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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, March 9th, 2024 - 7:00AM
Expires
Sun, March 10th, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations today. Human triggered avalanches are still possible on a weak layer of facets buried by 1-2′ of new snow on Tuesday night. We recommend carefully evaluating how well the new snow is bonding to the old snow surface before committing to steep terrain. To avoid this problem entirely stick to lower angle slopes. Smaller loose snow avalanches are likely on steep terrain, either on northern aspects where dry snow remains on the surface, or on southern aspects that could heat up if the sun comes out today.

SUMMIT/JOHNSON PASS: The snowpack in the central Kenai mtns is weaker than at Turnagain. Check out the weekend outlook for Summit Pass and Seward for more information.

Special Announcements

It is with a heavy heart that we share the loss of two avalanche professionals from the Pacific Northwest this week. Nick Burks, who was a forecaster for the Wallowa Avalanche Center died in an avalanche accident while skiing with a friend on Wednesday, March 6. Matt Primomo, who was an avalanche forecaster for the Northwest Avalanche Center, died in a non-avalanche related accident on Thursday, March 7. Our thoughts are with our friends down south – their friends, families, and to the communities which these people were such a major part of.

Sat, March 9th, 2024
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
Sun, March 10th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Sun, March 10th, 2024
Alpine
Above 2,500'
3 - Considerable
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.
Recent Avalanches

Several new avalanche observations came in yesterday from the Portage and Skookum valleys, but as far as we know they were all avalanches that released earlier in the week. Likely most of them released naturally during the quick hitting storm on Tuesday night into Wednesday. There is a concerning pattern of avalanches releasing with much wider start zones than typical, which is a strong indication of a persistent weak layer.

Natural avalanche near Explorer Glacier that likely released during the storm on Tuesday night. Photo from Emily Sullivan 3.8.24

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

The storm that brought about 1′ of new snow to Turnagain Pass and closer to 2′ of new snow to Placer Valley on Tuesday night buried a weak layer of facets. At elevations below about 2000′-2500′ there is an icy crust which formed on Presidents Day associated with the layer of facets, which has caused avalanches failing on this layer to release much wider than normal, connecting multiple terrain features and creating large avalanches. Due to the icy crust at these lower elevations this layer of facets is likely to remain unstable for longer than normal and could produce additional large avalanches. Above 2500′ the new snow fell onto a mix of firm wind affected and softer snow surfaces, which initially did not bond well with the new snow. We are uncertain how long the instability at the interface with the new snow from this week will last at upper elevations.

It has been three days since the last storm, so the snowpack should be adjusting to the new snow load, making human triggered avalanches 1-2′ deep less likely. However, persistent weak layers can remain unstable for longer than normal and cause large avalanches without obvious warning signs. We recommend carefully evaluating how well the new snow is bonding to the old snow surface before committing to steep terrain.  Since the weak layer is only buried 1-2′ deep right now, using hand pits and jumping on test slopes are still viable options to evaluate the interface with the old snow surface. If you want to avoid this problem entirely we recommend sticking to low angle slopes.

Dry loose avalanches (aka sluffs) are very likely on steep sheltered terrain today, especially on the northern end of the compass where there has not been a sun crust forming on the surface. If you are in complex terrain it is important to make a plan to manage your sluff to avoid being pushed over a cliff or into an area you would rather avoid.

Natural avalanche in Skookum Valley which connected across this entire slope that likely released during or soon after the storm on Tuesday night. Photo Graham Predeger 3.8.24

Avalanche Problem 2
  • Wet Loose
    Wet Loose
  • Aspect/Elevation
  • 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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

Weather models have been struggling to accurately predict cloud cover the last few days. We are right on the edge of a low pressure system centered in the Gulf of Alaska, so a small shift in the location of that storm system could bring either full cloud cover or mostly sunny skies. Wet loose avalanches and cornice fall are likely if the sun comes out today. These will be most likely during the afternoon once the sun has had some time to warm up the snow surface. Cooler temperatures and cloud cover today might keep the sun at bay, but if the sun comes out keep an eye out for steep southern slopes and corniced ridges getting direct sunlight.

Wet loose avalanches releasing off rocky outcrops in the afternoon yesterday in Skookum Valley. Photo Graham Predeger 3.8.24

Weather
Sat, March 9th, 2024

Yesterday: Mostly sunny skies and light winds averaging 0-5 mph with gusts up to 15 mph from variable directions. Temperatures stayed cool yesterday, in the low 20s F at lower elevations and teens F at upper elevations.

Today: Mostly cloud skies are expected today, however weather models have been struggling to accurately predict cloud cover the last few days. We are right on the edge of a low pressure system centered in the Gulf of Alaska, so a small shift in the location of that storm system could bring either full cloud cover or partly sunny skies. Light winds averaging 0-10 mph from variable directions are expected today, with a shift towards easterly winds overnight averaging 5-15 mph with gusts to 30 mph. Snow showers are expected to start this evening around 8pm, with up to an inch of new snow falling overnight. Temperatures look to remain in the mid 20s F at lower elevations today and teens F at upper elevations, which will bring snowfall down to sea level overnight.

Tomorrow: Light snowfall is expected to continue throughout the day on Sunday, with 1-4″ of new snow falling down to sea level. Winds will remain out of the east with averages of 10-20 mph and gusts up to 35 mph. Temperatures are expected to stay in the mid to upper 20s F at lower elevations and low 20s F at upper elevations.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 19 0 0 90
Summit Lake (1400′) 17 0 0 45
Alyeska Mid (1700′) 22 0 0 93
Bear Valley – Portage (132′) 21 0 0
Grouse Ck (700′) 25 0 0 64

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16 W 5 13
Seattle Ridge (2400′) 18 N 2 9
Observations
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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.