Snow & Avalanche Weekly Summary

Summit Area
Forecaster:   CNFAIC Staff  
Saturday, March 17th 2018
Created: Mar 16th 13:46 pm
Summary and Current Conditions

***Due to dangerous avalanche conditions across the region. The Chugach National Forest Avalanche Information Center has issued a Special Avalanche Bulletin through the weekend for Turnagain Pass and the Kenai and Western Chugach Mountains in and around Eastern Turnagain Arm. 

Stormy weather last weekend brought 1-2 feet of snow and strong winds to Summit Area. The new snow fell onto the thin Summit snowpack and formed a slab over many persistent weak layers, creating a dangerous avalanche prone set-up. Additionally sunshine and warm temperatures rising into the upper 30Fs and low 40Fs since Monday have contributed to the overall snowpack instability across the region. Monday a large avalanche was skier triggered remotely on Raven's Ridge from the skin track, Wednesday there was a skier triggered avalanche on Silvertip (just north of the Summit Area), and throughout the week observers have reported numerous natural slab and wet loose avalanches on most aspects and elevations. Clearing skies and warm temperatures over the weekend could again increase the potential for wet loose avalanches on solar aspects (South and East) and the likelihood of triggering slab avalanches on all aspects. Avoid traveling on or underneath 30 degree slopes and be aware of the consequences if the slopes slides. Be wary of even small terrain with high consequence runouts into terrain traps like the Silvertip avalanche. Be on the lookout for recent avalanches, whumpfing/collapsing, shooting cracks, rapid warming to temperatures above freezing, and rapid loading from new snow or wind.These are all red flags for dangerous avalanche conditions.  Keep in mind that the current persistent slab avalanche problem may not provide any red flags before an avalanche is triggered. A cautious mindset is warranted if traveling in Summit Area. Pay attention to changing conditions. Don't count on the luck of the Irish to keep you safe this St. Patrick's day weekend or into the week! For a shamrock of a day in the backcountry watch your slope angles. 

Warm temperatures into the mid to upper 30Fs are expected in valley bottoms with temperatures in the upper 20Fs at ridgetops this weekend.  Saturday should be mostly sunny and Sunday is forecast to become cloudy. There is a chance of precipitation starting Sunday and into Monday.  Looking into the work week there is some uncertainty, but weather models are pointing towards colder temperatures with either a chance of precipitation or clearing, sunny skies.  Highs are expected to be in the 20Fs with lows in the teens to single digits.  Winds look to be mostly light and variable. 

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

The 1-2 feet of snow that fell last weekend has settled into a strong slab of cohesive snow on top of a thin snowpack containing numerous persistent weak layers.  We have had widespread slab avalanche activity in the Summit Area since the last storm including the remote triggered avalanche on Raven's Ridge, the skier triggered avalanche on Silvertip (north of the Summit Area) where all three members of the group were caught on the slope, two large natural avalanches between Twin Peaks and Moose Mountain, three large natural avalanches on Fresno, and a natural avalanche on Lonestar. Persistent Slab avalanches have been reported on just about every aspect this week. The majority of the activity was observed in terrain between 1500'-3000' in elevation but this does not mean the upper Alpine is not suspect. Snow pit tests are failing across many different weak layers, showing the potential for triggering an avalanche down 1-2 feet. Avoiding traveling on or under terrain steeper than 30 degrees will be key to avoiding this avalanche problem and remember remote triggering is possible. Even small slopes steeper than 30 degrees with high consequence runouts into terrain traps, have the potential to bury a person.  The snowpack is expected to be most tender and avalanche prone this weekend during the warm, sunny weather forecasted.

A 1-2 foot slab sits on numerous weak layers in the snowpack.  These weak layers continue to be reactive in stability tests and are another indication of an unstable snowpack. 

The large avalanche on Raven's Ridge (just North of Butch Mountain) was remotely triggered from the skin track on looker's left on March 12th. Photo: Patrick McCormick.

Even a small steep slope can have high consequences if swept into gullies, trees, or alders. The Silvertip slide March 15th illustrates small terrain with high consequences. 

Zoomed in on the Silvertip crown. Photo:Mike Ausman

 Large natural avalanches on the South side of Fresno reported Sunday.


Secondary Concern

This past week warm spring temperatures and sunny days have destabilized the surface snow on solar aspects and lower elevation terrain. Natural small to large wet loose avalanches were reported on Southwest aspects of Moose and Lonestar.  This weekend wet loose avalanches are possible on steep solar aspects due to the forecast for above freezing temperatures and sunny skies.  Feeling the snow getting sticky and wet and seeing roller balls off of steep slopes will be obvious clues to that it's time to avoid solar aspects. Freezing temperatures at night have formed melt freeze crusts on solar aspects and in lower elevations that became saturated during the warm days. Paying attention to crusts forming and then melting again is very important to this time of year. Wet loose avalanches can be enough of a trigger to release a larger slab as slopes heat up. Avalanche hazard can increase quickly with water moving through a snowpack with persistent weak layers.

Additional Concern:

Cornices: Cornice falls triggered slab avalanches on Butch mountain this week.  Direct sunshine and warm temperatures can trigger this avalanche problem or make cornices more tender and easy to trigger. Avoid spending time underneath cornices and give them a wide berth as they can break back further than expected.  A cornice fall could trigger an avalanche on the slope below with the possibility of stepping down into deeper, buried weak layers. 

Natural wet loose avalanche on Lonestar observed Thursday the 15th. 

Natural wet loose avalanches from East side of road on Northern end of Summit area reported Thursday the 15th

 1" thick melt freeze crust observed on the Southwest aspect of Tenderfoot at 2200'.


Mountain Weather

Last weekend's storm brought 1-2' of snow and strong winds to the Summit Area. Winds from the NW and SE have averaged 10-20 mph and gusted into the 30s. Ridgetops temperatures have ranged from the teens increasing to the upper 20Fs later in the week.  Since Monday temperatures in valley bottoms have hit upper 30Fs and low 40Fs every day, returning to below freezing at night.  The skies cleared Monday and Tuesday and cloudy skies returned to the region Wednesday. There was light snow for periods Thursday with trace accumulation.

Saturday mostly sunny skies, calm winds, and warm temperatures are expected with highs in the upper 30Fs at valley bottoms and high 20Fs to low 30Fs at ridgetops. Temperatures are expected to drop below freezing at all elevations Saturday night. Sunday brings a chance of snow, cloudy skies, and temperatures with highs in the mid 30s F at valley bottoms and upper 20s F at ridgetops. Sunday night into Monday there is a chance of snow and cloudy skies with slightly cooler temperatures.  Looking later into the week there is some uncertainty in the forecast.  It is predicted that a high pressure system with colder temperatures and sunny skies will dominate the region but there still exists a chance for precipitation.  Temperatures are expected to drop through the week with highs in the 20Fs  and lows in the teens and single digits.

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: Mar 15, 2018 )

Glacier District
Johnson Pass: Open
Placer River: OpenPlease avoid private property and AKRR job site at Luebner Lake. Cross railroad tracks if needed, do not ride down tracks, it is illegal.
Skookum Drainage: OpenCross railroad tracks if needed, do not ride down tracks, it is illegal. FYI, Skookum drainage closes to Snowmachines on 4/1 as per the Chugach NF plan.
Turnagain Pass: Open
Twentymile: OpenCross railroad tracks at designated spot as you leave the parking area.
Seward District
Carter Lake: Open
Lost Lake Trail: Open
Primrose Trail: Open
Resurrection Pass Trail: OpenResurrection Pass trail is open to snowmachine use during the 2017/18 winter season.
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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