Intermountain

Problèmes avalancheux

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–2

  Rain on snow at lower elevations will create potential for wet loose avalanches in steep terrain. Periods of intense rain overnight on Thompson Pass will make Wet Loose avalanches a possibility in steep terrain below 3000 ft. Take note of how saturated the snow is in the area you travel. Watch for roller balls which are a sign the snow is becoming saturated enough to produce wet loose avalanches.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1.5–2.5

  Warm temperatures and rain up to 3000 ft overnight are forecasted to continue throughout today. With peak intensity forecasted between 11am-3pm. The Layer of Buried Surface Hoar has been stubborn to trigger over the past week, but  warm temperatures and rain  may briefly make this layer that exists below 2700 ft in the intermountain and Continental zone more reactive as the slab consolidates, before likely stabilizing due to the warm temperatures and rain.

  This layer is buried on top of a rain crust which can be easily identified with simple pole probing. If the rain crust exists, so does the buried surface hoar. In the Intermountain zone this layer is buried about 1’ deep and in the continental it is buried slightly less at around 8” deep.  Stay heads up below 3000ft and avoid steep slopes and terrain traps until we can ground truth that the warm temperatures did indeed destroy this layer.

  In the continental zone temperatures stayed below freezing overnight, but storm totals are expected to be less. The buried surface hoar below 3000 ft will likely remain intact for now and new snow throughout the day may increase the sensitivity of this layer.

  This problem does not exist in the Maritime zone anymore due to warm temperatures.

  Storm Slab: Expect new snow to accumulate above 3000'. Pay attention to how much new snow is building and how reactive it feels. Watch for signs of drifting (pillows, textured snow, cracking). Quick assessment tools like hand pits and small test slopes work well for determining how sensitive storm slabs are in the terrain you’re traveling through. The peak precipitation intensity is forecasted for the middle of the day today, so expect sensitivity to increase throughout the day.

  

• 

  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  2–3

  Weak snow near the ground exists at all elevations and is now deeply buried in most locations. In many areas, basal facets are bridged by stronger, stiffer layers in the middle of the snowpack. As this problem gets deeper it becomes harder to trigger and is unlikely to produce obvious red flags like cracking or collapsing. Expect a stubborn, unreactive deep slab in most places—this is a low-likelihood / high-consequence setup.

  The most likely trigger points are thin spots, especially steep, rocky terrain where the weak layers are closer to the surface. A rider may be able to stress the basal weak snow in these shallow areas, and a small trigger could step down or propagate into deeper, thicker parts of the snowpack, producing a large and destructive avalanche. The best way to manage this problem is to avoid steep, rocky features and other shallow-snow areas where the snowpack is thin and variable.

  In the Continental zone, the hazard will remain CONSIDERABLE where the snowpack is thinner, weaker, and more easily affected by human triggers. Human-triggered deep slab avalanches are possible in the Continental zone. They are unlikely in other zones, but if triggered could produce very large avalanches with a very low chance of survival.