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

*******************************UPDATE 2PM********************************************************

Precipitation intensity and storm totals have exceeded forecasted amounts from this morning.   Natural avalanche activity has been reported in the Girdwood Valley and south of Summit Lake.   The avalanche hazard is elevated as a result to CONSIDERABLE above treeline and MODERATE below treeline.   Natural avalanches are possible and human triggered avalanches are likely in areas that have received new snowfall amounts greater than 12″.   See below for specific avalanche concerns and areas to avoid.

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Special Announcements

Next Sunday is the  2nd  ANNUAL  CORN HARVEST  – get it on your calendar now !! Come join the CNFAIC Friends and Forecasting staff on Turnagain Pass for  free food, games, prizes, etc. This is one way we would like to thank all of you for your dedication and support. Oh, did I mention, it’s  FREE?

Mon, March 25th, 2013
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
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. Dangerous avalanche conditions. 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

In areas unaffected by wind expect to encounter enough light density snow for riders and skiers to create small to medium sized loose snow avalanches.  The only reactive snow we were able to find yesterday was a few inches of this light density loose snow.  In terrain over 40 degrees this surface snow slid readily in the form of sluffs and was low in volume and fast moving.  Expect more of the same behavior today with volumes increasing as the snow accumulates.  Human triggered sluffing has the potential to carry people into and over terrain traps.  Choose your terrain with this in mind today.

Storm Snow

New snow in the form of slabs will also be a concern.  Expect slabs up to 18″ in depth to be most sensitive on steep south facing terrain 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

Look for wind slabs to build today in the upper elevations on west and south aspects.  These slabs will be most sensitive on steep south facing terrain where a stout crust lurks beneath the surface and will provide for a good sliding surface.  We have had several reports of skier triggered avalanches mainly on south aspects over the weekend.  This setup of new snow bonding poorly to crusts primarily exists on terrain over 35 degrees.

Additional Concerns

Persistent Slab
Old wind slabs, formed by strong winds of last Tuesday are lingering below a fresh coating of snow.  These slabs are sitting on weak snow, are somewhat random in their distribution, and concealed by 2-8″ of new snow.  Because of this they are hard to detect.  Staying off of steep terrain (>40 degrees) will help to minimize your chances of finding one of these isolated pockets of slab.

Cornices
The most destructive avalanches we have seen over the past three weeks have been the result of large cornice falls.  Minimize your time on terrain with cornices sitting above and approach ridgecrests with caution.

Weather
Mon, March 25th, 2013

In the past 24 hours the mountains around Eastern Turnagain Arm on average have picked up ~6″ of new snow with .6″ of water.   Temperatures at the Seattle Ridge station at 2,400′ averaged 22.5 F.   Winds there have averaged 10 mph out of the ESE with gusts to 22mph.

Light snow continues to fall in the area and should continue through the evening hours with 6-10″ expected.   The peak intensity for snowfall will occur in the morning hours today.   Winds will pick back up later in the day and average 15-25mph out of the E.   Temperatures at 1,000′ will stay in the high teens to low 20s F today.

The extended outlook calls for clearing on Tuesday with a return to an active (snowy) weather pattern for the second half of the week.

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

Observations
Recent Observations for Turnagain Pass
Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
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11/11/23 Turnagain Observation: Tincan Common
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11/10/23 Turnagain Observation: Tincan Trees
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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.