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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, April 9th, 2014 - 7:00AM
Expires
Thu, April 10th, 2014 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a  MODERATE avalanche danger  today on all aspects above treeline  for small to medium sized loose snow avalanches and scattered 6-10″ thick wind slab avalanches. Sluffs in yesterday’s new snow should be predictable, expected and easy to trigger – on sunlit aspects, watch for these to turn to wet sluffs later in the day.  

Wed, April 9th, 2014
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
  • 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

Yesterday was a reminder of what winter can be like. We ended up with 6-8″ of very low density powder snow. Though it was enough to blanket the many tracks put down over the past month, it wasn’t quite enough to keep your skis/board or sled off the old hard surfaces underneath. Today we have a fight to return to spring as the sun is expected to shine but the temperatures look to remain cold.

How much the sunshine is able to warm the new snow will be the main concern for today. Despite cold temperatures, if the wind remains light we can expect wet point release avalanches to occur on East, South and Westerly aspects as the sun makes its rounds. Watch for these to release both naturally from rocks and trees as well as be easy to initiate yourself (as seen in this VIDEO from yesterday). These could become fairly large on sustained slopes as all the new snow will likely be entrained on the way down. Dry sluffs on Northerlies or areas the snow remains cold should also be expected.

Wet or damp sluffs are much harder to get out of and can push you around much more than dry sluffs due to the heaviness of the debris. This is one of those predictable and easy to manage avalanche issues if you are aware of your terrain. Getting run over by a wet sluff in a confined gully can become a serious issue.


Garden variety new snow sluffs from yesterday – this will likely be the case again today:

 

Avalanche Problem 2
  • 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

Although winds were calm at many weather stations yesterday and overnight, the gap winds did blow strong up Turnagain Arm (from the West). Seattle Ridge weather station can feel some of these and had a few hourly averages near 15mph during the past 24-hours. Additionally, wind may bump up a bit today – enough to move a little snow around on the ridgelines. The new snow is so light that it won’t take much to form soft wind slabs. If you are in one of these more windy locations, watch for cracking in the snow around you and surface clues that wind has formed slabs. These should be shallow and soft but also could have enough volume to be a problem if you are in larger terrain and significant snow is entrained.

Weather
Wed, April 9th, 2014

Yesterday turned out to feel quite winter-like with 6-8+” of new snow, cold temperatures and mostly obscured skies. During the past 24-hours we have seen temperatures average in the low teens on the ridge tops and the mid 20’sF at 1,000′. Winds have been very light from the Northwest averaging 3-5mph, the exception is along Turnagain Arm mentioned above.

Storm totals at treeline are:
   Turnagain Pass:  6-8″
   Summit Lake:  1″
   Girdwood Valley:  6-8″

For today, skies should clear this morning and the sun will be out as a high pressure builds over mainland Alaska. Temperatures have plummeted to the single digits on the peaks overnight but should rebound a bit with daytime heating. Winds are slated to pick up slightly from the Northwest to the 10-15mph range.

Thursday and Friday the high pressure remains with sunny skies on tap. However, for the weekend it looks like another low pressure may move through.

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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.