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Avalanche Forecast

Archived

Dec 23rd, 2018–Dec 24th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

Dangerous avalanche conditions will remain on Monday as 1-2’ of snowfall from the past 48 hours requires time to stabilize. Winds have created the potential for very large avalanches which you can still trigger.

Discussion

Snow and Avalanche Discussion

Thursday's storm system brought warmth and moderate to strong W-SW winds during the day, followed by a few inches of snow and more wind Thursday night.  A strengthening rain crust should be easily discernible near and below treeline, with just a few inches of recent snow sitting on top in wind sheltered areas.

Weak snow formed and buried earlier in the month was identified in the upper snowpack as recently as December 17th. Mt. Hood Meadows pro-patrol found buried surface hoar mostly intact in sheltered locations from 5500 to 6500 ft. We continue to seek more information about this layer and are concerned that the large loading event may cause some slides to release on or step down to this layer at higher elevations.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.