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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, April 8th, 2024 - 7:00AM
Expires
Tue, April 9th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger will start out LOW and rise to MODERATE as snow surfaces heat up through the day. Wet loose avalanches will be the main concern, starting with steep south-facing slopes. Be on the lookout for roller balls as an earlier indicator of increasing danger, and avoid traveling on or under steep slopes as temperatures rise this afternoon.

SUMMIT/SEWARD: Northwesterly winds are expected to be a bit stronger in our southern zones, making wind slab avalanches possible especially at upper elevations.

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Mon, April 8th, 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
Tue, April 9th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Tue, April 9th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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

Skiers observed multiple natural wet loose avalanches on the front side of Seattle Ridge yesterday afternoon. They also reported small sluffs in steeper north-facing terrain off Tincan Ridge.

Debris from natural loose avalanches on the front side of Seattle Ridge. Photo: Andy Moderow, 04.07.2024

Debris from skier-triggered sluff in Todd’s Run on the north side of Tincan Ridge. Photo: Andy Moderow, 04.07.2024

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

With another day of mostly sunny skies and mild temperatures on the way, wet loose avalanches will be the main avalanche concern. We had a clear night with cool temperatures so solar aspects and low-elevation terrain going through the melt/freeze cycle should have gotten a solid refreeze last night. The chances of triggering an avalanche will be low until those crusts soften in the middle of the day. Watch for rollerballs and pinwheels releasing on steep southerly slopes as an early indicator of increasing danger, and expect deteriorating conditions as the snow warms this afternoon. Be sure to plan on limiting exposure to steep overhead terrain later in the day since avalanches will likely release naturally.

Wind Slabs: While we do not expect it to be a widespread problem within our Turnagain Pass advisory area, you may encounter lingering wind slabs on isolated upper-elevation slopes. The most likely places to find a reactive wind slab will be in steep alpine terrain just below ridgelines or convex rolls. As always, you can reduce the consequences of triggering an outlier avalanche like this by traveling one at a time in steep terrain and watching your partners from safe spots outside of avalanche runout zones.

Rollerballs on a steep southwesterly slope. If you start noticing these moving this afternoon it is time to move into shaded terrain. 04.07.2024

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

We are still monitoring the interface from last weekend’s storm, which produced several very large avalanches right after the snow stopped falling. Everything we have been observing suggests this layer is healing, and we do not expect to see avalanches failing on this layer. That said, it is still something worth keeping in mind before committing to big, exposed terrain. The layer is around 1-2′ deep on average, and was most problematic on slopes on the south half of the compass where the storm fell on a stout crust.

Weather
Mon, April 8th, 2024

Yesterday: Skies started out mostly cloudy, but clouds cleared mid-morning with mostly sunny skies for the rest of the day. Winds were light out of the east in the morning, switching westerly with average speeds around 5 to 10 mph and gusts of 10 to 15 mph. High temperatures were in the low to mid 20s F at ridgetops and high 30s to low 40s at lower elevations. No precipitation was recorded.

Today: We’re expecting one more day of quiet weather before snow returns tomorrow. Skies should be mostly sunny with light northwesterly winds around 5-10 mph. Temperatures are expected to reach the mid 20s to mid 30s F during the day, then cool to the upper teens to low 20s F tonight. No precipitation is expected today, but the chances for snow will pick up overnight and into tomorrow morning.

Tomorrow: We will likely see a few inches of snow starting early tomorrow morning, with 4-8” possible in Girdwood and Turnagain Pass, and slightly more in areas closer to the coast. This system should bring snow to sea level. Easterly winds are expected to increase starting tonight, averaging 15 to 25 mph with gusts up to 30 to 35 mph. High temperatures are expected to be in the mid 20s to low 30s F with lows in the mid teens to low 20s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 0 0 97
Summit Lake (1400′) 27 0 0 45
Alyeska Mid (1700′) 31 0 0 111
Bear Valley – Portage (132′) 34 0 0
Grouse Ck (700′) 33 0 0 72

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 NE-W 6 17
Seattle Ridge (2400′) 24 E-W 3 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.