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Avalanche Forecast

Archived

Feb 11th, 2015–Feb 12th, 2015

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

Regions

Mt Hood.

Although less likely, the primary avalanche problems Thursday will continue to be loose wet avalanches near and above treeline and lingering wind slab on lee aspects above treeline.

Detailed Forecast

Mild freezing levels will prevail again on Thursday with high overcast and occasional sunbreaks forecast. 

Loose wet avalanches are possible Thursday on steeper solar slopes near and above treeline that receive substantial sun breaks.    

Lingering wind slab will be listed as a problem for one more day above treeline. Watch for firmer wind transported snow on previous lee slopes, mainly on N-SE slopes near ridges.

As a result of the overall low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation.

Snowpack Discussion

The latest atmospheric river to impact the Pacific Northwest brought less rain to Mt. Hood versus areas further north late last week. This event led to overall snowpack settlement, and at lower elevations, continued melting of the seasonal snowpack.   

The last frontal system crossed the south Cascades late Monday. This caused strong winds and heavy snow in the above treeline zone at Mt Hood.

On Tuesday, the Meadow pro-patrol reported 15 inches of new snow at 6600 feet. Avalanche control gave numerous size 1-2 wind and storm slab avalanches on lee slopes but with limited propagation. Similar wind slab concerns were reported on lee east aspects west of Timberline Tuesday on the NWAC observation page.  

On Wednesday, Mt. Hood Meadows pro-patrol reported high overcast had limited the loose wet potential on an otherwise mild winter's day, and no new avalanches were observed. 

The mid and lower snowpack at Mt Hood should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.