ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Tuesday March 19th, 2019
Posted by Aleph Johnston-Bloom on 03/19/19 at 7:00 am.
The Bottom Line
Considerable Avalanche Danger
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

The avalanche danger is  CONSIDERABLE  today.   Very large avalanches occurred naturally Sunday and Monday  sending debris far into runout zones and through flat areas.  Slopes  are loaded with 8 to 15 feet of snow.  Today is a break between storms. However, natural avalanches are still possible and human triggered avalanches are likely  today.   These could be very deep and dangerous and extra caution is advised.   Give cornices a wide berth. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.  

PORTAGE VALLEY:    Travel in runout zones from avalanches including venturing along and past the Byron Glacier Trail continues to be not recommended.  

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):    Large to very large human triggered avalanches remain likely. Between 2-3 feet of snow has fallen onto a very weak snowpack and avalanches are releasing in old buried weak layers.

SEWARD/LOST LAKE:    Large and dangerous natural avalanches  have been observed in this area. Today human triggered avalanches are likely in this region as well.    

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

Special Announcements

  • Turnagain Pass 20 years later:  On  Saturday, March 23rd from 12-2pm  swing by the Turnagain Pass moto lot and meet the CNFAIC avalanche forecasters, bring and test your avalanche rescue gear and learn about the history of Turnagain Pass and the CNFAIC. We’ll even have a few beacons buried so you can test your skills before heading into the hills!
  • Feeling sporty? Want to support avalanche education in Alaska? Head to the Alaska Avalanche School Ski-Mo (uphill/downhill) fundraiser race at Arctic Valley on Sunday, March 24th at 1pm. For more information click HERE. Great fun! Great cause!
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

Yesterday the large natural avalanches kept occurring with notable avalanches observed in Crow Creek, on Tincan, Seattle Ridge, Petes North, Twin Peaks, and through Summit Lake. These had very deep crowns, and were running into the flats in many locations. This was the second day in a row of very large slab avalanches. Today is a break in the barrage of storms after 6 days of HIGH avalanche danger. Temperatures are dropping this morning but are expected to rise again this afternoon and it should be partly sunny today. The natural avalanche activity should decrease but the potential for a very large human triggered slab avalanche remains. The current snowpack needs some time to adjust to all the loading from multiple feet of snow, strong winds and rain. Be patient! We are optimistic that at some point it will stabilize but today is definitely not the day test it out.  Choose terrain very wisely. The slabs could be very deep, there may be no signs of instability and it could be the 1st or the 10th skier or snowmachine on the slope that triggers the avalanche.  Avalanches could be triggered remotely from thin spots. In addition, pay attention to solar warming and the potential for roller balls and wet loose avalanches on sunny aspects. 

Tincan avalanche. Occurred sometime between 12:15-12:25 pm. 3-18-19. Photo: Corey Anderson

 Avalanche to the ground on Seattle Ridge, 3-18-19. 

Large avalanches, Templeton – Summit Lake, 3-18-19. 

 

Additional Concern
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
  • TYPE
    Cornice

Stay away from cornices. They have grown large and could be very tender and dangerous today. Triggering a cornice fall also has the potential to trigger a deep avalanche on the slope below. 

Mountain Weather

Yesterday: Mostly cloudy skies and rain/snow showers on and off throughout the day favoring Portage and Girdwood. Temperatures were in the 30Fs and 40Fs. Winds were northeasterly 15-25 mph with gusts into the 50s. Overnight skies became broken and temperatures dropped slightly. Easterly winds decreased blowing in the teens with gusts into the 30s.  

Today:  Partly sunny skies with temperatures in the 20Fs to high 30Fs. Sea level temperatures will be around 40F. Winds will be easterly 5-15 mph with gusts into the 20s. Clouds move back in tonight and winds pick up early morning Wednesday as the next warm wet storm moves over the region. Snow should start overnight.  

Tomorrow: Mostly cloudy with rain and snow showers that could be heavy at times. Rain/snowline is forecasted around 2000′. Easterly winds blowing 20-30 mph gusting into the 50s. The warm wet pattern is forecast to continue into the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35    0     0.1     88  
Summit Lake (1400′) 37   0   0.1    30
Alyeska Mid (1700′) 34   0   0.46     78  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  25     NE   20    62
Seattle Ridge (2400′) 30   *N/A    *N/A *N/A