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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   Heather Thamm  
Saturday, December 31st 2016
Created: Dec 30th 20:44 pm
Summary and Current Conditions

This week the Summit Lake zone in the Kenai Mountains received ~10” of new snow during two different storm events, one over Christmas weekend and the other on Dec.30th. The second event on Dec.30th was accompanied by very strong South and West winds, unusual wind directions, which produced a natural avalanche cycle throughout Summit Lake. Widespread natural avalanche activity was observed on North, West, and South aspects of many mountains between the Hope Wye and Tri-Tip. 

The snowpack prior to this event is best described as shallow and has been faceting-out over the last few weeks due to cold temperatures, clear skies and very little snowfall this season. In the lower elevations in the trees (below 2000’) there is only 12-15” of snow where a crust on the ground has completely faceted out and depth hoar has been found. In the upper elevations several crust/facet layers can be found near the ground sitting under 0-5 feet of total snow. This variability is due to strong winds distributing snow and creating very scoured ridges. Due to the unusual wind direction of the Dec.30th and shifting winds throughout the storm wind loading is possible on multiple aspects.

The weather over the next few days and into next week looks like clear skies and cooling temperatures. A cautious mindset and conservative decision making should be used in the coming days and week if headed to Summit Lake. Triggering an isolated wind slab or a larger more dangerous persistent slab will be possible. Be on the lookout for shooting cracks, whumpfing sounds or recent avalanche activity, these are all signs to stay off of steep avalanche terrain.

Since this report is a weekly summary, PLEASE be sure to follow the Turnagain Pass advisory for current weather and avalanche conditions. Please help us keep tabs on the Summit area and if you see any avalanche activity send us an observation HERE. Thank you to everyone who has already submitted observations this season - you can see those HERE!

Natural avalanche observed on the NW face of Moose Mountain in Summit Lake. Photo taken at 12:20pm on Dec.30th

 


Primary Concern

Due to cold temperatures and clear skies over the last month widespread faceting has occurred within the snowpack in Summit Lake. In the lower elevations depth hoar has been found on the ground and in the upper elevation several layers of facets are lingering under wind stiffened snow. There is also a layer of surface hoar that was buried on Dec.24th that may be preserved in certain areas. There is much uncertainty about the snowpack following the Dec.30th storm and how the snowpack will adjust following such an extreme wind event. Persistent weak layers like facets take a long time to heal before they go away, thus this problem is likely to linger for awhile. Expect many ridges to be scoured and snow surfaces to be hard and supportable. Wind loaded slopes will be suspect and triggering a slab will be more likely in thinner areas of the snowpack near rocks or where the snow transitions from a ridge to a steeper slope.

Natural avalanches on a West aspect of Lonestar (foreground) and Southern aspects of Twin Peaks (background) due to very high winds on Dec.30 

 

Correction- this snow pit was dug at 2400', not 2200' as stated in the diagram. This represents the mid and lower elevations in summit lake before the Dec.30th wind event. Expect many of the facet layers to still be intact and preserved.

This pit was from last week before the Christmas storm in the upper elevations of Tenderfoot. 

 

 

 


Secondary Concern

Wind slabs will be most suspect where the snow is supportable, hollow feeling and more loaded.  Due to the unusual wind directions from the Dec.30th storm, wind slabs are possible on a variety of aspects and elevations. Don’t be caught off guard in the wrong place. Wind slabs are notorious for breaking above you in places with little snow where taking a ride is undesirable. It is also possible that a small wind slab could step down into a deeper layer of the snowpack and produce a much more dangerous avalanche as described above.

Wind loading on the NW aspect of Moose Mnt. just prior to the avalanche that released in the above picture. 

 

Cornices could also be tender and easy to trigger following this recent wind event. Give cornices a lot of space and avoid being directly under them. They are very unpredictable. 

 


Mountain Weather

Last weekend during the Christmas storm (12/24-12/26) Summit area recieved about 4-6” of snow and moderate NE winds, much less snow accumulation than Turnagain Pass which had 2.5 feet over the same period. Throughout the week temperatures averaged in the low 20F’s. On 12/30 another storm moved through our region leaving an additional 4” of snow followed by strong ridgetop winds averaging in the 40’s (mph) and gusting in the 60’s. This wind data is based on observations and regional wind patterns. The Summit Lake MP 45 weather station is in a sheltered area and did not record representative data from this event. The Fresno Weather Station is also currently down.

Tomorrow (Saturday) clear skies and cooler temperatures (teens F) are expected and winds are expected to decrease by morning. No precipitation is in the forecast for the next few days, and a high pressure is predicted to move into our region, keeping temperatures cool and skies clear into early next week. 

Visit the CNFAIC weather page for a current forecast and up to date weather station data for the Summit Lake area!

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: Jan 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenAccess is thru the gate on the right side of the parking lot as you drive toward the outhouse. Please park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlease cross Railroad tracks at 90 degrees to the rails and clear the corridor. It is Illegal to ride up and down Railroad tracks. Tracks are currently active. Please observe and stay off PRIVATE PROPERTY adjacent to the Portage Valley.
Skookum Drainage: Open
Turnagain Pass: Open
Twentymile: OpenPark at Portage rail depot. Cross tracks and follow marked corridor (Bamboo poles) approx. 3 miles up Valley to open riding areas.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenOpen to motorized use 1/15. Please STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenOpen to motorized use 1/15. Please 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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