Continental

Lawinenprobleme

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–1.5

  Wet loose activity became a concern this week as recent snowfall was rapidly warmed by the strong April sun and numerous small to large avalanches occurred. Today, activity is expected to remain limited and mostly confined to lower elevations, as cloud cover should reduce solar input and melt-freeze crusts above 2000' are not expected to break down.

  Wet loose activity is expected to increase again in the coming days once the sun returns and begins heating any new snow that falls with the current low pressure system. Watch for signs of instability such as rollerballs and moist to wet snow deeper than a few inches. The most affected slopes will change throughout the day as the sun moves across the sky. Steep rocky terrain is often the first to become active during periods of strong sun, as rocks warm quickly and transfer heat to the surrounding snow. Keep wet loose avalanches in mind when planning your route.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1.5–3

  Persistent Slab: Over the last week, 4–10 inches of snow accumulated above 1000', followed by strong sun and increasing temperatures. This was the first moderate stress the snowpack had seen in quite some time, and sensitivity increased immediately, with numerous skier-triggered avalanches reported and observed on 4/9. Users should take those observations as a clear sign that our snowpack remains weak and that even modest additional stress can quickly increase snowpack sensitivity.

  The chances of triggering an avalanche are lower today as the snowpack has had time to adjust to the new load and cloud cover will limit the sun’s effect on snow surfaces. Light snowfall today is not expected to significantly increase the hazard. Even so, it will still be possible to trigger an avalanche 1–3 feet deep where stiffer slabs overlie faceted snow. This problem is difficult to identify due to the high degree of spatial variability in our snowpack. Digging or probing for stiffer snow over weaker faceted snow can help identify areas of concern.  Choosing simple terrain, avoiding steep rocky slopes where facets are likely to exist, and limiting exposure to terrain traps remain the best ways to reduce risk today.

  Deep Persistent Slab: Weak snow buried over a meter deep becomes more widespread as you move north through our forecast zones, with the Continental zone remaining the most concerning. Although it is still unlikely to trigger this layer, slopes that have been scoured by strong northeast winds now have a shallower snowpack, bringing this weak layer closer to the surface and making it easier to affect in isolated areas.

  This remains a low-likelihood, high-consequence problem that may become more concerning as warming temperatures penetrate deeper into our weak snowpack in the coming days. Probing for a shallower snowpack and strong snow over weaker layers below can help identify areas where this problem may be more likely.