Chugach State Park

Archives
Issued
Fri, February 16th, 2024 - 7:00AM
Expires
Sat, February 17th, 2024 - 7:00AM
Forecaster
CNFAIC Staff
Conditions Summary

Weekend Avalanche Outlook

Saturday, February 17th – Sunday, February 18th

Bottom Line: After a week of very strong winds and a few notable natural avalanches, triggering a wind slab avalanche remains a concern going into the weekend. Additionally due to the wind affected snow overlying a buffet of persistent weak layers, the potential to find the wrong spot and trigger a deeper avalanche should also be a consideration. Steep, wind-loaded slopes will be the most suspect. Look for signs of instability and evaluate snow and terrain carefully.

Special Announcements

Summit Lake Avalanche Accident:  A group of three backcountry skiers on John Mtn triggered an avalanche on Tuesday afternoon. Two of the three people involved sustained injuries, and the third did not survive. Our deepest condolences go out to the friends and family of the deceased. We have posted a preliminary accident report here and will publish a full report by the end of next week.

 

Recent Avalanches

Recent Avalanches: Over the past week, we have had four observations in the Chugach State Park with seven documented natural avalanches—primarily in the South Fork of Eagle River between February 12th and February 14th, with one reported avalanche in Bear Valley (above Nickleen Drive). One of the avalanches hit the Hiland Road.  The start zones of all the avalanches ranged between 3,300′ to 3,700′ on W, NW, and NE aspects. From the observations, it looked like the avalanches were all wind triggered slab avalanches that we suspect broke on a weak layer within the snow. However, seeing the avalanche crown lines was difficult because the wind filled them back in so quickly. It is worth noting that a few of these avalanches were large enough to bury a person. To read more about the avalanches in the South Fork of Eagle River—check out this observation.

The forecasting team relies heavily on public observations, and we always appreciate any information you all have to share. It takes a community to make an avalanche center run. Thank you!

Weather Recap: This week’s theme has been high winds and warming temperatures. We had a significant wind event that started Monday morning and eased off a bit Wednesday afternoon. Upper elevations have stayed breezy for the remainder of the week. The southeasterly event and pattern for the week brought sustained 25 to 50 mph winds with gusts up to 85 mph. Temperatures ranged from 15 F to 49 F with an average of around 30 F, a warmup from the temperatures we have seen over the last couple of weeks. A trace to an inch of snow fell last weekend in the Outlook area.

Snow depth remains variable across the range. Moving forward, it is the time of year to start tracking surface conditions on southerly slopes as warm temperatures and solar radiation may start to form melt-freeze crusts.

Weather Forecast: Skies should stay clear overnight tonight with lows in the mid-20s F. Southeast winds today were blowing 10 to 15 mph with gusts into the 20s and are forecast to continue until Saturday evening, becoming light overnight through Sunday. Clouds are expected to move in Saturday and increase, becoming overcast with a chance of snow Sunday into Monday. The unsettled weather pattern looks to continue into the week, with light snow and the potential for rain. Temperatures will be in the mid-20s to mid-30s F.

The natural avalanche that buried Hiland Road on 2.12.24. Photo: Peter Wadsworth 2.13.24

Natural avalanche in South Fork of Eagle River between Solstice Gully and Swiss Bowl. Photo: Peter Wadsworth 2.13.24

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
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.
More info at Avalanche.org

Staying on brand for the Front Range, the winds over the past week are the main story going into the weekend. In addition to triggering a few natural avalanches, the southeasterly winds were strong enough to scour into old wind-affected snow and redistribute it onto leeward slopes. The wind effect is clearly obvious when looking around the mountains. If venturing out to give the wind blasted surface conditions a try, triggering wind slab in steep, loaded terrain may be possible. Pay attention to any hollow-sounding snow (indicating weak or softer snow below), look for shooting cracks and remember you could be well out onto a slope before it fails. This much wind effect often makes slabs very stubborn to trigger but could catch you off guard if they happen to release. A wind slab avalanche could also step down and fail on one of the buried weak layers in the snowpack resulting in an larger avalanche (see Problem 2).

Wind scoured ridges and wind-loaded features in Two Bowls. Photo: Peter Wadsworth 2.13.24

Avalanche Problem 2
  • 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

Not to sound like a broken record but… We are still worried about a few different persistent weak layers buried in the snowpack. The larger avalanches that were triggered by the winds this week were deep enough to have likely failed on one of the layers of buried near-surface facets we have been talking about for weeks. An observer this week in the South Fork of Eagle River reported experiencing two larger collapses (whumpfs) while skinning, which is also usually attributed to weak snow falling below a slab. This prompted the observer to turn tail and ski back to the car. There is also a weak layer of snow at the base of the snowpack that has been observed in some higher elevation snow pits. Persistent slab avalanches are often triggered from thin spots in the snowpack where the weight of a person can impact the weak layer and cause a failure. It’s not always the first person on the slope with a set-up like this that triggers the avalanche—it could be the fifth or tenth.  Triggering an avalanche that fails on one of these buried weak layers remains a concern and should be part of the terrain choice decision-making this weekend.

Hunter Pass snow pit. 2.12.24

Observations
Recent Observations for Chugach State Park
Date Region Location
05/29/24 Chugach State Park Avalanche: Harp mtn west aspect
05/07/24 Chugach State Park Observation: Mt. Eklutna
04/27/24 Chugach State Park Avalanche: Chugach Front Range Powerline Valley
04/16/24 Chugach State Park Observation: South Fork of Eagle River
04/13/24 Chugach State Park Avalanche: South Fork Hiland Road
04/10/24 Chugach State Park Observation: Chugach Front Range Flattop
04/09/24 Chugach State Park Observation: South Fork of Eagle River
04/08/24 Chugach State Park Avalanche: Arctic Valley/ Gordon Lyon
04/06/24 Chugach State Park Observation: Eagle River South Fork
04/06/24 Chugach State Park Avalanche: False Peak

This is a general backcountry conditions summary. This advisory does not apply to highways, railroads or operating ski areas.