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Avalanche Forecast

Archived

Apr 5th, 2015–Apr 6th, 2015

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

Regions

Mt Hood.

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

Detailed Forecast

An upper level weather disturbance should bring light to moderate snow to Mt. Hood Sunday evening through Monday morning followed by decreasing showers and potential mid-day sunshine. Avalanche problems on Monday will revolve around storm snow received Sunday evening through early Monday.  

It's April, so be aware of increased solar input reaching more aspects and affecting the snow surface more quickly than winter-time. Loose wet avalanches involving recent storm snow will be likely Monday if there are sunny periods in the late morning or early afternoon.   

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

Small loose dry avalanches are also possible on non-solar aspects at higher elevations. Loose dry avalanches won't be listed as a top 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. 

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.