Seward & Southern Kenai Mtns

Archives
Issued
Fri, December 29th, 2023 - 7:00AM
Expires
Sat, December 30th, 2023 - 7:00AM
Forecaster
Daniel Krueger
Conditions Summary

Weekend Avalanche Outlook

Saturday, Dec. 30 – Sunday, Dec. 31

 

Bottom Line: With winds picking Friday night and on Saturday evening, and possibly receiving up to 5” of new snow starting Saturday evening, wind slabs are our main concern for the weekend. These will be more likely and more sensitive at higher elevations, up to 1-2’ deep, and large enough to bury a person. 

 

Recent Avalanches

Recent Avalanches: Over the past week we’ve observed avalanches throughout the Seward zone, including a natural avalanche cycle after the holiday storm where an avalanche crossed the highway near the Sterling Wye. The storm cycle was followed by multiple natural wind slab avalanches later in the week. We saw old wind slabs near Lost Lake yesterday as well as avalanches that likely occurred from last weekend’s storm. Glide cracks and glide avalanches have also been identified throughout the advisory area. 

 Weather Recap: In the past week Seward has received roughly 15” of snow equaling 2.6” snow water equivalent (SWE) accompanied by strong ridgetop winds. The holiday storm came in warm, bringing rain to 1500’. Winds decreased, skies cleared, and temperatures dropped to single digits on Tuesday (12/26). Temperatures the rest of the week averaged between 5 F and 20 F. 

Weather Forecast: Northerly winds on Friday will increase to 20 mph overnight before decreasing during the day Saturday. We are anticipating a brief storm to reach the peninsula late Saturday afternoon into Sunday. Clouds will begin to move in Saturday afternoon accompanied with east winds averaging 10-15 gusting to 20 mph and up to 5” snow. Below 300’ may receive rain or a rain snow mix. Temperatures will be near 0 F rising to the low 30’s F by Sunday evening.  

 

Avalanches observed after the 12/22-12/23 Holiday Storm. Photo by Sam Mclain 12.26.2023 

 

 

 

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

Our primary concern is another round of reactive wind slabs forming over the weekend. We are expecting strong northerly winds Friday night, switching southerly by Sunday morning along with a few inches of new snow. Wind slabs 1-2’ deep may be found on multiple aspects with wind changing direction in the middle of the weekend. Wind slabs tend to form below ridgelines, across gully features and below rollovers and are most reactive during and immediately following wind events. Watch for red flags such as blowing snow, recent avalanches, cracks that shoot out from your machine, board, or skis and whumpfing sounds. These clues can give you a clear sign that conditions are dangerous, but keep in mind that you won’t always see all of these red flags even if the snowpack is capable of producing an avalanche.

Yesterday, surface hoar was observed in a few isolated areas on Lost Lake. If this layer gets buried it might make wind slabs more reactive in isolated slopes and it will be important to assess. We have more info in our observation from Lost Lake you can read here.

Wind Slab releasing below the ridge of a wind loaded hill. 12.28.2023

 

 

Wind on ridgetops and peaks transporting snow. 12.28.2023

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

Last weekend’s storm covered a layer of surface hoar that had developed across the region. We have not seen or heard of any avalanches failing on this layer in the Seward zone, and based on the limited info we have, it does not seem to be a major concern in large parts of the Seward area. However, with limited information in the region, especially Snug Harbor, it is possible that this weak layer exists on some slopes and is capable of creating an avalanche that could bury a person or machine. These layers can be tricky to identify. If you are touring or snowmachining, it is a good idea to travel a bit more cautiously than normal until you are confident in your snowpack assessment. If you feel like sharing your findings, take some pictures and help us out by submitting observations!

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

After the Holiday storm, glide avalanches were observed near Kenai Lake. Although we have not seen evidence of widespread glide avalanche activity in the Seward area, it is worth mentioning because it has been a concern in other forecast regions. Because these avalanches release to the ground, glide cracks can be easy to spot as “brown frowns” as they open or “brown spots” when they release. It is important to minimize exposure under these glide cracks because they can spontaneously release and be large and dangerous. 

Weather
Fri, December 29th, 2023
Fri, December 29th, 2023
Weather Forecast Links:

NWS Point Forecast: Point forecast near Lost Lake.

NWS Avalanche Weather Guidance (AVG) forecast page: Zoom into the Anchorage bowl for special detailed winter forecast.

Windy.com Spot Forecast: Spot forecast for Lost Lake. (tip: scroll through models using the links at the bottom of the page, and change locations by clicking on the map).

Weather Stations

Grouse Creek Divide Snotel

Lost Lake Weather Station

Observations
Recent Observations for Seward & Southern Kenai Mtns
Date Region Location
04/16/24 Seward Observation: Lost Lake
04/10/24 Seward Observation: Lost Lake
04/03/24 Seward Observation: Snug Harbor
03/31/24 Seward Avalanche: Lost Lake
03/27/24 Seward Avalanche: Tiehacker Mountain
03/14/24 Seward Observation: Lost Lake via Snug Harbor
03/06/24 Seward Observation: Carter Lake
03/03/24 Seward Observation: Victor Creek, 1k – 1.6k elevation
02/29/24 Seward Observation: Carter Lake
02/26/24 Seward Avalanche: Mt Marathon
Riding Areas

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