ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Saturday March 2nd, 2019
Posted by Wendy Wagner on 03/02/19 at 7:00 am.
Avalanche risk
The Bottom Line
Low Avalanche Danger
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

There is a generally LOW avalanche danger in the Turnagain, Girdwood and Portage areas. Triggering a slab avalanche is unlikely. Watch for sluffs on steep shaded slopes and give cornices a wide berth. Glide cracks are moving, minimize travel under them as they can release at anytime.

SUMMIT LAKE / SILVERTIP:   More caution is advised south of Turnagain Pass as the snowpack is thin and harbors old weak layers. There is potential for a person to trigger a slab avalanche on steep slopes. See additional concerns below.

PORTAGE LAKE and BYRON GLACIER TRAIL:    Heads up that thin ice has been reported on Portage Lake. Additionally, the popular snow cave past the end of the Byron Glacier Trail is very dangerous and unstable. If you didn’t see  this video from February check it out.

1. Low
Alpine
/ Above 2,500'
Avalanche risk
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1. Low
Treeline
/ 1,000'-2,500'
Avalanche risk
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1. Low
Below Treeline
/ Below 1,000'
Avalanche risk
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Special Announcements

  • Take a minute out of your backcountry day to help the Community Snow Observations crew with gathering snow depth information in Alaska!! Website is  communitysnowobs.org. It’s easy to do, you just need a smart phone, 30 seconds and your probe to measure the snow depth.
  • Springtime has hit Hatcher Pass as well – check out today’s advisory HERE!!
Avalanche Problem 1
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
  • TYPE
    Normal Caution

After 8 days of brilliant sunny skies and springtime temperatures, a few clouds and cooler air is slated to move in today. The decrease in temperature will limit wet avalanche activity on south facing slopes and avalanche danger has dropped to Normal Caution (LOW danger). Over the past week, avalanche activity has been related to afternoon warming on southerly facing slopes. This triggered a number of wet loose slides, a few moist slabs and a few glide avalanches. As the southerly slopes now sport a solid sun crust, which may not soften today, and wet avalanches are not expected, glide avalanches are the exception moving forward. Things to keep in mind if you are headed out today:

  • Glide avalanches – Several small glide cracks released yesterday. These types of avalanches are highly destructive, unpredictable and not associated with human triggers. It’s always best to watch for and limit exposure under glide cracks.
  • Dry-loose sluffs – Loose surface snow exists in steep shaded terrain. Dry sluffs can move faster than expected or knock a person over.
  • Cornice falls – As always in mountain travel, give cornices a wide berth. 
  • An outlier slab avalanche – Although it is unlikely a person could trigger a slab avalanche, the mountains can harbor surprises, especially in thin snowpack areas. Considering the consequences before entering into high consequence terrain and maintaining good travel protocol are good habits that could pay off one day.

 

Glide avalanches on the lower portion of Raggedtop Mtn, releasing yesterday (3/1). Photo taken from Girdwood.

 

Recent wet loose avalanche activity in upper Glacier Creek / Girdwood Valley. 

Additional Concern
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
  • TYPE
    Persistent Slabs

South of Turnagain – Summit Lake and Silvertip zones:  For anyone traveling in this area note that a shallow snowpack with a generally poor structure exists. A variety of old weak layers (facets and buried surface hoar) sit in the mid and base of the snowpack. It is uncertain as to how reactive these layers are at this point and if they could produce a slab avalanche. We do know whumpfing has been observed in the Summit area and last Thursday’s (2/21) wind event triggered many large slab avalanches breaking in deeper weak layers. Assessing the slab as well as the weak layer will be important. Old wind slabs in steep terrain sitting on weak snow are the most suspect places to trigger an avalanche.

Mountain Weather

Yesterday:   Sunny skies with light and variable winds were over the region. Temperatures climbed into the mid 30’sF along the high peaks and mid elevations, while valley bottoms reached 30F. Overnight, temperatures have only dropped to the teens at most low elevations while ridgetop temperatures have dropped to the teens as well – limiting the inversion.

Today:    A few clouds are slated to move in today along with a chance for valley fog. The ridge of high pressure is weaker and that has decreased temperatures in the Alpine and increased them at sea level. Daytime highs should reach the mid 20’sF along ridgelines and the mid 30’sF in the low elevations. Ridgetop winds will be light from the east, 5-10mph.  

Tomorrow:   Mostly cloudy skies with a chance for a snow flurry or two will be over the area. No accumulation is expected. Mountian temperatures look to remain in the teens to 20’sF while ridgetop winds will be light from the east.  


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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29   0   0   59  
Summit Lake (1400′) 21   0   0   28  
Alyeska Mid (1700′) 30   0   0   54  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 30   E   3   10  
Seattle Ridge (2400′) 30   E   5   12