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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, February 28th, 2022 - 7:00AM
Expires
Tue, March 1st, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at elevations above 2,500′ on all aspects. Lingering wind slabs formed by the strong winds last Friday may still be triggered by people on steep slopes. These could be up to 2-3′ in depth and be quite hard, allowing a person onto the slab before it releases. Additionally, triggering a cornice fall while on ridgelines is also possible. On slopes below 2,500′ triggering an avalanche is unlikely and the danger is LOW.

SUMMIT LAKE:  A thinner and weaker snowpack exists south of Turnagain Pass in the Summit Lake area. Triggering a wind slab that steps down to a deeper weak layer could be possible. Extra caution is advised in these shallow areas on the Kenai.

Mon, February 28th, 2022
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
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

No avalanches were seen or reported from yesterday.

Avalanche Problem 1
  • 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

Another quiet weather day is on tap with some high clouds moving overhead and only light and variable winds. The main avalanche concern will continue to be lingering wind slabs at the upper elevations. These are quite hard and anywhere from a few inches to a few feet thick. They formed three days ago during Friday’s storm. At this point, these slabs should be fairly stubborn to trigger; we could not get any to crack out on us yesterday. That said, on steep wind loaded upper elevations slopes someone might still be able to get one of these to move. Even a smaller wind slab in exposed, steep, and rocky terrain could have high consequences. Watch for any cracking in the snow around you or collapsing/whumpfing under you.

Cornices:  These have grown to a healthy size this season, especially after Friday’s 100mph winds… As usual, be sure to exercise extra caution and give them a wide berth.

Sluffs (loose snow avalanches):  Watch for dry sluffs on steep slopes that harbor softer surface snow. Additionally, watch for wet or moist sluffs on sunny slopes that might warm enough this afternoon due to calm winds and potential for sunshine.

During yesterday’s mostly sunny skies, we were able to see more evidence of the natural avalanche cycle from Thursday night and Friday. Below are some photos from Turnagain Pass where widespread wind slab avalanches occurred. Some quite large and filling creek bottoms.

Wind slabs with wide propagation that released on Friday. This is on the west face of BBQ Hill on the backside of Seattle Ridge. Photo taken, 2.27.22.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • 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.
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 thin snowpack areas around the region there remains weak snow surrounding old buried crusts. As we’ve been mentioning, these areas are on the western side of Girdwood Valley in the the Crow Pass zone and on the south end of Turnagain Pass in the Silvertip area and especially further south outside of the forecast zone in Summit Lake. Triggering an avalanche in these old layers is trending to unlikely without a significant weather event, however in the Summit Lake area there is more uncertainty. If venturing into these thin snow covered areas, be extra cautious and consider the consequences in the case a larger avalanche was triggered.


Large natural slab avalanches in the Summit Lake area that occurred during Friday’s storm. This was seen from Summit Peak and is on Butch (the shoulder of the Incredibowls). Photo by Aleph Johnston-Bloom, 2.27.22.

 

Glide Cracks: These continue to slowly open in various areas around the region. We have not heard of any releasing for some time, but they can be very unpredictable and avoiding time under glide cracks is always recommended.

Glide crack that sits just to the south of the motorized up-track on Seattle Ridge. Photo taken by a rider yesterday, 2.27.22.

Weather
Mon, February 28th, 2022

Yesterday:  A surprise day of mostly sunny skies. Ridgetop winds were light and variable. No precipitation was recorded across the region. Temperatures were in the 20’sF at the mid and upper locations before cooling off to the teens overnight.

Today:  Another calm and pleasant day is on tap. Ridgetop winds should be generally light and variable trending southeast later in the day with no precipitation forecast. Temperatures look to warm into the mid 20’sF at the higher elevations and low 30’sF in the parking lots.

Tomorrow:  A small chance of snow flurries tonight with partly cloudy skies expected tomorrow. Ridgetop winds are expected to be light from an easterly direction. A chance for more active weather and precipitation may push in later this week.

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

Temp Ave (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 0 0 94
Summit Lake (1400′) 25 0 0 41
Alyeska Mid (1700′) 29 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21 W 4 11
Seattle Ridge (2400′) 25 NW 2 5
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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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