ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Monday April 1st, 2019
Posted by Aleph Johnston-Bloom on 04/01/19 at 7:00 am.
The Bottom Line
Considerable Avalanche Danger
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Another day of VERY WARM temperatures will increase the avalanche danger from  LOW  this morning  to  CONSIDERABLE  by this afternoon/evening. Dangerous wet loose, wet slab and glide avalanches may release naturally once the sun softens surface crusts and weakens the snowpack. All steep slopes above 1,000′ facing East, South and West that see direct sunshine should be carefully evaluated before traveling. Avoid being under glide cracks and give cornices an extra wide berth!  

PORTAGE VALLEY:   Summer trails with avalanche terrain overhead, such as Byron Glacier Trail and Crow Pass, are not recommended in the afternoon or evening due to the possibility of an avalanche occurring above.  

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):   Human triggered slab avalanches remain possible in upper elevation terrain on all aspects. This area has a thin  snowpack with many weak layers. High elevation sun-affected slopes are the most suspect for triggering a slab.  

SEWARD/LOST LAKE:   The snowpack is warming up and dangerous avalanche conditions are occurring late in the day in this area as well. A  large glide avalanche released on Mt. Marathon Thursday.  

3. Considerable
Alpine
/ Above 2,500'
Avalanche risk
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
3. Considerable
Treeline
/ 1,000'-2,500'
Avalanche risk
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
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

  • Warm conditions and large avalanches are occurring at Hatcher Pass as well.  Be sure to check out yesterday’s  Hatcher Pass Avalanche Center forecast  if you are heading that direction today.  
Avalanche Problem 1
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.
  • TYPE
    Wet Loose
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

Mid-March definitely came in like a lion with all the crazy weather and then March went out like an overheated lamb… Yesterday was the warmest day the advisory area has seen yet. Today should be very similar. Not only are the mid-elevations expected to see wet avalanches, we could see wet avalanche activity on sunny slopes in the high Alpine. Wet loose avalanches will be the most likely, but wet/moist slabs are possible.  The snowpack has already seen many days of a springtime melt-freeze pattern in the low and mid-elevations and with clear skies we did get a freeze overnight. However, with the intensity of the sun and the warm temperatures should be paying close attention to the potential for natural avalanches occurring in the afternoon/evening on solar aspects as crust break down and slopes get mushy. 

A safe day in the mountains includes planning ahead. Don’t be an April Fool! Know the terrain you are traveling on and under and if it will be affected by the sun. The boot test is a great way to assess how the daytime warming is, or is not, affecting the surface. If your boot easily sinks into mushy wet snow, it’s time to get onto shaded slopes or off the one you are on and well away from any runouts. Wet loose avalanches can start small from a person pushing soft wet snow as they ski or ride. If the terrain is large enough, this small slide can entrain snow and turn into a large and unmanageable avalanche. 

CORNICES: Cornices are very large and direct sunshine will destabilize them. A cornice fall has the potential to trigger an avalanche on the slope below and could break farther back than expected. 

Temperatures on Sunburst (3800′) over the last week.  Note the high temperatures yesterday and the lower RH indicating clear skies at night allowing for a solid freeze. 

The avalanche danger on steep slopes on the southern end of the compass will increase to CONSIDERABLE this afternoon/evening. Play the aspects for the best conditions and to stay safe!

 Avalanche carnage on the southerly slopes of Tincan and in the Library. Avalanches from the past week and the storm avalanche cycle the week prior.

Avalanche Problem 2
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 cracks are appearing throughout the advisory area and avalanching daily. Avoid traveling under glide cracks! Fresh glides avalanches were observed yesterday at 1:30 pm on Seattle Ridge and one was observed in motion at 4:30 pm on Tincan. The Seattle Ridge full depth avalanche that hit the uptrack Saturday is likely a glide that did not have a crack present before releasing; making our current avalanche situation more unpredictable. Remember, glides can release even if a hard surface crust is present (unlike the wet loose and wet slab avalanche problems). Many cracks are opening up in popular terrain and keep an eye out for them. 

Fresh glide avalanches observed at 1:30 pm yesterday, 3-31-19. These ran over old glide avalanches that released last week. 

 Glide avalanche that released on the uptrack on Saturday at 5:30 pm, 3-30-19. Photo: Travis Smith

Additional Concern
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
  • TYPE
    Deep Persistent Slabs

South of Turnagain in Summit Lake and areas in the interior Kenai Peninsula have a very poor snow structure with variety of old weak layers in the mid pack (facets and buried surface hoar.) Triggering a persistent slab 2-3’ deep as slopes warm in the afternoon sun is possible at the upper elevations. The avalanche seen on Butch Mtn. in Summit Lake last week is a good reminder that sunny hot days can surprise us! Keep in mind deeper weak layers could be lurking in these areas and sunlit slopes are the most suspect.

Mountain Weather

Yesterday: Clear and sunny skies with temperatures reaching as high as 40F at 4200′ and mid 50Fs at sea level. Winds were light. Overnight temperatures were slightly inverted with valley bottoms seeing high 20Fs and ridge tops low to mid 30Fs. Winds remained light.  

Today: Clear and sunny again with temperatures in the 30Fs to 50Fs and light northwest winds. Overnight temperatures will dip down again in the high 20Fs to mid 30Fs.  

Tomorrow: Clear and sunny with slightly cooler temperatures on tap for Tuesday and Wednesday. There is a chance of clouds on Thursday and maybe a little precipitation but the pattern change is still uncertain. Stay tuned! Finger crossed for spring powder???

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40    0 0   67  
Summit Lake (1400′)  34      0 0   21  
Alyeska Mid (1700′)  41      0 0    59    

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 36   variable   3    13
Seattle Ridge (2400′) 39    E 2    8