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Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   CNFAIC Staff  
Saturday, February 3rd 2018
Created: Feb 2nd 12:33 pm
Summary and Current Conditions

During the past week, the Summit Lake region on the Kenai has been dominated by dry, cold and sunny weather.  The last snowfall was early on January 26th and this brought 7" of low density snow to valley bottoms and 10" above treeline.  This snow fell on a layer of surface hoar, which is now buried around 4-6" deep under the settled storm snow. Moderate to strong Northerly ridgetop winds during and after last weekend's snowfall has affected the snow in the Alpine, creating hard wind slabs, sastrugi and scoured areas.  Several natural avalanches occurred in sync with the snow and wind on January 26th, over a week ago.  These avalanches were all relegated to the storm snow and did not appear to step down into deeper weak layers in the snowpack.  Since then, there have been no observed or reported natural or human triggered avalanches.  Despite this, keep your guard up, practice safe travel techniques, and watch for wind slabs that could be sitting on weak snow underneath. More on this below.

This weekend, clear and cold temperatures with no precipitation is forecast. Looking ahead to the work week, temperatures should warm back up to the teens with a chance for snow starting Monday night.  Any new significant snow amounts will fall onto a very weak surface, and a very weak snowpack in general with several buried persistent weak layers.  If this becomes the case, watch out for red flags like recent avalanches, shooting cracks, whumpfing, and rapid loading as indicators to stay out of avalanche terrain.

This report is a weekly summary, so PLEASE be sure to follow the Turnagain Pass advisory for current weather and avalanche conditions. 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!


Primary Concern

As mentioned above, the snow from the Jan. 26th storm fell onto a widespread layer of surface hoar and facets. In areas exposed to wind, scattered wind slabs have formed and could be sitting on this layer of buried surface hoar just 6" to a foot deep. This is our main concern for a person finding and triggering a slab avalanche up to a foot in thickness.  Fortunately, there are a number of tools to help identify and evaluate this avalanche problem, which are wind slabs sitting on weak snow:

  • Keep your eyes open for wind affected features such as pillowed surfaces
  • Feel for hollow sounding, harder snow under your feet
  • Probing with your pole and hand pits are good ways to feel for strong snow over weak snow - signs a slab is present 
  • Stepping above the skin track to see if you can push little pieces of slab onto the skin track
  • Jumping on small, no-consequence test slopes 

It is also good to remember that at the base of the snowpack at the upper elevations, weak basal facets persist. While triggering an avalanche that breaks near the ground is unlikely, it is not out of the question on high elevations steep and rocky slopes (above 3,000'). 

In areas unaffected by wind, particularly below treeline, the snow is loose and sits on a crust. In steep terrain, the potential for loose dry avalanches exist in sheltered zones. Additionally, watch for cornices, these remain on the smaller side in general, but they still deserve a wide berth and can break farther back than expected.

 

 

Certain tools can be utilized to identify slabs as you travel, like stepping above the skin track to see if you can push little pieces of slab onto the skin track

 

The snowpack is still comprised of poor structure, with weak basal facets near the ground.  While triggering an avalanche on this layer is unlikely, it is still possible above 3000' near convexities and exposed rocks.

 

Any new snow that falls this week will fall onto a widespread crop of new surface hoar.  Above treeline this surface hoar is perched atop a variety of hard wind affected surfaces, including sastrugi, wind slab, breakable wind crust, and old melt freeze crust.

 


Mountain Weather

The weather during the past week has been cold and clear. Temperatures in valley bottoms have fluctuated from the teens to negative teens F and temperatures at ridgetops have fluctuated from teens to single digits.  Northerly ridgetop winds have average in the low 20's mph with top speeds bumping up to 30's twice during the week. Valley bottoms have been generally calm with the exception of light North winds the 31st.

Next week, temperatures should increase back to a pattern of overnight lows in the teens F and highs in the twenties. There is a chance of light snow showers starting Monday night. Light winds are expected at ridgetops on Saturday from the NE and then trend toward light and variable the remainder of the week.

Stay tuned to the CNFAIC weather page for an updated weather forecast each day. 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 temperature information. This weather station is in a sheltered area and wind data is typically less than the actual ridgetop winds. Also look at Sunburst Weather Station in Turnagain for a comparison.

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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