Southeast Mountains

The probability of humans triggering an avalanche is slowly decreasing, while the potential size of an avalanche remains large and potentially deadly. Traveling at upper elevations will still require you to assess and manage for a lingering wind slab avalanche problem. While the most significant avalanche problem to consider is for avalanches breaking up to several feet deep on persistent weak layers existing around much of the compass. Early warning signs such as shooting cracks or a collapsing snowpack have become rare, and may not exist before an avalanche releases. Consider what a large avalanche would look like in the terrain you are riding. Areas where an avalanche would push you into a terrain trap or into trees, for example, will increase the consequence of a triggered avalanche. 

Clear weather yesterday allowed us to document more avalanche activity. Some avalanches may have released as recently as yesterday, like this avalanche on a cross-loaded terrain feature in Red Lady Glades. While the majority of recent avalanches occurred last Wednesday and Thursday. Some of those avalanches have only involved the recently wind-blown snow, while many others have stepped down into deeper weak layers, propagating wider and becoming large in size. Head on over to the avalanche observations tab, and take note of the size, and locations of those recent avalanches. 

Be mindful of your terrain selection heading into a gorgeous weekend. The forecast team still feels uneasy about the current snowpack. A notable natural avalanche cycle occurred as recently as Wednesday and Thursday. We can expect more avalanche activity to get documented this weekend. Snowpack observations assessing the likelihood of triggering a persistent slab avalanche are difficult and will produce variable results. The distribution of problematic weak layers has also become variable through the terrain. The easiest assessment right now is assessing the consequences of the terrain you are riding. If you are riding avalanche terrain, look for ways to reduce the consequences of getting caught in an avalanche. Such as avoiding areas where an avalanche could pull out a large terrain feature, pile deeply into a terrain trap, or slam into trees. 

Below a a copy of the forecast discussion from Friday 2/23:

Northwest Mountains:  Up to a foot of recent snowfall was blown by westerly winds over several days.  Poor visibility on Thursday thwarted views into the range and left some uncertainty about the extent of recent natural avalanche activity.  One observer noted a large recent avalanche in Yogi's on Schuylkill Ridge (northeast-facing, near treeline) that may have failed a few feet deep.  This serves as a good reminder that the surface hoar layer buried in early February remains problematic, particularly for terrain with recent drifting.  Remain suspicious if you plan to travel through terrain highlighted by the Persistent Slab rose; signs of instability have been relatively infrequent and may not warn you before releasing a dangerous avalanche.  Multiple tracks could be on the slope before someone finds the right spot to impact the weak layer.  You can always select low-angled slopes to manage the risk, but if you choose to ride steeper terrain, it would be wise to select terrain with less severe consequences.  Cautiously approach steep terrain with a keen eye for the consequences as a triggered avalanche on the surface hoar layer will be large and dangerous.  Persistent weak layers like surface hoar often surprise skilled professionals.

Southeast Mountains:  Avalanche conditions continue to hover near a dangerous level around the Southeast Mountains.  Generally, slabs above the early February weak layer (and basal weak layers) are thinner and more prone to human triggering.  Recent wind drifting makes it more likely for you to trigger an avalanche deeper in the snowpack.  A second-hand observation from upper Cement Creek, suggested deep failing avalanches near Hunter Hill and Crystal Peak in the past few days (forecasters plan to travel through this area today to get more details).  Avoiding terrain with recent drifting is a straightforward choice today.  In sheltered areas, the slab above the February surface hoar layer is 1 to 2 feet thick which leaves it squarely within the depth for human-triggers.  One observation from below treeline in the Southeast Mountains suggested a decreasing sensitivity to human triggers with moderate results in an Extended Column Test.  This merely suggests an incremental improvement in avalanche conditions; we are far from being out of the woods, particularly in the Southeast Mountains where slabs are thin.  Carefully manage slope angles in sheltered terrain highlighted by the Persistent Slab rose to reduce the risk of avalanche.