CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, April 27th 2017
Created: Apr 27th 6:16 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
Alaska Rock Gym
Special Announcement
  • This is the final week the CNFAIC will issue avalanche forecasts. These will be today and Saturday morning. We will be closing up shop on April 30th.
  • Observations: We will continue to monitor and post observations all spring and summer - so please keep us, and the community, posted on any snow/avalanche information you may come across on your upcoming adventures!
  • We have stopped issuing our Saturday Summit Summary for the 2016/17 season. Click HERE for our Springtime Avalanche tips.

The Bottom Line

The avalanche danger is MODERATE for today, but could increase to CONSIDERABLE by early evening. With daily warming human triggered wet avalanches will become possible on solar aspects this afternoon. Natural wet snow avalanches will also become possible later in the day. Additionally glide cracks continue to slowly creep open and can release without warning. Carefully monitor surface crusts throughout the day and be aware of steep terrain above you that may be heating up faster than you may expect.

There is a LOW avalanche danger below 1,000’ where little snow remains. The one exception is in the Portage/Placer area where there is potential for an avalanche from above to run into this zone. 

Hiking on summer trails during the springtime warm-up (including the Byron Glacier trail, Crow Pass, etc).  Extra caution is advised for trails that cross under avalanche paths and the danger will increase in the afternoon with daily warming. 

FRIDAY APRIL 28th AVALANCHE OUTLOOK: A MODERATE avalanche danger is expected again tomorrow during the day, but could increase to CONSIDERABLE if the sun comes out. The weather forecast for tomorrow is similar, overnight temperatures may dip slightly below freezing in the alpine and sky cover may vary from scattered rain showers to periods of sun. It will be in the afternoon and evening when the possibility for natural wet avalanches on solar aspects will increase. Please see the discussion below for more details.


Primary Concern

A slow and steady spring time shed cycle persists. This is where above freezing temperatures cause the snowpack to loose its strength and becomes wet and saturated releasing naturally or with the weight of a person/snowmachine. The last two nights we’ve seen temperatures dip below freezing again in the upper elevations - causing a crust to form. Unfortunately this re-freeze is superficial and clouds have kept some heat in and mid elevations temps are still above freezing. Today and tomorrow it will be important to monitor this crust and pay attention to how much the sun and/or rain showers break it down. This is the time of year when avalanches from above can catch you by surprise. Solar aspects in the afternoon and evening are most vulnerable. Be aware that steep rocky areas with thin snow coverage heat up fast and natural activity will be more likely in these areas - including slopes that have already seen lots of avalanche activity. For Friday: If skies remain cloudy overnight and temperatures remain above freezing in the alpine a surface crust on Northern aspects may start to melt, making wet avalanches possible on all aspects.  

WET SLAB, WET LOOSE and CORNICE FALLS:
Things to keep in mind if you are headed out: 

  1. Is the snowpack frozen or wet and soggy? A hard frozen snowpack is stable, a soft mushy snowpack is dangerous.
  2. Are you punching through a shallow crust into wet soggy snow? A shallow re-freeze is still weak and could avalanche.
  3. Are you seeing recent avalanches?
  4. Are you in a runout zone? Can an avalanche releasing above wash debris over your location? Avalanches can run into valley bottoms.
  5. Buried weak layers in the pack can make a small avalanche or sluff larger by propagating across the slope and/or stepping down.
  6. Wet avalanches are hard to escape if you get caught. A small slide can be deadly if it pushes you into a terrain trap.


Secondary Concern

Similar to the wet issues above, glide avalanches are also occurring with the springtime melt-down. Glide cracks are opening up and releasing on many slopes in the region - steer clear of any slopes harboring glide cracks. Check out the photo below from the motorized up-track. This slope is notorious for producing glide avalanches. Additional glide avalanche activity is expected today and through the week.


Additional Concern

There are several buried persistent weak layers in the snowpack; ranging from buried surface hoar 2-6' deep, mid-pack facets and facets near the ground. Shallow snowpack zones such as the Summit Lake area harbor depth hoar near the ground. On upper elevation North, West and Easterly aspects these weak layers could re-activate if the surface crust starts to melt and become wet on these aspects. If this melting occurrs triggering a larger natural slab avalanche may be possible.


Mountain Weather

Yesterday skies were partly clouding with scattered rain showers. Northerly ridgetop winds were light.  Day time temperatures reached a high of 55F in the mid elevations and 40F in the upper elevations. Late in the evening widespread thin cloud cover was observed across the forecast zone. Overnight temperatures reached a low of 29F in the upper elevations and 35F in the mid elevations.  

Today scattered rain showers will persist and patches of sunny skies are possible. Only a trace of precip (0.05") is expected today and up to 0.15" overnight. Daily temperatures are expected to reach the mid 50Fs in the afternoon and 40F in the upper elevations.  Overnight lows are expected to remain above freezing (mid 30F’s) in the mid elevations reach just below freezing (30F) in the alpine. Winds are expected to remain light from the North. 

A very similar weather pattern is expected Friday and into the weekend. Scattered rain showers and partly cloudy skies are expected vary accross the forecast region. Easterly ridge top winds may increase Friday night into Saturday, 15-20mph.

PRECIPITATION 24-hour data (6am - 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 45  54 
Summit Lake (1400') 41  13 
Alyeska Mid (1700') 41  .03  50 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 34  NE 
Seattle Ridge(2400') n/a  10 

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass 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: Apr 11, 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: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
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

Subscribe to the Turnagain Area Avalanche Advisory:

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.


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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC