ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Friday April 5th, 2019
Posted by Wendy Wagner on 04/05/19 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 for glide avalanches. Glide cracks have been releasing into avalanches in many popular recreating areas and pose a hazard to anyone traveling under glide cracks. Additionally, human triggered wet loose avalanches are possible if southerly slopes warm enough to soften surface crusts. As always, give cornices a wide berth – they are quite large this spring.

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

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. Evaluate snow and terrain carefully.  

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

Cooler temperatures over the region have put a halt on the wet avalanche issues we had last week. Many slopes are covered with crusts and the avalanche danger has decreased dramatically. Despite this, the pesky glide avalanche problem has not gone away and is our main concern for anyone headed into the backcountry. Cracks keep opening up and releasing in popular areas. Humans do not trigger glide avalanches, which makes the problem unpredictable as they can avalanche at any time. The good thing is we can watch for, and avoid, being under opening cracks. This is a case of ‘don’t be caught in the wrong place at the wrong time’. These slides, even small ones, are extremely destructive.

Glide avalanche on Magnum’s SW face (PMS Bowl), releasing Tues Apr 2nd. This is a heavily traveled slope and an example of how a person may be caught in the wrong place at the wrong time.

Additional Concern
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
  • TYPE
    Normal Caution

Other than the creepy glide avalanche issue, the mountains are in a Normal Caution regime as far as avalanche danger. This means human triggered avalanches are unlikely. Some things to watch for and keep in mind if headed out today:

LOOSE WET:  If slopes in the sun (and out of the breeze) heat up enough today, wet loose sluffs could be triggered this afternoon/evening.

CORNICES: Cornices remain very large along some ridgelines in the alpine. Give them a wide berth and avoid travel directly below them, especially in the heat of the day.

South of Turnagain in Summit Lake and the interior Kenai Peninsula the snowpack is very thin with a poor structure. Triggering a slab 2-3’ deep is unlikely, but not out of the question. The most suspect slopes are in the alpine above 3000’ – on shaded aspects any time of the day or on steep solar aspects late in the afternoon if the surface crusts soften.

Mountain Weather

Yesterday:   Mostly cloudy skies were over the area with light rain in Girdwood (0.1″) and Portage (0.4″). Ridgetop winds over the past 24-hours have been light to moderate from the east averaging ~10mph with gusts into the 20’s mph. Temperatures have been steady in the 20’sF along ridgelines and in the 30’sF at 1,000′. Cloud cover overnight has limited cooling in valley bottoms and low elevation stations are reporting low 30’sF.

Today:   Partly sunny skies are expected today before clouds and light rain move back in tonight. Ridgetop winds are forecast to remain in the 10-15mph range with gusts to 30mph from an easterly direction. Temperatures look to stay mild, climbing to 40F at 1,000′ and the upper 20’sF along ridgelines.  

Tomorrow:   Stormy weather is expected as a low pressure spinning in the Gulf pushes a front over the Eastern Turnagain Arm. Rain falling up to 1,500′ or so is expected (possibly higher) with water amounts in the .25 – 1″ range. This equates to roughly 2-6″ of snow falling in the higher elevations. Ridgetop winds should pickup from the east as well. At this point, Sunday looks to remain cloudy and wet as the front stalls over before heading out possibly Monday. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33   0   0    64
Summit Lake (1400′) 33 0   0   21  
Alyeska Mid (1700′) 32   0   0.1   58  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  22 NE   11   26  
Seattle Ridge (2400′) 27   SE   6   18