ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Sunday March 24th, 2019
Posted by Wendy Wagner on 03/24/19 at 7:00 am.
The Bottom Line
High Avalanche Danger
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

A  HIGH  avalanche danger remains over the region. Warm and wet weather continues to melt down the snowpack and cause large wet slab and wet loose avalanches to release naturally. These avalanches are occurring on slopes near and below 3,000′. They are gouging to the ground, running to valley bottoms at times and very destructive. Above 3,000′ storm snow avalanches and cornice falls are likely.  Once again, travel in avalanche terrain is NOT recommended.  

PORTAGE VALLEY:  Very large avalanches continue to release naturally. Avoid summer hiking trails that travel through avalanche paths, such as Crow Pass, Byron Glacier and Johnson Pass Trail.

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):   Despite less precipitation, natural and human triggered avalanches remain likely. The snowpack has many weak layers are currently being overloaded and stressed by warm temperatures and rain.  

SEWARD/LOST LAKE:  Similar to Turnagain – the hazard remains elevated as many wet slab avalanches continue to release.  Travel in avalanche terrain is not recommended.

4. High
Alpine
/ Above 2,500'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4. High
Treeline
/ 1,000'-2,500'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4. High
Below Treeline
/ Below 1,000'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Special Announcements

  • Headed to Hatcher Pass? Make sure and check our the HPAC Saturday advisory HERE!  
  • Looking for some exercise while supporting a great cause?? Today is Alaska Avalanche School’s  Ski-Mo (uphill/downhill) fundraiser race! This will be at Arctic Valley at 1pm. For more information click  HERE. Great fun!  
  • Got 5 minutes? Take  this short survey that is investigating who, how and where  Alaskans travel in the backcountry. Project lead by University of Alaska Southeast – more details HERE.
Avalanche Problem 1
Wet Slab
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
  • TYPE
    Wet Slab
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

One last cloudy and rainy day before skies finally clear and let the sun in. Today marks the 18th, and hopefully last, day of this impressive warm March storm series. Despite few folks in the backcountry and limited visibility yesterday, we know of six natural wet avalanches that occurred at Turnagain Pass. One was a wet slab just under Tincan’s CFR ridge, photo below. Another was a glide avalanche on SW facing Eddies Ridge and four were seen/heard by an Alaska Avalanche School Level 1 course. Of these four, three were seen on North facing Sunburst Ridge and one on SE facing Seattle Ridge. During the past 24-hours, close to an inch of rain fell in Girdwood Valley, 2.8″ in Portage Valley and almost half an inch at Turnagain Pass. Today, only .25″ is forecast yet avalanche conditions are expected to remain similar as even light rain on snow up to 2,000′ will keep the pack unstable.

A few things to consider for backcountry travel:

  • Know, and avoid, avalanche terrain. Give runout zones an extra wide berth. These wet avalanches can do wild things and run where we may not expect them to.
  • Glide cracks are opening and some are releasing. Limit/avoid being under cracks. New cracks have been seen in the Tincan Trees – photo below.
  • Cornice falls. Cornices are huge and have been growing and falling for two weeks now. Beware once skies clear!
  • Upper elevation storm snow problems. The higher in elevation the drier the snow – wind slabs, sluffs and storm slabs are all a concern. Direct sunlight this week could trigger large slabs in the Alpine. Heads up.
  • Shallow snowpack zones such as Summit Lake harbor many old weak layers (facets and buried surface hoar). Over the past few days numerous large wet slab and dry slab avalanches have released. These zones are just as dangerous, if not more, right now.

Looking ahead: Sunshine and very warm temperatures (even in the upper elevations) are in the forecast beginning Monday for the week. Avalanche danger may stay more elevated than one might expect. It is true once the snowpack begins to freeze it will lock up and limit avalanche activity. HOWEVER, the pack is incredibly wet and it will take more than one clear night to stabilize it for the morning hours. Of course, sunshine and warm ambient temperatures will quickly destabilize the snowpack again during the day/evening hours. Hence, springtime avalanche issues will be in full effect next week! Keep in mind upper elevations could produce some very large avalanches cornice falls during this warm and sunny period. The mountains do weird things in the spring and we need to be extra cautious with route selection, where we eat lunch, avoiding steep southerly slopes late in the day, and on. 

 

Wet slab avalanche releasing yesterday (Mar 23rd) off of Tincan’s CFR ridgeline, Westerly aspect at 2,000′. *Note the opening glide cracks in the trees lower on the slope. 


Wet slabs and wet loose avalanches wreack havoc on Seattle Ridge. Many steeper slopes has avalanched and many are hanging in the balance. 

Thanks to Alex McLain for snapping this photo of a wet slab on the shoulder of Moose Mtn in the Summit Lake area (near the Hope Y). The avalanche occurred sometime between 11am and 1pm yesterday, Mar 23rd. 

Mountain Weather

Yesterday:   Cloudy skies with light to heavy rain were seen below 2,500′ and wet snow above this. Just under an inch of rain was seen the Girdwood Valley and almost half an inch at Turnagain. Portage Valley was clearly favored coming in with 2.8″ of rain during the past 24-hours. Estimated snow totals at the high elevations are 8-10″ upper Girdwood Vally and 3-6″ at Turnagain Pass. Ridgetop winds were easterly in the 15-25mph range. Temperatures have decreased slightly this morning and sit at 35F at 1,000′ and in the upper 20’sF along ridgelines.

Today:   Mostly cloudy skies with light rain showers are expected over the region as one last low-pressure moves through. There is a chance we could see some breaks in cloud cover later in the day. Rain should fall up to 2,000′ with .25″ forecast (2-3″ wet snow at the upper elevations). Ridgetop winds should increase slightly to the 20-30mph range with stronger gusts from the East. Temperatures should stay in the mid-30’sF at 1,000′ and the upper 20’sF along ridgelines.  

Tomorrow:   Beginning Monday a high-pressure ridge will build in for the work week. This will bring clear skies and warm temperatures at all elevations; ridgetops could see 40F. Tuesday the upper elevation temperatures should climb even higher, possibly hitting the mid 40’sF along ridgetops during the peak of the day.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 37   0     0.4   73  
Summit Lake (1400′) 36   0    0.1 25  
Alyeska Mid (1700′) 35   0   0.85   68  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   NE   16   47  
Seattle Ridge (2400′) 32   SE   13   32