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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   CNFAIC Staff  
Saturday, March 25th 2017
Created: Mar 24th 11:17 am
Summary and Current Conditions

Finally a tiny break in the near month long stretch of clear sunny weather. By the end of last weekend Summit Lake received 1-2" of new snow. While not the significant dump we may have been hoping for, it is definitely a welcome change. Winds in the alpine have moved the snow around, but left the drifted snow soft. The new snowfall did lead to some new dry loose avalanching on steep slopes as well as a possible snowboarder triggered small wind slab on Tri Tip, South aspect. The snowpack in the Summit Lake area continues to have very poor structure with many persistent weak layers and highly variable depths ranging from 1-6'.

Expect to see continued clear skies and temps into the mid/high teens during the daytime through the weekend. There is still a high degree of uncertainty about what this next week will bring. If you are planning to get out in the Summit Lake area it will be important to keep a close eye on the weather since this will play a key role in determining snowpack stability. While the snowpack has begun to stabilize, it is still riddled with persistent weak layers and overall poor structure. Weather events such as a rapid warm-up, new snowfall, or rain could lead to widespread avalanching. Because the base of the snowpack in Summit lake is consistently rotten additional stress to the snowpack could result in avalanches propagating far across slopes and releasing down to the ground resulting in slabs ranging from 2-4' in thickness.

*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

Natural loose dry avalanches on steep slopes on Incredibowls

 

Ridgetops still bare from repeated wind events throughout the season


Primary Concern

The snowpack in Summit has been plagued by persistent weak layers this season. The cycles of snow, fluctuating temperatures, and high winds have left cohesive slabs sitting above weak faceted snow throughout the snowpack. In addition to the weak layers within the snowpack, small (2-3mm) surface hoar has begun to grow at all elevations, and sun crusts with near surface facets are forming on southerly aspects. These layers will be important to keep in mind if they are buried by snow in the coming week. As has been the case with most of this season remember that in most areas the base of the snowpack is still ~30cm of advanced facets over rotten depth hoar.

We may have not seen any recent avalanching on these persistent weak layers, but a rapid addition of stress to the snowpack could easily reactivate these weak layers. Added stress from rapid warming to above freezing temperatures, new snowfall, or rain can easily overburden these layers and lead to a widespread avalanche cycle. Be sure to keep your eyes open for any red flags such as  whumphing, shooting cracks, recent avalanches, and now that spring is here - wet or saturated snow. These are all indicators that the snowpack is overstressed and there is an increasing likelyhood of triggering an avalanche.  

Alternating layers of old wind slab over persistent weak layers

 

Additional avalanche concerns:

Loose Snow Avalanches:

The addition of 1-2" of new snow has resulted in recent dry loose avalanches on steep slopes. Expect human triggered sluffs if you plan to get onto steeper slopes. As solar radiation gets stronger and ambient temperatures increase remember to keep an eye out for signs of warming snow as they could be an indicator that conditions are warm enough to produce wet loose avalanches.

Dry loose avalanches from the recent storm snow

Cornices:

High wind events throughout the season have left large cornices along many ridgelines. If temperatures do rise above freezing there is an increased likelihood that cornices will break off. Cornices should always be given an extra wide berth if travelling along a ridge and minimize your exposure time spent under these backcountry bombs. 


Mountain Weather

This past weekend finally brought some snow to the Summit Lake area with snowfall totaling 1-2" by Monday morning. In the alpine this snowfall was coupled with light winds just strong enough to transport the new snow, but not strong enough to form new wind slabs. As the storm cleared off conditions returned to calm and clear with temperatures in the single digits in the mornings rising to the mid-teens during the day. The suns warmth is being felt during the day meaning conditions feel much warmer in direct sunlight. 

This weekend is expected to continue the trend of calm and clear with temperatures in the single digits at night rising to mid/upper teens during the day. As the weekend draws to a close there is still a lot of uncertainty about the type of weather the week will bring. There is potential for significant warming coupled with precipitation later in the week. It will be important to keep an eye on the weather since this will have significant impact on snowpack stability.

For the most current weather information visit the CNFAIC weather page HERE.

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: Mar 25, 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: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
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
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