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ARCHIVED - Forecasts expire after 24 hours.
Mon, February 25th, 2013 - 7:00AM
Tue, February 26th, 2013 - 7:00AM
John Fitzgerald
Avalanche risk The Bottom Line

The avalanche hazard is MODERATE above and below treeline today.   Above treeline be on the lookout for fresh wind slabs that will be sensitive to the weight of a person or snowmachine.   Below treeline new slabs that formed over the weekend sit on a crust that have the potential to produce avalanches.

Mon, February 25th, 2013
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
  • 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

In the upper elevations winds have been consistently blowing in the upper teens to low 20s out of the East.  Expect to encounter wind slabs up to 18″ in depth today in starting zones.  While the new storm snow that fell over the weekend has in general bonded well to old surfaces, the simple act of windloading can and will create areas of unstable snow.  Continued winds out of the East today will help to increase the size of these slabs.  Be on the lookout for snow that looks smooth, rounded and pillowy.  These areas will be most sensitive while the snow is being transported and slabs are forming.  While the predominant wind direction is out of the East, localized winds will blow in a variety of directions.  With this in mind it is important to recognize wind and loading patterns and stay off of slopes that have been recently loaded.

Avalanche Problem 2
  • 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 crust that formed prior to the weekend has shown to be a problem in some areas.  Yesterday my partner and I found weak snow just below this new crust to be reactive and unstable in the lower elevations.  While this is not a widespread problem, it is worth paying attention to, especially if you experience collapsing/whoompfing as we did yesterday.

Deeper weak layers that were reactive in tests and have produced several avalanches over the past two weeks have not shown to be a problem recently.  A mid elevation crust (~1,500′-3,000′) with weak snow above, and the old weak snow at the ground have been the two layers we have been tracking.   Despite a lack of activity at these layers it is still worth keeping them in mind as they have the potential to re activate in areas where the snowpack is more shallow.

Mon, February 25th, 2013

Over the past 24 hours the mountains have picked up to 3″ of new snow in the Girdwood Valley, with lesser amounts on Turnagain Pass.   Winds have averaged 15 mph out of the East and temps have been in the high teens F at 3,800′ and around 32 F at sea level.

Today we should expect to see light snow showers picking up later in the day as another weak low pressure system moves over the forecast area.   Ridgetop winds will blow 20-30 mph out of the East and temps at 1,000′ will be in the mid twenties.

The extended outlook calls for more of the same, as an active weather pattern continues to bring modest amounts of snow to the area.


Wendy will issue the next advisory tomorrow morning, February 26th.

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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.