2500ft)

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Despite the grim facts concerning the wet snow stated above, at the high elevations it is snowing. Above 3,500′ new snow amounts during the past 48-hours are estimated between 2 and 3+ feet in the Turnagain Pass zone – up to twice that in other areas such as Portage and the Girdwood Valley. We have little information on how this new snow is adjusting, however what we do know is this is a significant load in a short period of time that warrants respect.

Storm snow instabilities will be in form of wind slab, cornices and loose snow sluffs. With ridgetop winds and precipitation decreasing overnight, these instabilities should gain strength rather quickly. This is due to the warm temperatures of the new snow along with no known preexisting weak layers in the snowpack at these upper most elevations. 


Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Although we did not see any glide avalanche activity yesterday, the poor visibility and known existence of glide cracks between 1,500 and 3,500′, is enough evidence that these types of avalanches remain a concern. As with the travel advice for wet avalanches above, today is a day to avoid slopes steeper than 35 degrees and to steer clear of runout zones.

Tue, December 9th, 2014

Yesterday’s weather was warm, wet and windy. During the past 48-hours Turnagain Pass has received 2.5 inches of water with greater amounts in the Girdwood and Portage Valleys. The rain/snow line hovered ~2000 feet yesterday and possibly up to 2500 feet in areas. Ridgetop temperatures have been ~30F and winds were predominantly from the East, averaging 30-40mph with gusts in the 60’s.  

Overnight, temperatures have increased slightly and the rain/snow line looks to be just above 2000 feet with precipitation diminishing. Winds have also decreased and are remaining steady in the teens to 20’s mph along ridgetops from the East.  Today, Tuesday, we are expecting .3-.5″ of rain below 2000-2500′ with 2-4″ of wet snow above. Ridgetop Easterly winds should remain in the 10-20mph range with temperatures near 30F.

The low-pressure system that moved through yesterday is headed inland today bringing a slight break in precipitation. However, warm temperatures are expected to continue over the next few days with periods of light rain and freezing rain. This should continue through Thursday, followed by another low-pressure system that could bring more precipitation closer to the weekend for Southcentral Alaska.  

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36   0   1.4   19  
Summit Lake (1400′) 35   0   0.2   4  
Alyeska Mid (1700′) 37   0   1.3   12  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   E   25   61  
Seattle Ridge (2400′) 31   E   18 47  
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.