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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, April 27th, 2014 - 7:00AM
Expires
Mon, April 28th, 2014 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

UPDATE (Tuesday morning): On Monday a slab avalanche was triggered  in Tincan’s North facing chutes. It released when the  second snowboarder entered the chute. The slab was reported to be 1-2′ thick and entrain heavy wet snow, depositing a large debris pile. More details and photos coming soon.

There is a MODERATE avalanche danger for wet snow avalanches at elevations below ~3,000′ and on sunlit slopes at the upper elevations. Human triggered, and potentially natural, wet loose and shallow wet slab avalanches containing Friday and Saturday’s 8-12+” of heavy snow are possible with today’s warming.

Additionally, there is a MODERATE danger in the steep upper elevation terrain where 1-2′ thick wind slabs will be possible to trigger. Cornices have grown and continue to deserve a wide berth from both above and below. Cornice falls will have the potential to trigger avalanches.

Avalanche Outlook for Monday and Tuesday:  Possible natural and human triggered wet avalanches are the main concern at all elevations with daytime warming and forecast sunshine. See below for more details.

Special Announcements

–  Today is the FINAL forecast for the 2013/14 CNFAIC winter season. However, it does not mean that avalanche season is over. We will continue to post observations sent in to us through the spring and early summer.  

–  Yesterday was the 2014 CORN HARVEST. A big Thanks to everyone who stopped by despite the rain and wind!! Also, thanks to the  Friends group  for making this event happen. Good times, free food and raffle prizes for many.

                                                                               

Sun, April 27th, 2014
Alpine
Above 2,500'
2 - Moderate
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. 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
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

The mountains around Turnagain Pass, Portage Valley and Girdwood Valley got a healthy dose of new snow during the past 48 hours. We have seen between 10 and 20 inches of new medium density snow at the high elevations and around 6-10 inches of wet snow below treeline. There was little visibility yesterday but we did see one wind slab and initiate a few wet sluffs in steep terrain. See video below.

The main concern for today, and heading into Monday and Tuesday, will be how this new snow sheds off the slopes with our spring-time weather. As the sun comes out and warms the surfaces, especially at the upper elevations, watch for wet slabs and potentially large point releases to initiate. Expect wet slab depths to be in the 10-20″ range and point releases to entrain all the new snow. These types of avalanches can be very unmanageable due to the heaviness and momentum of the debris.

Cornices:
Cornices formed during the storm are suspect for breaking off in the next couple days. Not only are they a concern alone, but they will have the potential to trigger wind slabs or wet avalanches below.

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

The strong Easterly winds that have been relentless for two days now will slowly begin to decrease through today. Ridgetops are expected to average in the 25-35mph range which will be enough to continue loading slopes. Yesterday, wind was making it well into the trees and forming slabs above 2,000ft; below 2,000ft the snow was too wet for the wind to transport. We saw one natural cornice fall that triggered a wind slab off the CFR ridge on Tincan (~2,500ft elev. SW aspect) – nothing too surprising with 10″ of new snow at that point and strong wind.

For today, wind slabs and drifts will be found at the upper elevations. These are likely to be fairly stubborn to trigger due to the higher density ‘stickiness’ of the new snow. However, they are 1-2ft thick (possibly thicker), dense and would be hard to get out of if released. Letting the new snow settle out a day isn’t a bad idea if you are headed to large or committing terrain. Keep in mind that these wind slabs can re-activate during the first day to two of intense sun and warming – possibly today, Monday or Tuesday.

A look at yesterday’s conditions during the height of the storm:

 

Weather
Sun, April 27th, 2014

A wet, warm and windy storm continued to impact the mountains yesterday. Skies were obscured and rain fell below 1200ft with wet snow above, becoming drier with elevation. Winds were out of the East averaging 30-40mph with gusts to 71 at the Sunburst weather station. Temperatures have held steady in the mid to upper 20’s F on the ridgetops and upper 30’s F at 1,000ft.

Mid elevation snow totals:
                                                  Last 24 hours            Storm Total (beginning Friday morning)

Center Ridge SNOTEL (1880ft)       4″ (.7″ water)               12″ (1.5″ water)
Alyeska Mid (1700ft)                       1″(0.2 water)                 7″ (.9″ water)
Summit Lake (1400ft)                      2″(.3″ water)                 2″ (.3″ water)

Today, Sunday, this system will slowly move out and cloud cover should break a bit. There is still .1-.2″ of rain expected below 2,000′ with 1-2″ of snow above treeline. Ridgetop winds are forecast to remain from East in the 25-35mph range and temperatures warm to 45F at 1,000′ and up to the 30’s F on the ridgelines.

For Monday and Tuesday we should see a return to partly cloudy skies and warm spring-time temperatures.  

Observations
Recent Observations for Turnagain Pass
Date Region Location
03/28/24 Turnagain Observation: Sunburst
03/27/24 Turnagain Observation: Tincan Trees
03/26/24 Turnagain Observation: Cornbiscuit
03/25/24 Turnagain Observation: Tincan
03/22/24 Turnagain Avalanche: Magnum Northwest Aspect
03/21/24 Turnagain Observation: Sunburst
03/21/24 Turnagain Observation: Tincan Proper North Aspect
03/20/24 Turnagain Avalanche: Seattle Creek Drainage
03/19/24 Turnagain Observation: Tincan CFR
03/18/24 Turnagain Avalanche: Tincan – Eddies – Seattle Ridge
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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.