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Tue, March 27th, 2018 - 7:00AM
Wed, March 28th, 2018 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger continues to be  MODERATE  above 1500′ on all aspects. Triggering a hard slab avalanche 2-4 feet thick remains a possibility. These hard slabs can be remotely triggered from the side or below. Additionally, watch for old wind slabs in steep rocky terrain and give cornices a wide berth.  

Similar avalanche concerns exist in the Summit Lake area  and other zones on the Kenai.

Tue, March 27th, 2018
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
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
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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

Triggering a hard slab avalanche is still our primary concern in the backcountry despite the quiet weather. It has been over two weeks since the last snowfall event and four days since the last human triggered avalanche; yet with the hard-pack surface conditions, there haven’t been many folks out lately testing the slopes. Hiding under the snow surface are weak layers in the snowpack that just will not go away. However, with time they are becoming more and more difficult to trigger, trending toward unlikely. Hence, we are in a low probability, high consequence situation. The tricky part about this is, the pack appears to be stable but the chance remains for an unmanageable and destructive avalanche if a person hits just the wrong spot. 

To recap, the weak layers in question were formed back in January. They are facets sitting on a slick melt/freeze crust at the mid elevations and facets mixed with buried surface hoar at the upper elevations. The slab on top is 2-4′ thick and very hard due to a strong Northwest wind event that ended last Thursday. This wind event caused unusual loading patterns avalanches could be triggered in unexpected places for those with a lot of familiarity of the area.

With sunny skies forecast later this week and partly cloudy skies today and tomorrow, there is little in the way of weather that will impact our old and tired snowpack – except for the sun. We can’t forget that spring is here; even though temperatures have been relatively cool, this could change any day now. Many folks are taking advantage of the snow conditions by long tours and exploring. If this is the case, know that triggering a slab from the flats below a slope is possible. Being aware of runout zones and considering how far an avalanche could send debris should be in the forefront of our minds. Additionally, no obvious signs of instability may be present before a slope releases and it may be the 10th skier or snowmachiner onto a slope that finds a trigger point. 


Goat Mountain and Goat Couloir pictured below with some old debris down the main chute. There is also what could be newer debris from last weekend coming from steep rocky terrain out of sight on the looker’s right. Springtime is here and as rocks warm with the sun, wet loose and wet slab avalanches should be on our radar. We don’t want to be in the path of even a small wet slide.


Seattle Ridge – this Southeast facing terrain (that faces the Seward Hwy) is one of the first areas to have wet avalanches during the onset of the spring warm-up. So far the snow remains cold and crusty, but this could change quickly if sun and warm temperatures arrive this week. 




Other avalanche issues to keep in mind: 

Wind Slabs:  Old hard wind slabs are sitting on a variety of aspects due to prior unusual loading patterns. Watch of these slabs to possibly pull out in steep rocky terrain where slabs are unsupported from below. This type of terrain (steep unsupported slope) is also suspect for triggering a deeper slab mentioned above. 

Cornices: Many cornices are quite large and teetering over. Temperatures have been cool lately but as we head into warmer, sunnier weather remember this can help de-stabilize them. As always, give cornices plenty of space and limit exposure underneath them.

Wind effect on the Seattle Ridge headwall. Note the cross loading above the rocks on the slope in the back, this is an example of loading on ‘unsupported’ slopes.

Wind effect in the Seattle Creek drainage (photo: Troy Temple)

Tue, March 27th, 2018

Partly cloudy to overcast skies were over the region yesterday. Ridgetop winds were moderate from the East (15-20mph) before decreasing to light and variable overnight. Temperatures hovered near 20F along ridgetops and warmed to the low 30’sF at 1,000′ with daytime warming before cooling into the mid 20’s overnight.

Today, Tuesday, partly cloudy skies are on tap. It’s one of those days where the sun could shine more than expected before thicker clouds move in overnight. Ridgetop winds will be generally light from a Westerly direction (5-10mph). Temperatures look to remain near 20F along ridgetops and could warm to the mid 20’s with daytime warming. Valley bottom temperatures are in the teens this morning and should warm to the low 30’sF.

Wednesday morning, cloudy skies with a chance for a few flurries are expected as we sit on the outskirts of a low-pressure system rotating in the Bering. By Wednesday evening through the rest of the week, high pressure builds in bringing sunny skies. So far, the winds associated with the clear skies look to remain light and Northerly.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   0   0   78  
Summit Lake (1400′) 27   0   0   31  
Alyeska Mid (1700′) 29   0   0   72  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 18   NE   13   35  
Seattle Ridge (2400′) 24   E   11   36  
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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.