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Avalanche Forecast

Archived

Apr 6th, 2015–Apr 7th, 2015

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

Regions

Mt Hood.

New snowfall followed by potential sunshine Tuesday could make for rapidly increasing avalanche danger on Mt. Hood, so be aware of quickly changing surface snow instability.   

Detailed Forecast

A slowly changing weather pattern will maintain cool weather, light winds and isolated showers again Tuesday.  Generally light amounts of new snow are expected Monday night through Tuesday.  Avalanche problems Tuesday will revolve around recent storm snow.  

It's April, so be aware of the increased solar input reaching more aspects and affecting the snow surface quickly. Loose wet avalanches involving shallow amounts of recent storm snow will be also be possible Tuesday, especially during sunbreaks in the afternoon.    

Storm slabs may be sensitive Tuesday with new snow bonding poorly to aspects with surface crusts or fail on storm snow instabilities formed during periods of showers. 

Small loose dry avalanches are also possible for non-solar aspects at higher elevations. Loose dry avalanches won't be listed as a highlighted avalanche problem, but be aware of fast moving sluffs knocking you off your feet and into unintended terrain traps on steeper slopes. 

Due to the continued cool weather, cornices won't be listed as an avalanche problem either, but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.

Snowpack Discussion

Periods of active weather and mountain snowfall have finally graced the PNW since about mid March onward. 

A front moved across the Northwest Tuesday, followed by showers and rapid cooling Tuesday night and Wednesday. Storm snow from this system was about 9-15 inches at Mt Hood. The patrol at Meadows on Wednesday reported that the storm snow was surprisingly less reactive than anticipated with few explosive and no ski triggered avalanches observed. 

1-3" of new snow fell at Mt. Hood stations Friday night with some moderate westerly wind transport above treeline, but only very isolated pockets of wind slab up to 1 ft were found above treeline on lee aspects. 

Showers deposited an additional 6-10 inches of new snow as of Monday morning, April 6th. Some local wind transport was noted by patrol at Hood Meadows Monday morning and subsequently some very soft slab conditions noted. 

Snowpack problems at Mt Hood should remain in the upper or surface layers. The mid and lower snowpack at Mt Hood consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this season. Many areas at low elevations do not have enough snow to cause an avalanche danger.

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.

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.