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Sat, February 8th, 2014 - 7:00AM
Sun, February 9th, 2014 - 7:00AM
Kevin Wright
Avalanche risk The Bottom Line

If you haven’t been watching the weather closely you may have missed the storm that happened on the Kenai yesterday.  Snowfall was somewhat localized with both Seward and Girdwood only getting a little snow.  Turnagain Pass came out as a big winner from this one.  By 2pm yesterday there was a confirmed 10 inches at the road.  Center Ridge snotel site is now reading a 16 inch increase in snow depth from yesterday.  

The snow came in cold and dry with some wind.  Windslab is the primary reason that pockets of  CONSIDERABLE  may be found at any elevation where wind was transporting the new snow.  We can expect soft wind slab sliding easily on the old firm crust surface.  Avalanches occurring from the new snow should be low volume and have relatively little force.  

Anywhere the wind slab is not present, sluffs may be initiated on steep terrain in the new storm snow.  Underneath the new snow we still have the old deep slab concerns that have kept us at a  MODERATE danger rating recently.

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Sat, February 8th, 2014
Above 2,500'
3 - Considerable
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
  • 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

Fresh wind slab from yesterday’s storm is the most likely problem to find today.  This should be a manageable avalanche concern – not dangerous unless you jump into high consequence terrain without sluffing out the run first.  I expect a lot of slopes will be easily triggered by skiers today, but this is light density snow and should behave in a predictable manner.  It’s the perfect scenario for controlled ski cutting (in areas of safe terrain exposure).  The CONSIDERABLE danger rating is for likely human triggered avalanches – of small size, in many areas.

The good skiing will probably be sheltered areas where wind didn’t have a lot of effect.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
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.
More info at Avalanche.org

We’ve been tracking multiple buried weak layers for quite some time.  The big meltdown in January caused many large deep slab avalanches, but since cooler temperatures took over, the mountains have gone dormant.  We still have some concerns about the persistent weak layers (persistent means they stick around for a long time).  The areas of greatest concern include elevations above 3500 feet where the rain and warm temperatures had less effect on the snowpack.  It may still be possible for a person to initiate a collapse and trigger a deep avalanche.  

This is a MODERATE type concern of low likelihood but higher consequence.  

Sat, February 8th, 2014

The big news in the weather history is the storm that blew through yesterday.  Areas hardest hit by this storm appear to be glacier regions of the southeast Kenai peninsula, Prince William Sound, Turnagain Pass (16 inches?)  and Grandview (10-12 inches).  If instrumentation is reading correctly, snow density is somewhere around 5%, or very light dry powder.  Wind at the ridgetops was blowing 40s-60s mph on Sunburst  from an ENE direction.  Temperatures during the storm started cold, in the teens and low 20s and rose to what they are currently (mid to high 20s).

Today – mostly cloudy skies, temperatures in the 20s, and a light NW wind.  

Weather trend looks to be colder and windier from the north going into next week.  No major storms are on the horizon for the coming week.

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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.