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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Tuesday, February 23rd 2016
Created: Feb 23rd 6:16 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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
Special Announcement

Mark your calendars for the second annual SNOWBALL this Friday (Feb.26th) at Taproot. This fun-filled, mid-winter fundraiser is a joint effort between the Alaska Avalanche School and the Friends-CNFAIC.  All proceeds directly support avalanche information and education in Alaska!  Iron those Carhartts, break out the sequins, and dust off the top hat…its Snowball time!  Tickets on sale at https://taprootalaska.com/


The Bottom Line

A CONSIDERABLE avalanche danger exists today in the alpine where fresh wind slabs will be of concern after a potent storm delivered 3-4+ feet of new snow in the alpine between Saturday and Sunday.  Cautious route finding and conservative decision-making will be essential today if venturing into the alpine.  Today will warrant hyper-vigilance if moving around cornices.  These are under tremendous stress right now in the wake of our most recent storm and will be even more so with a bump in easterly winds today.  

At treeline the danger is MODERATE where glide cracks are lurking under this most recent dump of snow.  Though many are not currently visible, make no mistake; these cracks litter the Turnagain pass zone between 1500 – 2500 feet.


Primary Concern

A quick tour to treeline on Tincan yesterday found significant avalanche carnage from the much publicized weekend storm.  Unfortunate for surface conditions, we found a breakable crust entombing 2 feet of settled storm snow up to 2,000 feet.  This crust appeared on the tail end of the storm as temperatures dropped Sunday night, and is acting to promote more stable snow in the mid-elevations (at treeline).  In the alpine however, soft, surface snow is abundant and will be ripe for transport today with winds forecasted in the 20 to 45 mph range.  Fresh wind slabs are likely to form on south and west aspects and may be 1-3 feet deep.  If travelling in the alpine, pay attention to changing surface conditions and drum-like or hollow sounding snow as this is indicative that you’ve found a wind slab. 

With limited visibility yesterday and no observations from the alpine since before the quick-hitting weekend storm, confidence is low that the storm snow is settling without incident.  Careful snowpack evaluation will be essential today if moving through the upper elevations to ensure you are managing terrain appropriately.

Storm slab/ wind slab just lookers left of Tincan proper looks to have avalanched at the tail end of the weekend storm.


Secondary Concern

Again, visibility hampered a good look into alpine start zones yesterday but given the state of cornices (large and mature) before this storm, you can bet that 4+ inches of water weight from the weekend and winds averaging in the 30’s mph have brought these backcountry bombs ever closer to their tipping point.  Avoid time spent below cornices and keep a healthy distance (and then some) away from the edge if travelling along a corniced ridge today.  Cornices now are as large as we’ve seen all season and have a tendency to break much further back than one might anticipate.  Given the sheer size and weight of any cornice failure today, it’s quite possible a cornice fall will initiate a slab on the slope below.  


Additional Concern

I spotted one new glide crack that appeared to have released mid-storm and maybe a hundred others that ‘disappeared’ during the storm.  Unfortunately glides are going to be difficult to see right now due to last weekends fresh snow, but make no mistake, these cracks are still scattered about in the backcountry, mainly in the 1500 – 2500’ elevation band in popular ski/ snowmachine terrain such as Seattle ridge, Main bowl, Tincan and others.  Glide cracks are growing larger by the day but still prove very difficult to forecast for.  Your best bet continues to be to map out where these cracks exist and limit you exposure time below. 

Pre-storm and post-storm photo of Seattle ridge from the motorized parking lot.  Notice the glide cracks in the upper image have all been buried with the subsequent storm.  Make no mistake, glide cracks do still exist and threaten a lot of well-travelled terrain on both the motorized and non-motorized side of the highway.


Mountain Weather

The short but intense storm that impacted south central Alaska wrapped up on Sunday night after depositing 2-4.5 inches of water weight from Summit Lake to Girdwood.  Yesterday, the Turnagain pass area was under a showery regime most of the day with just a few short breaks where the sun managed to poke through.  1-3” of new snow fell throughout the day as temperatures hovered right around 32F at 1,000 feet.  Winds were out of the NE in the teens and gusting to 30’s mph at ridgetops. 

Today we can expect ridgetop winds to increase in the 25-45mph range from the East.  Temperatures will be in the mid-30’s at 1,000’ promoting 2-4 inches of snow below about 1,300 feet. 

Yet another warm front spinning off a Gulf of Alaska low is expected to impact our area overnight tonight and through the remainder of the workweek, bringing warmer temperatures and more unsettled weather.  Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  30  3 .3  121 
Summit Lake (1400') 29   3 .4  40
Alyeska Mid (1700')  32  2 .2   98

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  22 ENE   18 45 
Seattle Ridge(2400')  25 n/a * n/a * n/a *

*Seattle ridge anemometer (wind) appears to be rimed up.

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

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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
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