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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, April 11th, 2016 - 7:00AM
Expires
Tue, April 12th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

Below 2500′ the avalanche danger is  CONSIDERABLE  today due to a continued pattern of warm temperatures, rain and an active glide avalanche cycle. Natural wet loose avalanches in steep terrain are possible and human triggered wet loose avalanches are likely.  Avoid being under the runout of glide cracks.

In the Alpine the avalanche danger is MODERATE. Human triggered wind slabs are possible on leeward slopes and cornices remain a hazard along ridgelines. If there are extended periods of sunshine today the danger may rise to CONSIDERABLE in the Alpine.

***Travel is not recommended in avalanche terrain on the West (motorized side of Turnagain Pass).

If you are headed to the Summit Lake area don’t forget to check  Summit Lake Summary.    

Special Announcements
  • This will the final week of  daily  avalanche advisories. Between Monday, April 18th and Saturday, April 30th we will be issuing advisories on weekends and intermittently during the week.

  • The Chugach National Forest has closed some riding areas to motorized use due to snow melting out. Please see the table at the bottom of this page for a complete list. Snug Harbor, Summit Lake and  Turnagain Pass (N. of Granite creek)  will remain open.  
Mon, April 11th, 2016
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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
  • Announcement
    Announcement

After driving through Turnagain Pass yesterday and observing the state of Seattle Ridge and the uptrack, travel in avalanche terrain (including runout zones) on the motorized (West Side) is not recommended. The snowpack below 2500′ is saturated; there is natural wet loose activity and a very active glide avalanche cycle going on. Unfortunately there really isn’t a way to negotiate a route to the ridge without being in danger. Seattle Ridge is literally falling apart. Essentially the hazard is HIGH on this side of the pass. Until we get a very hard freeze, the glide avalanche cycle completely ends or all the snow in the starting zones that threaten the uptrack avalanches, traveling here is like playing Russian Roulette. 

Glide avalanche hazard also exists on the non-motorized slide. Travel underneath existing glide cracks is not recommended. In addition, be on the lookout for new glide cracks forming. 

Avalanche Problem 2
  • 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

Natural wet loose avalanche activity was observed yesterday and may continue today. Overnight there has been a slight cooling trend with mid elevation temperatures dipping below freezing. This may cause a superficial freeze and thin crust. However if the sun comes out, more rain falls or the temperatures climb, human triggered wet loose avalanches will continue to be likely in steep terrain below 2500′ and natural wet loose avalanches will be possible. 

If the snow feels punchy, unsupportable or slushy and you find yourself sinking in on your skis or snowmachine it is time to get off the slope. 

 

Additional Concern
  • 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 Alpine new snow and wind have likely formed wind slabs on steep leeward slopes. Yesterday there was evidence of blowing snow and wind effect. The fresh wind slabs may be quite tender along ridgelines and on unsupported terrain. There is potential for a little more snow today and easterly winds. Look for cracking and remember warm temperatures and sun can make these slabs even more touchy. 

Cornices: This hazard continues to loom along ridgelines in the Alpine and may be triggered by the weight of a skier or a snowmachiner. These may also fall naturally with additional snow/wind loading or rapid warming. Remember these break farther back than expected and travel on or underneath should be avoided. 

Wind plumes on Sunburst yesterday. photo: Joe Kurtak

Weather
Mon, April 11th, 2016

Yesterday was mostly cloudy to partly sunny with rain/snow showers and gusty easterly winds. Temperatures were in the mid 20Fs to mid 40Fs depending on elevation.  

Today will be mostly to partly cloudy with rain/snow showers and a possibility of sun. Temperatures will be in the mid 20Fs to low 40Fs. Winds will be easterly 10-25 mph.  

For Tuesday there looks to be a break in the showery weather with clearing skies as a ridge of high pressure moves over the region. There is another low moving into the Gulf that will most likely put us back into the moist pattern of scattered showers later in the week.  

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  35  0  0* 114  
Summit Lake (1400′)  37 0    0  32
Alyeska Mid (1700′)  34 0    .5  100

*Center Ridge maybe under reporting, data has been wonky for the past two weeks

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  26  ENE  18  51
Seattle Ridge (2400′)  29  SE 20*    38

*Seattle Ridge did not record winds from 5 am-10 am yesterday.

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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.
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