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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, January 19th, 2017 - 7:00AM
Expires
Fri, January 20th, 2017 - 7:00AM
Forecaster
Heather Thamm
Avalanche risk The Bottom Line

There is a MODERATE  avalanche danger in the Alpine where triggering a fresh wind slab on leeward terrain is possible and in protected steep areas  loose snow avalanches could be fast moving and run further than expected.  At Treeline and below the avalanche danger is LOW  where triggering an avalanche is unlikely.  

***Placer and 20 Mile opened yesterday and there is limited information about the snowpack in these areas. Approach terrain with a cautious mindset and be  on the lookout for Red Flags like recent avalanches, shooting cracks and collapsing. Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!!

***In the Girdwood Valley where 2.5′-3′ of snow fell this weekend, twice as much as Turnagain Pass, heighten avalanche conditions exist.  Triggering a persistent slab 3+ feet thick or a larger is possible in Girdwood and should warrant extra caution!!!

Special Announcements

Placer area  and 20 Mile are now OPEN to snowmachining.  Please reference the bottom of this page for the latest snowmachine area openings on the Chugach NF.  

Join CNFAIC for our final Fireside Chat TONIGHT, Jan 19th! Aleph Johnston-Bloom will discuss how the current Turnagain area snowpack has developed over the winter, understanding the different avalanche problems described in the advisory and how to use them in decision-making.  – Details  HERE.

CNFAIC will be hosting a FREE avalanche rescue workshop in Turnagain Pass on Saturday, Jan 21st, at the motorized parking lot, 11-12:30am. This is a great opportunity to practice companion rescue with your beacon, shovel and probe and your partners and get a little feedback. This workshop is open to everyone and anyone, novices and experts, that recreate in avalanche terrain €“ snowmachiners, skiers, kicker-builders, etc!! More details HERE.

Thu, January 19th, 2017
Alpine
Above 2,500'
2 - Moderate
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. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. 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
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

Yesterday Moderate Northwest ridgetop winds were seen blowing snow throughout our region loading many South and East aspects. Plenty of snow was available for transport and fresh wind slabs 1-2’ deep could be tender today. Steep, unsupported, leeward slopes in the alpine are the most suspect and a slab could break above you. Be on the lookout for drifted snow that has a pillow shaped appearance and don’t be surprised if slopes are loaded further down hill than expected. Evaluate the snow as you travel by testing small slopes and avoid high consequence terrain where the snow feels stiff, supportable or hollow sounding. Shooting cracks will be obvious clue that the snow is unstable. 

In Girdwood wind slabs may be thicker and could step down to an older weaker layer below. More caution is advised in this area.

Blowing snow along ridgetops was observed throughout the region yesterday, including the Placer Valley as seen below. Photo by Conrad Chapman. 

 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Today in areas protected from the wind triggering a loose snow avalanche will be possible on steeper slopes. Fast moving “sluff” could entrain snow, run further than expected and easily knock you off your feet. Manage this problem by letting the snow move past you and choose terrain that doesn’t have high consequences if you fall. Although it is unlikely to bury a person, keep in mind that larger terrain will have more volume. Cold temperatures could increase this problem throughout the week as the surface snow becomes even less cohesive. 

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

A variety of weak layers exist within the snowpack and vary across our region. Following the most recent snowstorm (1/13-1/16) most of the avalanche activity has been observed in the Girdwood Valley. This makes sense since this storm favored this area and left 2-3’ of snow. A handful of small, but deep (to the ground) avalanches were spotted in the alpine yesterday on Southern aspects of Penguin Ridge, Raggedtop, and Magpie. It is unconfirmed if these all happened as a result of moderate NW ridgetop winds that started yesterday morning or if these happened near the end of the storm on Monday (1/16.) Either way triggering even a smaller persistent slab could bury a person or take you for a very unfavorable ride over rocks. If you see recent avalanche activity, experience shooting cracks, or “whumpfing” these are obvious clues that you should avoid steep slopes.

If traveling in the Placer and 20 mile zone, where we have little information about the snowpack, use caution if venturing into steep untested slopes. An observation yesterday confirmed significant wind transport along ridges in this area and there is also a possiblity of triggering a slab on an older deeper layer of the snowpack. It always advised to ride slopes one at a time, have a escape route planned, watch your riding partners and avoid terrain traps like steep gullies. Ease into terrain and let us know if you see an signs of instability today. 


Recent avalanche activity in the Crow Pass area on South aspects of Magpie. More photos of recent avalanche activity in Girdwood Valley can be found HERE.

 

 

Weather
Thu, January 19th, 2017

Yesterday skies were clear and temperatures hovered between 0F to -5F. Northwest winds bumped into the 20-35mph range along ridge tops and remained moderate overnight. No new precipitation was recorded.  

Today looks similar with temps around 0F and another day of clear skies. NW winds will continue to blow 10-20mph, but should decrease by late afternoon to 5-15mph range.

Tomorrow expect a slight increase in temperatures (15F) and a possibility of scattered snow showers. There is talk of the cold arctic over Southcentral, AK breaking up as low pressure tracks into the Gulf late this weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) -2   0   0   42  
Summit Lake (1400′) -9   0   0   14  
Alyeska Mid (1700′) -2   0   0   40  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) -4   WNW   10   32  
Seattle Ridge (2400′) -1   W   14   53  
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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.