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Sat, April 14th, 2018 - 7:00AM
Sun, April 15th, 2018 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is  LOW  this morning and will rise to  MODERATE  today. Triggering a small to large wet avalanche will be possible at all elevations in the afternoon.  In the Alpine, triggering a slab avalanche 1-2′ thick remains possible where drier snow exists, and will become possible on Southerly slopes when the surface crust melts. Give cornices extra space.  

Special Announcements

The snow is melting fast at lower elevations and the following areas have been closed to snow machining on the Chugach National Forest: Twenty mile, Snow River, Primrose, Lost Lake. Snug Harbor access to Lost Lake remains open at this time. Keep an eye on the riding status at the bottom of the page for other areas.  

Be aware some summer hiking trails like Byron Glacier trail in Portage have steep avalanche terrain above them and the potential for a natural avalanche exists later in the day on slopes getting lots of sun in the afternoon.  

CNFAIC is transitioning to spring time hours in preparation for the end of the season in two weeks.  Beginning Monday, we will issue forecasts 4 days/wk on Sat, Sun, Tue, Thur. The final forecast will be on April 28th.  You can check out springtime tips on the final Summit Summary HERE.  

Sat, April 14th, 2018
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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
  • Wet Loose
    Wet Loose
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Wet Loose: Spring is here and with it comes daily fluctuations in the avalanche danger with sun and warming. Timing is everything. Clear skies overnight have created a surface crust adding strength to the snow. As the day heats up and the crust melts and loses strength, the danger rises – making it possible to trigger a wet avalanche on steep sun exposed terrain features. Today looks similar to yesterday with daily temperatures expected to reach the mid-40F’s by early afternoon and little to no wind. Remember solar noon is around 2pm  and this is when wet avalanches can begin to release, either naturally or by a person. Once the snow becomes wet and ‘mushy’ and your skis or snowmachine start trenching into wet snow, it’s time to find supportable surfaces. Even a small wet avalanche can turn into something larger in bigger terrain.

Wet Slab: There remains some uncertainty around the possibility of triggering a wet slab avalanche as warm temps today make the snow wet in the mid elevations. Earlier this week many natural wet loose and wet slab avalanches occurred below 2000′ where rain saturated the snowpack. As water drains out of the snow and we experience several days of re-freezing overnight this is becoming less likely, but not out of the question.

Cornices: Daily warming and sunnier weather can make cornices more unstable. As always, give cornices plenty of space and limit exposure underneath them.

Widespread natural wet avalanche cycle occurred below 3000′ throughout our region. Note the wet slab at 1500′ on South face of Tincan. 


Pay attention to how supportable the snow feels in the afternoon as surface crust melt and the snow becomes wet. Yesterday it was easy to post hole up to your waist on Southerly aspect below 2000′. 


Most of the large wet avalanche from 4/10-4/11 on Seattle Ridge were on the Southern end of Turnagain Pass where a generally thinner snowpack exists. Some of these avalanches released near the ground. 


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

Triggering a lingering storm slab or a persistent slab is becoming less likely with time. However afternoon warming adds an element of uncertainty as surface crusts break down and destabilize the snow on solar aspects. Yesterday a group of 3 skiers experienced a collapse (whumpf) at 3000’ on a SW aspect of Tincan, and the day before a skier triggered a storm slab on a West aspect of Johnson Pass near 4900’. We know of older weak snow (facets) buried within the top 2’ of the snowpack and we don’t have a lot of info about how this snow is adjusting in the upper elevations. Northerly aspects with dry snow (without a surface crust) may harbor this set up. Basically triggering slab avalanche 1-2’ deep should still be on your mind if venturing into steeper terrain in upper elevations.  

Sat, April 14th, 2018

Yesterday was clear and sunny and no precipitation was recorded. Temperatures reached 50F near sea level and mid 40F’s in the mid elevations. Ridgetops were in the mid 30F’s during the heat of the day. Temperatures crept into the upper 20Fs at ridge tops and mid 30F’s at lower elevations. Winds were light from the Northwest 5-15mph.  

For today expect sunny skies and another warm day. Temperatures should again reach the low 50F below 1000′ and 40F’s along ridgelines. Winds will be calm to light (0-10mph) from the NW. Temperatures are expected to be in the low 30F’s overnight.  

For Sunday and Monday sunny weather will remain with diurnal temperatures swings, cooling overnight and warming during the day . Ridgetop winds are supposed to remain light from the Northwest. There is a possibility for light rain starting Wednesday associated with a low-pressure developing near the Aleutians.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 41   0   0   68  
Summit Lake (1400′) 37   0   0   24  
Alyeska Mid (1700′) 40   0   0   65  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 31   NW   5   15  
Seattle Ridge (2400′) *N/A   NW    5 21  
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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.