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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, December 12th, 2016 - 7:00AM
Expires
Tue, December 13th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

A generally  LOW  avalanche danger exists across all elevations bands for the Turnagain Pass zone. Triggering a 1-2′ avalanche is unlikely but not impossible. The most suspect slopes are in steep terrain at the high elevations where someone just might be able to break off an old wind slab or find a slope with the buried surface hoar that hasn’t slid. Good travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones are key ways to minimize risk.  Ease onto steep slopes and be prepared to change your plans if an area becomes too crowded.

There is snow to sea level, just enough to put a  LOW  danger rating on the Below Treeline Elevation band. If venturing into the ‘periphery’ forecast zones, such as Girdwood Valley, more caution is advised due to limited information about the snowpack in these areas.  This should also be part of the equation if you are heading to ice climb in  Portage where even  a small slide could have high consequences.

If headed to Summit Lake check out the Saturday Summit Lake Summary  HERE.  

Special Announcements

Mark your calendar for this week’s  Fireside Chat: Avalanche Awareness and Rescue  w/CNFAIC in Girdwood at the  Powder Hound Ski Shop! December 15 @ 6:30 pm – 8:00 pm. FREE.  

The Friends of the CNFAIC is offering two $500 avalanche education scholarships through the Rob Hammel fund. One is for avalanche professionals and the other is open to anyone!  The deadline for both scholarships is Dec 15th! For more information click this link  HERE.  

Thanks to everyone who took time out of their beautiful sunny weekend to collect observations and submit them! We really appreciate the information!

Mon, December 12th, 2016
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

Over the weekend many people were out in the mountains slope testing and there were no human triggered avalanches reported. With a stable weather pattern dominating our region and very little changes affecting the snowpack we are in a Normal Caution phase for avalanche issues. These include:

1- Triggering an outlier avalanche. This would most likely be an ‘unsupported slab’ that sits above a cliff or steep rocky terrain. More on this below in ‘Additional Concerns.’

2- Triggering an old wind slab – Avoid hard stiff snow sitting in steep rocky terrain where a small isolated wind slab could have high consequences.  

3- Triggering a cornice fall. Cornices are small right now, but similar to wind slabs they could take you down somewhere you don’t want to go. Give cornices a wide berth.

4- Sluffs on steep slopes. Small sluffs were observed yesterday, and as the surface snow becomes weaker under clear skies the potential for bigger stuff will increase. 

Remember LOW hazard doesn’t mean NO hazard! Look for signs of instability and use good travel techniques.

Final ridge up Pastoral, near 4400′ Photo: Andy Moderow

Additional Concern
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

Even with LOW avalanche danger it is still important to remember the weak layer 1-2′ below the surface i.e. the notorious Nov 16th buried surface hoar. Although we have not seen an avalanche release in this layer since December 3rd and the slab character has been changing due to the cold temperatures, there are still slopes away from the ‘popular’ zones that have yet to be tested. These are the areas most suspect. Triggering is unlikely but not impossible! 

 

Weather
Mon, December 12th, 2016

Yesterday was cold, clear and calm. An inversion kept ridge top temps in the teens to low 20Fs and lower elevations in the single digits or below zero. This was true overnight as well.  

Today and tomorrow will be similar with clear skies, light N-NW winds and temperatures ranging from single digits in the valleys to  teens and low 20Fs at higher elevations.

According to the NWS “the rather stagnant weather pattern will be  changing dramatically” later in the week. Precipitation and warmer temperatures are forecasted. Stay tuned!  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 14   0    0 20  
Summit Lake (1400′)  3 0  0 4  
Alyeska Mid (1700′)  17 0    0  9

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  20  W  5  16
Seattle Ridge (2400′)  21  variable  3  10
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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.