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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, April 2nd, 2019 - 7:00AM
Expires
Wed, April 3rd, 2019 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

Warm temperatures and direct sunlight will increase the avalanche danger from  LOW  this morning  to MODERATE by this afternoon/evening. Human triggered wet loose avalanches on steep, solar aspects, especially above 3000′, are possible once the sun softens surface crusts and weakens the snowpack. Avoid being under glide cracks and give cornices an extra wide berth!  

PORTAGE VALLEY:    Summer trails with avalanche terrain overhead, such as Byron Glacier Trail and Crow Pass, are still not recommended in the afternoon or evening due to the possibility of an avalanche occurring above.

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):   Human triggered slab avalanches remain possible in upper elevation terrain on all aspects. This area has a thin  snowpack with many weak layers. High elevation sun-affected slopes are the most suspect for triggering a slab.

SEWARD/LOST LAKE:   Similar to the Turnagain Area travel on solar aspects should be carefully evaluated later in the day and travel under glide cracks should be avoided.

Special Announcements

Help track snow depth and WIN PRIZES too! The  Turnagain Pass Spring Stash Collection Contest  ends April 15th and the community needs your help!

Tue, April 2nd, 2019
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
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Yesterday was slightly cooler than the day before and overnight temperatures were cooler than the past couple nights. Clear skies promoted a solid freeze overnight.  The snowpack has already seen many days of a springtime melt-freeze pattern in the low and mid-elevations. Overall the possibility of natural wet loose and wet slab avalanches has decreased. However, there is still the potential for person, on skis or a machine, to trigger an avalanche in the afternoon/evening on solar aspects as the crust breaks down and slopes get soft and punchy. This is heightened in the Alpine where the warming of the surface snow is more recent.

A safe day in the mountains includes planning ahead. Know the terrain you are traveling on and under and if it will be affected by the sun. The avalanche danger on steep slopes on the southern end of the compass will increase this afternoon/evening. Play the aspects for the best conditions and to stay safe. The boot test is a great way to assess how the daytime warming is, or is not, affecting the surface. If your boot easily sinks into mushy wet snow, it’s time to get onto shaded slopes or off the one you are on. Wet loose avalanches can start small from a person pushing soft wet snow as they ski or ride. If the terrain is large enough, this small slide can entrain snow and turn into a large and unmanageable avalanche.

CORNICES: Cornices are very large and direct sunshine will destabilize them. A cornice fall still has the potential to trigger an avalanche on the slope below and could break farther back than expected.


Snowmachine triggered wet loose avalanche on to the uptrack on Friday, 3-29-19. Photo: Sean Fallon


 Cornice over Warm up bowl, 3-30-19. Photo: Graham Predeger. Give cornices a wide berth. 


Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Glide cracks are appearing throughout the advisory area and have been avalanching daily. Yesterday was the first day without notable activity reported but the message remains the same. Avoid traveling under glide cracks at all times of the day!  Remember, glides can release even if a hard surface crust is present (unlike the wet loose and wet slab avalanche problems). Many cracks are opening up in popular terrain and keep an eye out for them.  Glide avalanches are full depth avalanches that have the potential to very dangerous.

Glide avalanche South side of Wolverine, observed 3-30-19.

Glide avalanche Lynx creek, witnessed in motion on 3-29-19.

Weather
Tue, April 2nd, 2019

Yesterday: Sunshine and clear skies with temperatures in the high 30Fs to mid 40Fs. Winds were light and westerly. Overnight temperatures dipped into the 20Fs and mid to low 30Fs. Skies were clear and winds increased slightly overnight gusting into the teens.

Today: More sunshine and clear skies with temperatures in the 30Fs in the Alpine and 40Fs at lower elevations. Winds will be westerly 5-10 with gusts into the teens. Overnight skies will be partly cloudy and temperatures are forecast to decrease into Wednesday as cooler air moves over the region.

Tomorrow: Clear and sunny again with cooler temperatures and light winds. There is still some uncertainty about the precipitation potential on Thursday and Friday but expect clouds and a chance of rain/snow showers.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 39 0 0 66
Summit Lake (1400′) 34  0  0 22
Alyeska Mid (1700′)  40 0 0 59

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 32 W  3  13
Seattle Ridge (2400′)  37  W  1  4
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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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