ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Monday November 26th, 2018
Posted by Wendy Wagner on 11/26/18 at 7:00 am.
The Bottom Line
High Avalanche Danger
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Continued snowfall and wind above 2,500′ will keep the avalanche danger at HIGH in the Alpine. Storm snow avalanches are expected again today at these upper elevations. At the mid-mountain elevations, rain falling up to 2,500′ will continue to wash away the snowpack and initiate wet avalanches on steep slopes where enough snow still exists.  The avalanche danger remains  CONSIDERABLE  in the treeline band as avalanches from above may run into these mid-elevations.  Travel above treeline is NOT recommended.

4. High
Alpine
/ Above 2,500'
Avalanche risk
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3. Considerable
Treeline
/ 1,000'-2,500'
Avalanche risk
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
0. No Rating
Below Treeline
/ Below 1,000'
Avalanche risk
Avalanche Problem 1
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.
  • TYPE
    Storm Slabs
  • Chance
    Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size
    Historic
    Very Large
    Large
    Small

Today we should see the third pulse in a series of warm storms impact the region. Temperatures climbed to 32F at 2,500′ yesterday, bringing rain as high as 2,200′. Today those numbers are expected to increase. Another 0.5″ of rain up to 2,500′ is forecast with 0.7″ tonight. In the alpine (above 2,500′) an additional 6-8″ of snow should fall today and 8-10″ tonight. Snow will be accompanied with winds in the 30’s and 40’s along the ridgetops from the east.

It is unknown the extent of the avalanche activity yesterday at the upper elevations due to limited visibility, but we did get a photo sent in to us of wet loose avalanches on the west face of Magnum at Turnagain Pass (thank you!). These avalanches were due to rain on snow, which will be expected again today. Obscured in the clouds at the high elevations we are expecting storm snow avalanche activity to continue. The new snow is piling up on a slick hard surface left from last week – which was a hard crust likely topped with surface hoar. This set up should be producing slab avalanches and as soon as the clouds part we’ll be doing our best to take stock. 

Storm totals at the mid-elevation snow stations for this soggy storm cycle:

  • Girdwood Valley at 1,700′:  4″ wet snow, 2,4″ of water equivalent (mostly in the form of rain)
  • Turnagain Pass at 1,880′:  16″ wet snow, 2.2″ of water equivalent (also seeing some rain)
  • Summit Lake at 1,400′:  2″ wet snow, 0.5″ of water equivalent (also seeing rain)

State of the snowpack? Although the snowpack is thickening in the high mountain terrain we are loosing the little snow that was there at the mid-elevations. Before this storm there was roughly 2-3′ of snow depth at 3,300′, that should be close to doubling after today’s snowfall. At 2,200′ and getting higher … bare ground is taking over as rain is washing away the few inches of snow remaining. 

 

Hard to see, but there are wet loose point release avalanches on the west face of Magnum, seen from the Center Ridge trail (Photo: Jacob Swartz).

Mountain Weather

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   3″ wet snow (with some rain) 1.2 15  
Summit Lake (1400′) 35   1   0.3   0  
Alyeska Mid (1700′) 35   Rain   1.9   0  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   NE   27   75  
Seattle Ridge (2400′) 32   SE   20    57