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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, April 17th, 2016 - 7:00AM
Expires
Mon, April 18th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

A  CONSIDERABLE  avalanche danger remains  on all slopes under 2,500′ in elevation  due to an active glide avalanche cycle. Destructive glide avalanches are occurring daily across the region.  Avoid being under the runout of glide cracks.  In addition to glide avalanches, natural wet loose avalanches are possible and human triggered likely in steep terrain that harbors wet and saturated snow.

In the Alpine the avalanche danger is generally  LOW. Watching for lingering wind slabs, cornice falls and human triggered wet loose avalanches.  

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

AVALANCHE OUTLOOK for Monday, April 18th:  

Monday looks to be very similar to today. In general all the avalanche instabilities that have been mostly confined to the 1000′-2500′ elevation band may slowly creep into the Alpine as the temperatures remain warm and the sun shines during the day. Pay attention to changing conditions. The hazard may increase to MODERATE in the Alpine.

Special Announcements
  • We now will be issuing advisories 5 days a week until our final advisory on Saturday, April 30th.   Advisories will be posted at 7 am each day except Mondays and Wednesdays.
  • We are finished publishing weekly summaries for the Summit Lake zone. Please see the final  Summit Lake Summary and springtime tips  on this link. Reminder: as the season winds down, we will continue to publish all reports/observations sent in to us!
Sun, April 17th, 2016
Alpine
Above 2,500'
1 - Low
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
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Yesterday at least one new glide avalanche was observed. What was most notable was that new cracks continue to appear and grow. The West facing terrain on Cornbiscuit now is littered with small, progressing cracks that make it essentially un-skinnable. Magnum West face and South face both have growing cracks and even Sunburst’s “mini” glide crack is getting more pronounced. This all indicates snow on the move. Pick your route carefully in the 1000′-2500′ elevation band.

This current wet snowpack, combined with mostly sunny skies and temperatures above freezing, has us continuing to think glide activity is likely. Our message remains the same: AVOID being under glide cracks and respective runout zonesTo be in the wrong place at the wrong time when a glide releases could likely be deadly. Considering the motorized up-track is threatened by cracks, we are recommending that people do not travel on the up-track or in runout areas along Seattle Ridge.

Cornbiscuit  glide cracks. 4/16

 

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

Wet loose avalanches have been occurring for the past few days. These have been naturally occurring with warm temperatures, rain and direct sunlight affecting surface snow and mostly confined to the 1000′-2500′ elevation band. Expect more of the same today and potentially an increase with clearing skies. The few inches of new snow that fell over the past few days above 2000′ is primed if heated enough and lower elevation snow is completely saturated. Human triggering a wet loose avalanche in steep terrain is likely. Pay attention to ski penetration and punchy snow as well as roller balls both natural and travel initiated. Remember wet loose avalanches can be hard to escape once initiated and particularly hazardous if they push you into a terrain trap. Take into account what terrain is above you and what you may have to cross under to get back to your car when venturing to cooler snow in the Alpine.

Wet loose activity on Seattle Ridge with glide cracks and old glide avalanches. 

 

Additional Concern
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

At elevations above 2,500′ and in the Alpine the snowpack is generally stable. There are a few things to watch for if traveling in the upper elevations:

– Lingering wind slabs that could be triggered in steep, unsupported terrain. 

– Cornice falls (we have yet to see cornices start falling in the Alpine but this could happen any day with the warm temperatures and direct sunlight).

– Wet loose avalanches on steep solar aspects, both natural and human triggered. These have been predominantly confined to the 1000′-2500′ elevation band but this may change and be higher with heating throughout the next two days.

 

Weather
Sun, April 17th, 2016

Yesterday was mostly cloudy in the morning with isolated rain and snow showers trending to partly cloudy by mid afternoon. Temperatures were in the upper 20Fs to upper 30Fs. Winds were light and easterly.

Today and tomorrow are forecasted to be mostly to partly sunny with temperatures in the high 30Fs at 3000′ and the high 40Fs at 1000′. Winds will be light and variable. Scattered showers will be a possibility Monday afternoon with increasing clouds and precipitation on tap for Tuesday.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  36  0 0   110  
Summit Lake (1400′)  37 0    0 27  
Alyeska Mid (1700′)  35  0 .1    95

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 30    ENE 10   20  
Seattle Ridge (2400′) 29   SE   15   28  
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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.