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Tue, March 19th, 2019 - 7:00AM
Wed, March 20th, 2019 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger is  CONSIDERABLE  today.   Very large avalanches occurred naturally Sunday and Monday  sending debris far into runout zones and through flat areas.  Slopes  are loaded with 8 to 15 feet of snow.  Today is a break between storms. However, natural avalanches are still possible and human triggered avalanches are likely  today.   These could be very deep and dangerous and extra caution is advised.   Give cornices a wide berth. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.  

PORTAGE VALLEY:    Travel in runout zones from avalanches including venturing along and past the Byron Glacier Trail continues to be not recommended.  

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):    Large to very large human triggered avalanches remain likely. Between 2-3 feet of snow has fallen onto a very weak snowpack and avalanches are releasing in old buried weak layers.

SEWARD/LOST LAKE:    Large and dangerous natural avalanches  have been observed in this area. Today human triggered avalanches are likely in this region as well.    

Special Announcements
  • Turnagain Pass 20 years later:  On  Saturday, March 23rd from 12-2pm  swing by the Turnagain Pass moto lot and meet the CNFAIC avalanche forecasters, bring and test your avalanche rescue gear and learn about the history of Turnagain Pass and the CNFAIC. We’ll even have a few beacons buried so you can test your skills before heading into the hills!
  • Feeling sporty? Want to support avalanche education in Alaska? Head to the Alaska Avalanche School Ski-Mo (uphill/downhill) fundraiser race at Arctic Valley on Sunday, March 24th at 1pm. For more information click HERE. Great fun! Great cause!
Tue, March 19th, 2019
Above 2,500'
3 - Considerable
Avalanche risk
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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
  • Storm Slabs
    Storm Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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 the large natural avalanches kept occurring with notable avalanches observed in Crow Creek, on Tincan, Seattle Ridge, Petes North, Twin Peaks, and through Summit Lake. These had very deep crowns, and were running into the flats in many locations. This was the second day in a row of very large slab avalanches. Today is a break in the barrage of storms after 6 days of HIGH avalanche danger. Temperatures are dropping this morning but are expected to rise again this afternoon and it should be partly sunny today. The natural avalanche activity should decrease but the potential for a very large human triggered slab avalanche remains. The current snowpack needs some time to adjust to all the loading from multiple feet of snow, strong winds and rain. Be patient! We are optimistic that at some point it will stabilize but today is definitely not the day test it out.  Choose terrain very wisely. The slabs could be very deep, there may be no signs of instability and it could be the 1st or the 10th skier or snowmachine on the slope that triggers the avalanche.  Avalanches could be triggered remotely from thin spots. In addition, pay attention to solar warming and the potential for roller balls and wet loose avalanches on sunny aspects. 

Tincan avalanche. Occurred sometime between 12:15-12:25 pm. 3-18-19. Photo: Corey Anderson

 Avalanche to the ground on Seattle Ridge, 3-18-19. 

Large avalanches, Templeton – Summit Lake, 3-18-19. 


Additional Concern
  • Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Stay away from cornices. They have grown large and could be very tender and dangerous today. Triggering a cornice fall also has the potential to trigger a deep avalanche on the slope below. 

Tue, March 19th, 2019

Yesterday: Mostly cloudy skies and rain/snow showers on and off throughout the day favoring Portage and Girdwood. Temperatures were in the 30Fs and 40Fs. Winds were northeasterly 15-25 mph with gusts into the 50s. Overnight skies became broken and temperatures dropped slightly. Easterly winds decreased blowing in the teens with gusts into the 30s.  

Today:  Partly sunny skies with temperatures in the 20Fs to high 30Fs. Sea level temperatures will be around 40F. Winds will be easterly 5-15 mph with gusts into the 20s. Clouds move back in tonight and winds pick up early morning Wednesday as the next warm wet storm moves over the region. Snow should start overnight.  

Tomorrow: Mostly cloudy with rain and snow showers that could be heavy at times. Rain/snowline is forecasted around 2000′. Easterly winds blowing 20-30 mph gusting into the 50s. The warm wet pattern is forecast to continue into the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35    0     0.1     88  
Summit Lake (1400′) 37   0   0.1    30
Alyeska Mid (1700′) 34   0   0.46     78  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  25     NE   20    62
Seattle Ridge (2400′) 30   *N/A    *N/A *N/A  
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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.