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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Aleph Johnston-Bloom  
Saturday, April 15th 2017
Created: Apr 14th 20:49 pm
Summary and Current Conditions

We are no longer issuing weekly Summit Lake snowpack summaries for 2016/17; 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 16th and then switching to 4 days a week until our final advisory on April 29th. 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. 

Surface hoar in December... A theme for the season. 

The aftermath of the the April Fool's Storm and avalanche cycle on Moose Mountain. Photo taken on 4.5.17


Primary Concern

The snowpack in Summit is shallow and there are multiple layers of weak snow. The recent avalanche cycle illustrated the potential avalanches that these weak layers can produce when overloaded. As the snowpack continues to transition from winter to spring keep this in mind. How are the layers of buried surface hoar, near surface facets and depth hoar going to react to change?

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 Fool's avalanche cycle on Fresno. Photo 4.14.17

Wet Slab Avalanches: Wet slab avalanches are currently 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 for this type of avalanche to occur.  This is the current sitiuation in the mid elevation on southerly slopes now (4.14.17). 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 slab and rain or sun sends water down into the snowpack. Weak layers and water in the snowpack are generally an unstable combination. 

Wet Slab Seattle Ridge, 4.14.17 (This was observed in motion at 1 pm)

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.  

Large slab on the north side of Tenderfoot that released during the April Fool's storm avalanche cycle.

 

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 on the Manitoba/Silvertip ridgeline

Glide Avalanches: Compared to last season this one has been very quiet in regard to glides. However, glides cracks are now opening and starting to release around Turnagain. Remember if you see them opening up in Summit they are unpredictable and can be quite dangerous! Avoid travel under glide cracks.

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???

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: Apr 11, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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