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Avalanche Forecast

Archived

Dec 23rd, 2014–Dec 24th, 2014

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.

The main avalanche problems Wednesday should be new wind slab and new storm slab.

Detailed Forecast

A change to northwest winds, decreasing snow showers and much lower snow levels will be seen at Mt Hood Wednesday afternoon. About 6-12 inches of new snow seems likely mainly in the near and above treeline by Wednesday midday.

The main avalanche problems at Mt Hood Wednesday should be new wind slab and new storm slab. These new layers should be found mainly in the near and above treeline. Avoid travel on steep lee slopes with firmer wind transported snow that is a sign of wind slab. Storm slab should be limited to steep slopes in areas that receive more than an inch of snow an hour for at least several hours.

Have a plan in place before you get to the trailhead. Confidence is fair for this forecast.

Snowpack Discussion

A strong warm storm moved over the Northwest Saturday and Sunday. Especially strong winds and heavy precipitation was seen at Mt Hood. Little in the way of observations is available for the weekend for Mt Hood except for an observation via the NWAC Recent Observations for Timberline for 20 December.

Decreasing winds, a little cooling and about 5-10 inches of new snow was seen at the tail end of the storm at Mt Hood Sunday night. A relative break and some stabilizing was generally seen Monday.

The Mt Hood Meadows ski patrol reports a 1-2 cm surface crust and surface snow becoming saturated due to rain on Tuesday. Debris from natural avalanches over the weekend was seen in Heather Canyon.

A moist cold front is moving over the Northwest Tuesday to Wednesday morning. This will be accompanied by strong southwest winds, moderate to heavy rain changing to snow, and lowering snow levels.

 

 

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.