Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, April 4th, 2017 - 7:00AM
Expires
Wed, April 5th, 2017 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A  BACKCOUNTRY AVALANCHE WARNING has been issued through the National Weather Service  for the Turnagain Pass area and surrounding mountains.  Another round of rain, snow and wind will keep the avalanche danger pegged at  HIGH again today. Large natural avalanches are expected at all elevations while this storm system persists.  Travel is not recommended in avalanche terrain. If choosing to play in the flats, make sure to steer well clear of gullies and the bottom of steep slopes in the event an avalanche releases above you.

Hiking in Portage Valley:   Beware: avalanches occurring at the higher elevations can send large amounts of debris well into valley bottoms and cover snow-free hiking trails. Avoid trails that cross under avalanche paths.  

Summit Lake:    Travel in avalanche terrain is not recommended.  Read the  Saturday Summit Summary  HERE.

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Tue, April 4th, 2017
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Today we will see the brunt of the third storm to impact the area since March 27th. Winds are currently gale force from the East along ridgetops and .75-1″ of rain has fallen overnight up to 1,000′. For snow, this equates to the higher elevations accumulating between 1-2+ feet; the mountain landscape will have a much different look when skies finally clear. Another spike in natural avalanche activity is expected today and paths that have already released may be reloading and release again. Storm snow avalanches may also step down into weak older layers in the pack, creating an even larger slide. Add warm temperatures and rain to the mix and there is no question, avalanche terrain should be avoided.

How much load is on the old weak surface from March? Storm totals (March 27 – 6am April 4th):
Turnagain Pass:     3.0″ of H2O, 42+” of snow at upper elevations
Girdwood Valley:    4.2″ of H2O,  50+” of snow at upper elevations
Summit Lake:         1.1″ of H2O,   12-15″ of snow at upper elevations   

Large amounts of debris are running to valley bottoms during this storm cycle. Thank you to Turner Pahl for sending in this photo from the north side of the Skookum Valley (just below the toe of the Skookum Glacier). We are unsure of when this specific avalanche released but the photo was taken yesterday.

 

Again, if choosing to brave the roads and parking lots and play in the flats, please remeber to stay well away from slopes and runout zones – debris can run further than you think during storms like this!


Avalanche Problem 2
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

The rain/snow line has climbed from near sea level yesterday to 1,000′ overnight, possibly up to 1,500′ in places. Although we already saw a widespread natural wet slab cycle at 1,500′ on April 1st, we could see another one again today as another round of rain on snow is expected at the lower elevations. Hopefully the visibility will be good enough to see some of the action happening, but as is often the case, much goes unseen. 

Snow pit at 2,000′ at Turnagain Pass on Sunburst, April 2nd. Note the wet layers up to 2,000′, they only become wetter at the lower elevations where we are expecting wet avalanches.


Additional Concern
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

Prior to this storm cycle the snowpack consisted of many weak layers of facets and buried surface hoar. As mentioned above, avalanches releasing in the storm snow have the potential to ‘step down’ into old layers where snowpack tests are still showing propagation potential. Today’s strong winds and precipitation are likely to tip in the balance in the upper elevations and we could see an avalanche breaking in the mid-pack or near the ground, with crown depths over 6′ and running the entire length of a slide path

Weather
Tue, April 4th, 2017

Obscured skies filled the region yesterday with light flurries and rain to 100′ before the main portion of the storm moved in late in the day. Most of the action is from overnight when ridgetop winds picked up to the 40’s and 50’s mph with gusts in the 80’s from the East. Over 1″ of rain fell to 1,000′ at Turnagain Pass with .75 in the Girdwood Valley. This equates to 1-2+’ of snow at the upper elevations over the past 24-hours. Temperatures have been warm and fluctuating – sea level upper 30’sF, 2,000′ the lower 30’s F, ridgetops in the mid 20’sF.

Today, we should see continued precipitation with .6″ of rain below 1,000′ and 6-10″ of snow above 1,500′. Tonight another .25 of water is expected. The rain/snow line is tough to forecast and it could drop to 500′ and even lower if colder air slides in. Ridgetop winds will remain strong in the 30’s and up to 40mph from the East with higher gusts. Temperatures should remain warm, up to 40F at sea level, in the 30’s at the middle elevations and 20’s F along ridgelines.

This storm looks to stall out and churn through tomorrow and into Thursday bringing continued, but lighter, precipitation and strong Easterly winds.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   12   1.1   89  
Summit Lake (1400′) 34   2   0.3   30  
Alyeska Mid (1700′) 33   1   0.75   75  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE    37 82  
Seattle Ridge (2400′) 26   sensor rimed   sensor rimed     sensor rimed    
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Riding Areas
Updated Mon, December 02nd, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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