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Avalanche Forecast

Archived

Jan 25th, 2018–Jan 26th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

Dangerous avalanche conditions will persist Thursday, especially in terrain receiving wind transported snow. Avoid steep open slopes. Give safe margins near and below growing cornices. Storm snow is very deep! Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times. Storm layers will take extra time to stabilize.

Detailed Forecast

Moderate rain and snow late Wednesday should taper to light to moderate showers with a cooling trend overnight Wednesday and Thursday.  

Increasing crest level winds are expected Wednesday night and Thursday. 

The avalanche danger will lower slightly Thursday, but it will take time for these deep storm slab layers to stabilize, mainly at lower elevations with little wind exposure. Near and above treeline, strong winds should continue to build wind slabs along lee slopes below ridges and exposed open terrain.

Dangerous avalanche conditions will persist due to the likelihood for triggering a large and potentially deadly avalanche. Recent storm and wind slabs will require time to heal, so be patient and match your terrain selection appropriately, namely very conservative.

Significantly transformed snow conditions have taken place during this extended storm cycle. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.

Snowpack Discussion

An extended storm cycle continues. Over the past 6 days, 3+ ft of storm snow has fallen over a strong rain crust buried 1/18. 

Warming early Wednesday, along with heavy snowfall and strong winds led to increased sensitive avalanches, mainly in terrain exposed to wind affected snow. Slab avalanches of 1-2 ft were common.

Dense storm slabs built quickly early Wednesday, forming over weaker storm snow. 

Poor visibility and frequent storm conditions have limited observations above treeline recently, where a high degree of uncertainty exists regarding the extent and sensitivity of wind slabs above treeline.

Observations

On Wednesday, there was an avalanche accident involving a professional avalanche worker. A wind slab of 2-3 ft was triggered and the individual was caught, carried and partially buried. Rescue was quick and the victim was responsive and transported to hospital for evaluations. Hoping for a good outcome. More information will be forthcoming.

On Tuesday Mt. Hood Meadows Pro Patrol reported rain to 3800'. Wind slabs were building near and above treeline on top of lower-density snow received over the weekend. The slabs were sensitive to skier triggering down to the crusts from 1/16 or within the storm snow. Slab depth was variable. Winds were moderate near and below treeline and strong above treeline.

On Monday morning, Mt Hood Meadows Pro Patrol reported 6" of new snow at 5300' and 13" at the top of their terrain that fell on Sunday night. Wind slabs up to 1' were found into near treeline terrain, with the larger releases triggered by explosives.

Problems

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.

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.