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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, April 26th, 2022 - 7:00AM
Expires
Wed, April 27th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains CONSIDERABLE for naturally occurring large wet springtime avalanches. These can be wet loose, wet slab or glide avalanches. They can be very dangerous and are releasing in high-use areas. Additionally, triggering a lingering slab avalanche 1-3′ thick on upper elevation northerly facing slopes is still possible. Cornice falls will also be possible to trigger; give these a very wide berth along ridgelines.

Avalanche danger exists near sea level as well. Debris from an avalanche occurring above could run into these lower elevations. Avoid being at the bottom of large avalanche paths, such as the Bryon Glacier Trail in Portage Valley.

WEDNESDAY AVALANCHE OUTLOOK:  Avalanche conditions will remain dangerous for Wednesday. The springtime avalanche cycle is occurring and large wet avalanches are expected to continue to release. The next forecast will be Thursday, April 28, at 7am.

Special Announcements
  • End of Season Operations:  This is our final week of forecasting. There will be a forecast this Thursday and Saturday with our springtime tips posted on Sunday, May 1st.
Tue, April 26th, 2022
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
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.
Recent Avalanches

Seattle Ridge – Repeat Offender:  Around 5pm on Sunday, April 24th, there was a very large natural glide avalanche that released on the Repeat Offender slide path. The avalanche propagated large portions of wet slab on the descent and sent significant amounts of debris over the common motorized up-track. Four riders were descending the up-track when the avalanche occurred behind them. Two were able to outrun the debris and two were caught. One rider was mostly buried with an arm and back of helmet exposed. The other was not buried. The group was able to quickly assist the buried rider and all involved are OK.

Around 2.5 hours later (between 7-8pm) another smaller glide avalanche and wet slab released to the looker’s right of the original avalanche that sent debris over more of the up-track.

*We are currently compiling a report with additional details. Thank you to those that have passed along their information, photos and videos.

View from the toe of the avalanche the day after, 4.25.22.

 

Closer up view of the second release that covered more of the up-track. 4.25.22.

 

Looking down from the up-track. Photo by Hunter McConnel 4.25.22.

Avalanche Problem 1
  • Spring Conditions
    Spring Conditions
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Spring Conditions
Warmth has a tricky effect on snow. On the one hand it speeds up the stabilization of the snowpack (reduces the chance of slab avalanches). But a SUDDEN rise of temperature increases the chance of slab avalanches considerably. When this warm period is followed by cooling down, then the chance of slab avalanches reduces. Even more so: the more often the temperature changes, the more stable the snowpack becomes when looking at slab avalanches. Once the temperature becomes too warm we have to deal with wet snow avalanches.
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

Dangerous springtime avalanches are the main concern now and will be for the next week and even several weeks. Since the warm storm last Friday we have seen many large wet slab and glide avalanches release. A few clouds overnight kept some heat in and last night was the warmest night yet in the high elevations. This will only accelerate the melting of surface crusts and destabilizing of the snowpack today.

How we manage these springtime wet and glide avalanches is to simply not be in their way. They are predominantly occurring in the afternoon/evenings and on east, south and westerly aspects. Thinner snowpacks, with rocks/etc poking through, are also more suspect to avalanche. If you see recent avalanches on similar slopes/aspects, you can bet that more are on the way. Seattle Ridge is a great example of this for anyone that has been to Turnagain Pass in the last week.

It is good to note that even though wet avalanches and glide avalanches are technically different – they are occurring in sync right now. The one exception is that glide avalanches can release at anytime of day – even in the morning when the snowpack is more frozen. Watching for glide cracks and avoiding being under them is prudent in the morning as well as later in the day when things heat up.

Two different wet slab avalanches with debris running together on Seattle Ridge – across from the parking lot. Unknown exact time of release, but in the past few days. Photo taken 4.25.22.


Cornices:  With the very warm temperatures, these beasts are slowly oozing over and could start falling off at anytime. They also may be so close to failure it would not take much for people along ridgelines to get them to break. They also could trigger an avalanche below, threatening anyone that could be in the path. Just one more issue right now with the springtime thaw.

 

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

In the higher terrain on shaded slopes, watch for lingering slabs formed by last Friday’s 1-2′ of snow. These could be wind slabs or storm slabs and may still be able to be triggered by folks seeking out the drier snow. Watch for the telltale signs of visibly wind loaded areas, hollow feeling snow, cracking in the snow, and whumpfing. There were reports of whumpfing in the Pastoral area two days ago.

Weather
Tue, April 26th, 2022

Yesterday:  Mostly sunny skies were over the region with light NW winds along ridgelines. Temperatures reached 50F at sea level and the mid 30’sF along ridgetops.

Today:  A mix of sunshine and mid level clouds are forecast today with light northerly winds. A rain drop may fall here and there but no measurable precipitation is expected. Temperatures have fallen overnight into the 30’sF at the mid and lower elevations and should climb again into the 40’sF. Ridgetop temperatures are near 30F this morning and could climb into the mid 30’sF this afternoon.

Tomorrow:  Sunny skies are expected for tomorrow, Wednesday. Ridgetop winds are forecast to be light and variable. Temperatures could climb higher tomorrow at all elevations with the clear skies (low 50’sF at sea level and close to 40F along ridgelines). Sunny skies and warm temperatures look to remain through Friday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40 0 0 103
Summit Lake (1400′) 38 0 0 31
Alyeska Mid (1700′) 40 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 31 NW 3 8
Seattle Ridge (2400′) 34 N 2 5
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.
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