Presidential Range

Avalanche danger remains elevated today with human-triggering of wind slabs possible in steep terrain where wind has drifted the recent snow. These avalanches could already be large enough to carry and bury a person, and will grow larger as new snow and wind loading occur later today and tonight. If “red flags” such as new or recent snow and wind loading create doubt about snow stability, choose a lower angled slope away from avalanche paths. Natural avalanches will become possible on easterly aspects as new snow accumulates this evening and wind shifts to the west.  Avalanche danger will rise to Considerable after dark. Today, the avalanche danger is Moderate with human-triggered avalanches possible. Evaluate snow, weather and terrain carefully.    

The human triggered avalanche yesterday in the Gulf of Slides bought some learning opportunities for the party of four involved. Several other parties in the area, including at least one avalanche class, were in similar terrain but were lucky enough to not trigger their own avalanche. The triggering party, all of whom had taken avalanche courses in the past two seasons, recognized that they were in heads-up conditions and wisely chose to reduce their exposure with cautious route finding. Unfortunately, they based their decision to proceed into that terrain on the fact that an extended column test did not propagate a crack. Their test, performed as instructed in every modern classroom, was performed on a safe location in lower angled terrain not exposed to the hazard. The missing piece of the puzzle is that stability tests are meant to be performed in locations representative of the slope and aspect meant to be assessed. This is a problem with wind slabs. 

They are not alone in drawing false conclusions on the basis of stability tests when dealing with a wind slab avalanche problem. It’s important to understand that snow stability tests are not an effective tool for determining the stability of an avalanche problem that, by its very nature, is extremely variable in its distribution (and thickness) across the landscape. If you find yourself confronted by a smooth pillowy snow surface that has developed due to new snow and recent wind loading, using any sort of snow pit test to determine slope stability is fraught with error. A wind loaded slope will have multiple trigger locations which will escape detection while digging your pit. Digging in the snow is important, but less so when assessing wind slabs, where slope configuration, snow structure and density are better indicators of potential problems. Taking red flags such as new snow or wind loading within 24 hours are better indicators of slope stability in cases like this and unfortunately for us in this range, these red flags are frequently flying.  Thanks and kudos to the party for debriefing their day efectively and then sharing their story with me and the observation with the community.

The avalanche that occurred in the Lip yesterday was reported and subsequently searched by snow rangers using Recco and beacons. While there were ski tracks on the surface of the debris, it was impossible to rule out human triggering of the slab from adjacent slopes from below since the debris wiped out these areas. Sadly, we continue to see skiers in the terrain without beacon, shovels and probes. The Gulf of Slides avalanche was a good reminder that you can bring a wind slab down on yourself from above, either while booting or by attempting a ski cut, which is a sketchy tool to use on that avalanche problem type. The Lip avalanche was small relative to path but was quite thick in that spot and easily capable of burying a person. The Lip and right side of the Bowl represent an isolated area that has the highest frequency of natural avalanches than any other place in the Presidential range, by far. If there is an east facing wind slab avalanche problem and there is an exception to the danger rating, it is highly likely that it will occur in this avalanche path. This avalanche path is steep, leeward and contains multiple terrain features that capture wind driven sluffing snow from the largest fetch zone in the range. These are all reasons that you will never see snow rangers and ski patrollers using unsafe travel techniques on the floor of Tuckerman Ravine. You should consider doing the same, no matter what the danger rating.  

Information on all US avalanche fatalities can be found here with details and accident reports appearing as they are submitted to the CAIC.  An interview with Simon Trautman of the National Avalanche Center on the recent cluster of fatal avalanche accidents can be found here. 

Thanks to everyone for taking the time to submit all the observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming. 

Your avalanche, snowpack, or weather observations are extremely valuable to the forecasters at MWAC. Help create a more accurate avalanche forecast by submitting your observations here. 

Listen to the weekly MWAC Outreach Podcast provided by Ski The Whites. Discussions include snowpack information, weekend outlook, and general avalanche related info.  A very busy vacation week led to Andrew and Frank missing out on this discussion. 

Thursday, February 25 @ 7PM - Barriers to Cognition and Perception with Blake Keogh  - A Free Zoom Webinar.

The Harvard Cabin is open for camping only with no entry allowed inside the cabin. There is no access to the breezeway at HoJos.

Please Remember:

• Safe travel in avalanche terrain requires training and experience. This forecast is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Avalanche danger may change when actual weather differs from the higher summits forecast.

For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.