ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Sunday March 3rd, 2019
Posted by Wendy Wagner on 03/03/19 at 7:00 am.
Avalanche risk
The Bottom Line
Low Avalanche Danger
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

A generally  LOW  avalanche danger remains for Turnagain, Girdwood and Portage areas. Although triggering a slab avalanche is unlikely, watch for sluffs on steep shaded slopes.  Glide cracks are moving. Minimize travel under them as they can release at anytime.  And as always, give cornices a wide berth.

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

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 can be very dangerous and venturing inside is not recommended.  

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

  • The Friends of the Chugach National Forest Avalanche Center is an  official Pick. Click. Give. organization.  When you apply for your PFD please consider supporting your public avalanche center. We rely heavily on your contributions, which provides not only weather stations and daily forecasts but a host of other public avalanche services. Thank you to all of our donors past, present and future!
Avalanche Problem 1
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
  • TYPE
    Normal Caution

Cloudy skies, cool temperatures and light winds will not impact avalanche conditions today and a Normal Caution (LOW danger) regime remains in place. The one exception is the glide avalanche. We have seen several small glide cracks release into avalanches in the Girdwood Valley and Turnagain Pass during the past two days. Although many of these slides are on the smaller side and in areas not commonly traveled, there are some current issues on Seattle Ridge. Several cracks have opened up along the ridge and one of these released Friday, Mar 1st. As far as the older glide cracks we’ve been monitoring in popular areas such as Magnum, Lipps, Cornbiscuit, these do not appear to be moving as quick. PSA: Help us keep track of these cracks and send us a photo! 

Things to keep in mind if you are headed into the backcountry:

  • Glide avalanches – These types of avalanches are highly unpredictable and not associated with human triggers. It’s always best to watch for and limit exposure under glide cracks.
  • Dry-loose sluffs – Watch your sluff on steep shaded slopes.
  • Cornice falls – As always, 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 to keep on LOW danger days.

Surface conditions? In general, a stout sun crust has been found on southerly facing slopes. Otherwise, 4-8″ or so of soft re-crystalized (near surface faceted snow) sits over a firmer base on shaded aspects. In anticipation of the next storm, we are closely mapping the surface conditions as well as watching for new surface hoar growth. 

  

The ‘State of the Glide Cracks’ along the front side of Seattle Ridge seen from the motorized parking lot.

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:   Overcast skies with light easterly ridgetop winds blowing 5-10mph. Temperatures stayed a cool 15-20F in the upper elevations, while lower elevations warmed to the mid 30’sF. Overnight, valley bottoms have only dropped to the upper 20’sF due to cloud cover limiting most radiative cooling.  

Today:   Cloudy skies with a chance for a few snow flurries will be over the region as a weak low pressure moves overhead. No snow accumulation is expected. Ridgetop winds are forecast to be light and variable. Temperatures along ridgelines should remain in the 15-25F range and lower elevations are likely to warm back into the mid 30’sF.  

Tomorrow:   A brief ridge of high pressure builds in for Monday. This should clear skies, keep temperatures cool and bring light winds. It will also provide one good visibility day before a large scale trough pushes several fronts over Southcentral bringing periods of snow and wind for the later part of the work week. Stay tuned!


STATE OF THE SNOWPACK:
  Charts below show both Snow Depth and Snow Water Equivalent (SWE) for Turnagain Pass. Main take home here is Turnagain Pass’s snowpack is just over half (57%) of what it typically is as of March 2nd. Large snowfall events can really help out the pack quickly, as they did last year, and many of us are hoping for a few of these events for March and April 2019!  

 


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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29   0    0 58  
Summit Lake (1400′) 23   0   0   28  
Alyeska Mid (1700′) 29   0   0   54  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19   E   5   13  
Seattle Ridge (2400′) 26   S   2   8