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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, March 8th, 2015 - 7:00AM
Expires
Mon, March 9th, 2015 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a MODERATE avalanche danger today in the Turnagain Pass region where 8-10″ of new snow and wind has formed sensitive wind slabs. These slabs are expected to be 8-14″ thick and easy to trigger on slopes over 35 degrees. In areas where the wind has not affected the snow, sluffs should be expected and large enough to be a legitimate concern in steep and sustained terrain.

Keeping a close eye on the new snow and watching for, and avoiding, any wind loaded slopes will be the key for a fun powder day.

***If you are headed to Hatcher Pass today, there is a HIGH avalanche danger.  Please see the Hatcher Pass Avalanche Center website for more details.

Sun, March 8th, 2015
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
More info at Avalanche.org

Could we really see a hint of winter now that we are well into March? Now that we just switched over to Daylight Savings Time? Why not… It seems like all bets are off these days and we will take what we can get! Below are mid-elevation storm totals from a cold front that moved over Alaska Friday night through yesterday:

Turnagain Pass – 10″
Girdwood Valley – 8+”
Summit Lake – 3-6″
Hatcher Pass – 12-18″

WIND SLAB:
On the heels of this much anticipated new snow has been a cold Northwesterly wind. The winds produced plumes off some, but not all, peaks in the region yesterday afternoon and have continued to blow in the 15-20mph range overnight. This is prime speed for wind slab development and human triggered wind slab avalanches should be expected. Additionally, this flow direction is ideal for loading the East face of Seattle Ridge.

Yesterday, we were able to find and trigger a small wind slab just before the winds kicked up. Today, these types of avalanches should be a dime a dozen and easy to trigger. Slab depths are on the shallow side, 8-14″, yet could be stiff enough to support the weight of a person; this is concerning as the slab may allow someone on to it before breaking above them. The good news is, wind slabs should be easy to identify with their smooth rounded surface and upside down feel (harder snow over softer snow). Quick hand pits are a great way to see how the new snow is acting and I’d recommend a number of these as you move through the mountains. 

Photo below is of an easily skier triggered soft wind slab yesterday on Sunburst’s Southwest face (3,000′ average depth 10″). 

 

Winds transporting snow on Mount Alpenglow yesterday afternoon.

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Watch your sluff. Sluffing in Friday/Saturday’s storm snow was prevalent yesterday and will be again today. These sluffs are entraining a significant amount of snow on sustained steep slopes and in channeled terrain. The cold temperatures will help to keep sluffs on the radar.

Weather
Sun, March 8th, 2015

It is very nice to finally have some new snow to report. Besides the storm totals above, see the chart below for the past 24-hour totals. The rain/snow line with this event hovered between 500 and 1,000′ and 3″ of wet snow (which has now frozen) fell at the parking lots at Turnagain. Snowfall shut down around noon yesterday and was followed by a switch in wind direction from the South to the Northwest. Cold air has and is currently being ushered in by the Northwesterly flow.

Today, visibility should be good with mostly sunny skies and a few lingering clouds. However, the cold Northwest winds are expected to remain in the 15-20mph range with higher gusts. Temperatures will continue to drop through the day into the teens at most locations, then to the single digits by tonight.

As we head into the early part of this week, no precipitation is expected as we will remain in a cold and blustery Northwest flow.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  28 3   0.3   45  
Summit Lake (1400′)  29 2   0.3   8  
Alyeska Mid (1700′)   30   2    0.27     29  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20   W   12   43  
Seattle Ridge (2400′) 23   n/a   13   42  
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.
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