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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Aleph Johnston-Bloom  
Friday, February 3rd 2017
Created: Feb 3rd 19:38 pm
Summary and Current Conditions

Once the skies cleared enough on Sunday a fairly widespread avalanche cycle from the January 26/27 storm was observed. The poor snowpack structure that has been discussed over the past few weeks was overloaded by storm snow and wind. There have not been any reports of human triggered avalanches in the Summit Area this week. However, there were two on Turnagain Pass yesterday, including one in Lynx Creek which is close to Summit Lake. Sunshine and warm temperatures this weekend are going be a big draw for those looking to get out in the mountains. If venturing out in the Summit Lake area it will be important to remember poor snowpack structure and propagation potential still exist (see Primary Concern below). The current snowpack warrants elevated caution. In snowpack tests it is some of the most reactive we have seen recently which indicates lingering instability. Watch for changing conditions. If the area does receive new snow or strong winds the hazard will rise. 

During the week, stay tuned on the most current up to date avalanche and weather conditions on the Turnagain Pass daily advisory and the Summit Lake Observations Page!. Also, Please help us keep tabs on the Summit area - if you see any avalanche activity send us an observation HERE

  • The final CNFAIC report on the snowmachine avalanche fatality in the Snug Harbor area on Saturday, January 28th is available HERE.  We want to thank those involved for their willingness to share their experience for others to learn from. Our thoughts continue to be with the victim's family, friends and rescuers.
  • The Southern Kenai Mountains, including Seward, Snug Harbor and Lost Lake zones continue to have dangerous avalanche conditions. This region received another 1-2' of wet heavy snow early in the week and large propagating deep slab avalanches (5+' thick) are possible on slopes over 35 degrees. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.

 

Large natural avalanches from the 26/27 storm.

A closer look at one of the crowns from 26/27 cycle.


Primary Concern

Overall the snowpack in Summit Lake is still shallow which has been noted all season long. The January 26/27 storm built a more substantial slab that is now resting on weak basal facets (sugar snow). This snowpack set-up is pretty easy to feel. In protected area and lower elevation pole tests drop to ground and stepping out of your skis results in full leg penetration. On wind effected slopes the slab is stiffer and more supportable but still rests on very weak snow. Slopes that haven't slid will continue to be suspect. Snowpack tests show that this set-up still has the potential to be triggered and fracture across a slope. It is notably more consistently reactive than the Turnagain Pass snowpack. Last weekend an observer noted whumpfing, cracking and collapsing while traveling. These signs might not be present anymore but this doesn't mean an avalanche won't be possible. These avalanche could be large and dangerous. The entire snowpack may run to the ground. Persistent slab avalanches are often triggered in thinner spots. It will be important to carefully choose terrain, only exposed one person at a time, group up in safe zones, have an escape route planned and watch your partners. 

 

 

 


Secondary Concern

In addition to persistent slab avalanches there are a few other avalanche concerns to pay attention to this week. All of these concerns could be a hazard separately or once initiated, trigger a larger persistent slab deeper in the snowpack. Warm temperatures and direct sunlight may also play a factor in all of these concerns. We have reached the time of year. The sun is out and affecting the snow in terrain on the Southern half of the compass. A small crust was observed forming on Thursday on steep southerly slopes. 

Wind Slabs: Old stubborn wind slabs may be triggered on leeward slopes. Looked for pillowed or drifted snow, listened for hollow sounds and avoid areas with stiff snow over soft snow. Warming temperatures and direct sunlight may make these slabs easier to trigger.

Loose snow: With 4-8" of loose snow on the surface over a dense base, watch your sluffs and watch how the sun is affecting the snow around you. 

Cornices: Give cornices wide berth, avoid travel on slopes below them and remember they can break farther back onto the ridge than expected.  If cornices do break and fall they could trigger an avalanche on the slope below. 

 

Newly formed surface hoar is widespread. This will be important to keep track of and remember the next time the area receives snow. 

 

 

 


Mountain Weather

After the 26/27 storm Summit Lake received another inch of snow Saturday (28th) and then another couple inches Monday into Tuesday with a small system moving through the area. Winds were a stronger over those two days gusting into the 30s from the East. Winds shifted to the north and west and became light during the week. Skies cleared on Wednesday bringing warm temperatures to the area, rising into the 40s in the Alpine. An inversion kept cooler temperatures in valley bottoms. The pattern looks to be very similar into at least the middle of next week with warm temperatures, sunshine and light winds. Later in the week there is chance for snow and cooler temperatures. Keep tabs on the weather on the Turnagain Pass advisory page. 

The best way to see if it's snowing at Summit Lake is to look at the RWIS webcam snow stake HERE and the NRCS snotel site HERE. The above MP 45 station is the best ridge top wind and temperature information. Fresno Weather Station will not be operational for the rest of the season. 

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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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