ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Wednesday March 6th, 2019
Posted by Aleph Johnston-Bloom on 03/06/19 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 across the advisory area. Triggering a slab avalanche is unlikely. Watch for sluffing on steep shaded slopes, avoid travel under glide cracks and give cornices a wide berth. Pay attention to changing conditions.

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.

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Avalanche Problem 1
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
  • TYPE
    Normal Caution

Southeasterly winds kicked up yesterday averaging 5-10 mph with gusts into the high teens. This may have formed very shallow, small wind slabs in leeward terrain. Hopefully the wind was enough to knock over/blow away some of the surface hoar in exposed terrain but that is probably wishful thinking. In anticipation of snow, we have been closely mapping the surface conditions as well as watching for new surface hoar growth. Surface hoar has been observed from valley bottoms to the Alpine and is resting on a variety of surfaces. There is a stout sun crust on southerly facing slopes. On shaded aspects 4-8″ or so of soft near surface facets sit over a firmer base. Along ridgelines and areas affected by the NW wind events there is hard sastrugi, wind crust and/or rime crust. This set-up does not bode well for bonding when then next loading event does occur and the surface hoar gets buried. Cloudy skies, light winds and a chance of snow today should not change the avalanche danger yet. However, watch for changing conditions if more snow falls than forecasted. 

Today will be another day of Normal Caution (LOW danger). In addition to looking for mini wind slabs here are 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. South of Turnagain in the Summit Lake and Silvertip zones there is a shallow snowpack with a generally poor structure. A variety of old weak layers (facets and buried surface hoar) sit in the mid and base of the snowpack. The most suspect place to trigger an avalanche is steep terrain with old, hard wind slabs sitting on weak snow. 
  • Considering the consequences before entering into committing terrain and maintaining good travel protocol are good habits to keep on LOW danger days.

Surface hoar on a wind crust, Twin Peaks, 3-4-19. 

Surface hoar at 1600′ on Tenderfoot, 3-1-19. Photo: Jacob Kayes

 

Mountain Weather

Yesterday: Mostly cloudy skies with temperatures in the 20Fs to low 30Fs and no precipitation. Winds were southeasterly 5-10 mph with gusts into the high teens. Overnight winds became calm.

Today: Mostly cloudy with a chance of snow showers. Temperatures will be in the 20F and 30Fs. Winds will be light and easterly. More of the same overnight.  

Tomorrow: The day looks to start off similar to today with cloudy skies, chance of snow, light winds and temperatures in the 20Fs. Wind speeds and the likelihood of snow will increase in the late afternoon.   Overnight into Friday looks to be the beginning of the active pattern for the advisory area with up to a foot of snow in the forecast! Stay tuned for more details and think cold thoughts.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   0   0 58  
Summit Lake (1400′)  29      0      0    27    
Alyeska Mid (1700′) 28   0    0   52  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  18  SE  9 20  
Seattle Ridge (2400′)  23  SE  8  14