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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, April 14th 2015
Created: Apr 14th 6:17 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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The John Byrne Family
Special Announcement

We are currently issuing advisories 5 days a week until our final advisory on Thursday, April 30th.  Advisories will be posted at 7 am each day except Mondays and Wednesdays.


The Bottom Line

The avalanche danger is MODERATE in the Alpine and the Treeline elevation bands for wind slab and loose snow avalanches associated with new snow instabilities. Up to 6" of snow, along with moderate Easterly wind, is forecast through the day with another 2-6" overnight. Wind slabs are expected to be 4-8" thick today and up to 14" by tomorrow. Additionally, there are a number of weak layers and interfaces buried deeper in the pack on all aspects where a small possibility exists for a large avalanche to be triggered.

AVALANCHE OUTLOOK for tomorrow, Wednesday:

Avalanche conditions are expected to be similar tomorrow as the storm slowly moves out. Light snowfall, adding another 2-4", is expected along with light Easterly ridgetop winds. Human triggered slab avalanches composed of the storm snow are possible along with widespread sluffs. If the sun comes out on Wednesday, wet loose avalanches on southerly slopes should be expected.


Primary Concern

After waiting for months, it seems winter is finally trying to show up. We have another storm system moving in today which is expected to add 2-6" of new snow and another 2-6" tonight - snow should make it to sea level. Avalanche conditions will be mostly related to how much new snow accumulates, however there are some concerning layers deeper in the pack to keep in mind (more on that below).

WIND SLAB and STORM SLAB:

Wind slabs forming on leeward slopes will be fairly shallow (4-8" thick) today. Even in areas seeing little new snow, these should build due to 6-8" of existing loose snow available for transport. With continued snowfall overnight, wind slabs could be in the 10-14" thick range tomorrow - which will be more of a concern. Areas out of the wind, where up to a foot of new snow may fall by tomorrow, could see slabs as well. If you are headed out, monitoring the new snow with quick hand pits and/or using your pole to check for stiffer/denser snow over softer/weaker snow will be good ways to assess slab development.

LOOSE SNOW AVALANCHES (SLUFFS):

Natural and human triggered sluffs are expected in the new snow on all aspects and elevations. When the sun comes out, possibly tomorrow, watch for wet/damp sluffs on Southerly aspects. 

CORNICES:

Cornices will continue to grow and fall naturally with this warm(ish) storm. 


Secondary Concern

The mountains are currently in a transition period from winter to summer which means a highly variable snowpack that changes dramatically with aspect and elevation. In short, Northerly slopes have weak faceted snow sitting anywhere from 2-8' below the surface; this spread is so dramatic due to the snowfall amounts during last week's storm. The South side of Turnagain Pass has a thinner snowpack and therefore these weak layers are more concerning. On Southerly slopes, a stout crust exists below the storm snow from last week (2-4' below the surface). Initial bonding was poor and though stronger now, still a concern.

What this all boils down to is: triggering an avalanche that fails deeper in the pack, although not likely, is not out of the question. Remember your safe travel protocol: expose one person at a time, have escape routes planned, watch your partners and know how to effect a rescue if a slide is triggered.


Mountain Weather

Mostly sunny skies and springtime temperatures filled the region yesterday. Winds were light and variable. Temperatures reached the mid 30's F in the sun mid-day before dropping back into the teens overnight.

Today and tonight, we will see a relatively weak storm roll in as a low-pressure, just South of the Aleutians, moves East. We can expect cloudy skies, 2-6" of new snow today with an additional 2-6" tonight. Ridgetop winds will increase from the East to 25-35mph with stronger gusts. Rain/snow line will be right around sea level.

For Wednesday, this low-pressure looks like it might stall out over the Kenai bringing the possibility for widespread instability showers. We could pick up another 2-4" of snow in some areas while others see sunshine. Ridgetop winds on Wednesday should be light, 5-10mph, from the East. 

Thursday looks to be a break between storms before another low moves in for Friday. Stay tuned on Thursday's forecast.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29 71 
Summit Lake (1400') 25  13 
Alyeska Mid (1700') 29  41 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 21  var  31 
Seattle Ridge(2400') 25   n/a 25 

 

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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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
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