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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   CNFAIC Staff  
Friday, April 13th 2018
Created: Apr 13th 19:45 pm
Summary and Current Conditions

We are no longer issuing weekly Summit Lake snowpack summaries for 2017/18; however, this does not mean that the avalanche season has ended - see below for some SPRINGTIME TIPS to review.

Keep tabs on the Turnagain Pass advisory page as well as the Summit Lake area observations. We will be posting daily Turnagain advisories until April 15th and then switching to 4 days a week until our final advisory on April 28th. We will continue to post observations as long as you keep sending them in! Let us know what you are seeing this spring!

As always check the nearby weather stations before heading out around Summit Lake and the "Weather" link above for regional information.

Summit Lake Mile Post 45 for ridgetop winds and temperatures.

Summit Creek SNOTEL for temperatures and precipitation at road level.

We want to extend a huge THANK YOU to Alex McLain at the CNF Seward Ranger District for his weekly observations and contributions to the program in Summit Lake. We also really appreciate all the folks recreating in this area who have taken the time to send in observations. Your information is also integral to the being able to provide information in the region. 

"Like" the Friends of the Chugach National Forest Avalanche Information Center on Facebook and follow us @chugachavy on Instagram. We will continue to post throughout the summer. 

 

One of the most noteable avalanches from the season. This slab was triggered by a couple of skiers ascending a skin track. It was a hard slab (sastrugi in places) over a facet/crust combination. No one caught or carried.


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Primary Concern

The snow cover in the Summit Lake area is generally shallow (3-6' deep) and there are multiple weak layers within the snowpack. As the mountains continue to transition from a winter snowpack to a spring one, keep in mind the unpredictability of wet snow avalanches. These can release naturally when the crusts in the pack melt and lose strength - often during the heat of the day when the sun shines (the afternoon/evening) or during warm, cloudy and rainy weather. With weak snow near the ground inhibiting bonding, wet avalanches can take the whole snowpack with them and send thick wet debris into valley bottoms. This is nothing to mess with - keep a close eye out for this type of acitivity.

Wet loose avalanches that are gouging to the ground (April 11th, 2018) - a sign the entire snowpack is losing its strength. These types of avalanches can become much larger in bigger terrain.

 

Two well-documented weak layers in the middle and base of the pack can easily be found in pits.  They are dormant for the time being, but rapid loading or warming could wake them back up.

At elevations below 2000' the snowpack is extremely thin and has a very weak structure.  In this pit, weak facets at the ground would not even support compression test columns under their own weight, and propagated fractures with easy force.

 

SPRINGTIME AVALANCHE TIPS -  Timing and observations are crucial!  This transition time can have unique and sometimes hazardous snowpack characteristics. Ask yourself these questions: Am I dealing with winter snow (cold and dry) or spring/summer snow (wet, warm and/or refrozen)? Or is it some combination? What weather factors have affected to snowpack today and recently?

Remember the Red Flags that indicate instability!

Are there recent avalanches? What kind?

Cracking? Collapsing?

New snow? Rain?

Wind loading?

Rapid Warming? Did it freeze last night? How deep are you sinking in?

While many people may have written off winter and have transitioned to springtime activities, there is still plenty of snow in the mountains.  On any given day conditions can range from warm and sunny t-shirt weather, to pouring rain, to cold & snowy mid winter conditions.  Being able to recognize and respond to specific avalanche concerns is key in making effective decisions in avalanche terrain. 

Loose Snow Avalanches: Both dry and wet loose avalanches are common springtime avalanche concerns.  Pay close attention in steep terrain, especially when the sun first hits freshly fallen snow.  Remember loose avalanches can be particularly hazardous if they push you into a terrain trap. Wet loose avalanches can trigger wet slabs on the slopes below. 

Wet loose avalanches and old debris from April 10-11th on the West aspect of Twin Peaks.

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Wet Slab Avalanches: Wet slab avalanches are soon to be happening and they are often a possibility this time of year.  A combination of a slab, weak layer and water percolating into the weak layer is what is needed.  This is the current sitiuation in the mid elevation on southerly slopes in Turnagain pass on April 11th. Know that as temperatures rise this set-up will become possible in the higher elevations. It is also important to pay attention to if we get another storm that deposits a new layer of snow and rain or sun sends water down into the snowpack. Water running down into weak layers are generally an unstable combination. 

Wet Slab Seattle Ridge, 4.11.18 


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Storm Snow: It is still possible to get significant snowfall this time of year.  Pay attention to how much new snow has fallen and what surface it is sitting on.  Is there a foot of new snow sitting on a crust?  Even without a persistent weak layer between the slab and the bed surface, it is still possible to trigger dangerous slab avalanches.  These storms slab may also be tender and reactive right as they start to warm in the spring sun or with a rapid temperature rise.  

 

Wind slab: It is also important to continue to pay attention to wind direction and loading patterns. New snow can quickly be loaded on leeward slopes and form touchy wind slabs. Look for areas of pillowed snow and watch for cracking. Like storm snow, wind slabs can be tender with the first warmup after the loading event. 

Cornices: Many slopes have large cornices looming above them.  Knowing exactly what will tip the scales is difficult. To date we have yet to see a wide spread natural cornice fall cycle. Some factors that contribute to cornice fall are sun, heat, and new snow with wind.  Give cornices a wide berth and take measures to minimize your exposure beneath them. Remember they have a tendency to break much further back than expected.

Cornices above Butch Mtn on April 13, 2018


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Below are some ways to both anticipate and deal with the above mentioned avalanche concerns: 

    •    Watch for the "shed cycle" in the higher elevations. One great way is to keep an eye on the ridgetop weather stations (click HERE). Avalanche activity often follows multiple consecutive days (usually 3) of above freezing overnight temperatures.  Careful route planning to stay out from under slopes with wet and rotten snow is essential during this period. 

    •    Once the snow has undergone the transition to a summertime pack and is freezing at night and warming during the day (the corn season), hitting the slopes early and getting off them when they become too sloppy is critical.

    •    Damp or wet snow more than 6" deep is a sign that it's time to exit the area. Following the aspects as the sun heats up the slopes over the course of the day, East to South then West, can make for great riding/skiing days ending in sunny tailgating. North slopes may still have winter like conditions. 

    •    Keep in mind, cloud cover 'holds in the heat' and can dramatically limit overnight refreezing.  A shallow to no refreeze will not only give daytime heating a jump start on weakening the pack, but can produce less than stellar riding conditions.

    •    Beware of warm storms where rain is falling on snow, especially when rain is falling on cold dry snow. This can quickly increase the avalanche danger.


     •    Stay off of CORNICES.  When approaching from the side or above, make sure you can see where the cornice ends and the underlying terrain begins.  If you can’t see that transition area, move away from the edge.  If you find you and your group below cornices, expose only one person at a time and move efficiently through those areas. 

  •    Lastly, don't forget to plan your route back to the car. Does it take you under slopes that were frozen and safe earlier in the day, but now have been cooking in the sun waiting to slide on your return? Under cornices? Under glide cracks?

Are you sinking in???

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Thank you for reading and have a safe spring in the backcountry!   

 


This is a general backcountry avalanche advisory issued for Summit Lake Area as the core advisory area(this advisory does not apply to highways, railroads, or operating ski areas).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.

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USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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