ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Tuesday April 9th, 2019
Posted by Wendy Wagner on 04/09/19 at 7:00 am.
Avalanche risk
The Bottom Line
Moderate Avalanche Danger
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

The avalanche danger remains MODERATE  at all elevations. In the mid-elevations, glide avalanches continue to release sporadically and are creating a dangerous and unpredictable hazard. Limit any travel under glide cracks. Additionally, wet loose sluffs are possible on saturated steep slopes below 2,000′. In the Alpine, watch for areas with new wind-drifted snow where small wind slabs may be triggered on steep shaded slopes. And as always, give cornices a very wide berth.

GIRDWOOD VALLEY:   Between 4-6″ of new snow has fallen in the higher elevations of Girdwood Valley. Wind slabs up to 10″ thick along with dry/moist sluffs could be found on steeper slopes in the Alpine.  

PORTAGE VALLEY:   Summer trails with avalanche terrain overhead, such as Byron Glacier Trail, are not recommended due to the possibility of an avalanche or cornice fall sending debris over the trail.

2. Moderate
Alpine
/ Above 2,500'
Avalanche risk
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2. Moderate
Treeline
/ 1,000'-2,500'
Avalanche risk
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2. Moderate
Below Treeline
/ Below 1,000'
Avalanche risk
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Special Announcements

Avalanche Problem 1
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. The are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
  • TYPE
    Glide Avalanches
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

Glide avalanches continue to be the most concerning avalanche problem for anyone traveling in avalanche terrain. Glide cracks litter the slopes and could release into an avalanche at anytime. Cracks are predominatly opening at elevations below 3,000′ and on E, S and W aspects. They are not triggered by people and are very unpredictable and destructive to anything in their path. The last known glide crack to release into an avalanche was Sunday morning, just south of Turnagain Pass near the Hope Wye cutoff. What we can do is keep our eyes open and limit/avoid traveling under cracks (example photo below). This may take some creative route planning in places, but it could be well worth it if a crack decides to release in your vicinity.

WET LOOSE:  Triggering a wet loose avalanche (sluff) on steep slopes that did not freeze overnight is possible. This will be most likely on slopes below 2,000′ that have been soaked by rain and remain wet and unsupportable. 
 

Glide cracks on Tincan under Common Bowl. 

Avalanche Problem 2
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
  • TYPE
    Wind Slabs
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

It may be wet and raining down low, but it’s still relatively dry up high. Above 2,500′, anywhere from 1-6″ of new snow fell over the region yesterday (favoring Girdwood) which was added to the 3-6″ of new snow from over the weekend. Plug in moderate easterly ridgetop winds and we can expect 4-10″ thick wind slab on leeward facing slopes. Shaded aspects will be the most touchy as wind slabs are sitting on weak older snow (facets/buried surface hoar). One of these slabs was found on the North Chutes on Tincan Sunday (photo below). Keep a lookout for wind deposited snow, fresh drifts and watch for cracking around your skis/board or machine. Even a small wind slab can be a problem in steep rocky terrain.

Small, shallow skier triggered wind slab on one of Tincan’s north facing chutes on Sunday. (Photo Adam Baxter)

 

CORNICES: Cornices remain very large along some ridgelines in the Alpine. These cornices can break suddenly and pull back onto flat ground above a slope. Give them a wide berth and avoid travel directly below them.

South of Turnagain in Summit Lake and areas in the interior Kenai Peninsula still posses a variety of old weak layers within the snow pack. Be aware of a variety of avalanche conditions ranging from small isolated wind slabs to wet loose. Triggering a persistent slab 2-3′ deep is becoming an outlier at this point, but the poor snowpack structure is worth noting if headed to Summit.  

Todd’s Bowl and the North facing Chutes of Tincan at Turnagain Pass. Winter remains at these higher elevations. 

Mountain Weather

Yesterday:   Cloudy skies with light rain fell up to 2,000′ over the region. Girdwood picked up just under 1/2 an inch of rain, while Turnagain Pass saw around a tenth of an inch in the past 24-hours; this equates to 4-6″ of snow above 2,500′ and 1-2″ respectively. Ridgetop winds have been moderate, averaging 10-20mph with gusts near 40mph from the east. Temperatures climbed to the upper 20’sF at 4,000′ and the  mid 40’sF at 1,000′ before dropping to the mid 20’sF at 4,000′ and the mid 30’sF at 1,000′.  

Today:   Mostly cloudy skies, with a few breaks in cloud cover, are in store today as a weak low pressure spins in the Eastern Gulf. A few raindrops may fall up to 2,000′ with flurries above this in favored areas. No measureable precipitation is expected. Ridgetop winds should remain moderate from the east in the 10-20mph range with gusts into the 30’s at times. Temperatures will be on a slow decline as cooler air moves in and highs near 40F are expected at 1,000′, while ridgetops remain in the mid 20’sF.  

Tomorrow:   A brief break between systems should bring partly cloudy skies, mild temperatures and light easterly winds for Wednesday. A powerful front is forecast to hit the region Thursday bringing heavy rain, 4-10″ of snow above 2,000′ and 50-70mph winds. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 37   rain   0.1   63  
Summit Lake (1400′) 37    0 0   19  
Alyeska Mid (1700′) 35   0.5   0.42   57  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 27   NE   14   39  
Seattle Ridge (2400′) 31   SE   11   20