Avalanche Forecast
Regions: Mt Hood.
Loose avalanches, generally small, may release naturally or be human triggered as the sun comes out again Monday. Take care around terrain traps that would amplify the consequences of a small avalanche.
Discussion
Snow and Avalanche Discussion
Sunshine, cool temperatures and a stiff easterly breeze kept loose avalanches from becoming large Sunday. Monday will be milder and sunny, but last week's snowfall will have had another day to settle. Look for avalanche conditions to worsen Monday night and Tuesday as a new round of snow and wind impacts the Mt. Hood area. Â
Natural wind slab avalanches that released Friday or early Saturday were observed in White River Canyon on east aspects above treeline, estimated to be 1-2' deep. No new slab avalanches were observed over the latter half of the weekend.Â
Snowpack Discussion
March 10, 2019
February started stormy and cold with very active avalanche conditions on persistent weak layers. The month finished with continued cold temperatures but drier weather allowed avalanche activity to taper off. Persistent weak layers that were buried early in the month (Feb 8th) are now unreactive, though you can still find the grains.
Aside from the series of storms in early to mid-February, most regions have measured relatively light snow accumulation in the past 3 weeks. Snow has stayed soft especially on shaded slopes and faceting and surface hoar have been plentiful. While there has been plenty of sunshine since mid-February, very cold temperatures have kept melt-freeze crust to a minimum on sunny slopes.
A natural loose wet avalanche (D1.5) on a southeast aspect of Lichtenberg Mtn at 5,400ft. 3/10/2019. Photo: Josh Hirshberg
Recent Avalanches
Our attention shifted to the upper snowpack. Recent avalanche problems have largely focussed on wind transported snow and weak snow surfaces on both dry, shaded slopes and sun-exposed aspects. In some locations, a weak layer of surface hoar and facets was buried on March 6th. We’ll keep an eye on this interface as we move into the future.
A skier-triggered storm slab avalanche (D1.5) on Shuksan Arm, north aspect, 5200ft. 03/09/19 Adam U Photo.Â
Moving Forward
As we move further into March, there are two points to consider:
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The strength of the March sun: As the sun creeps higher into the sky and the days grow longer, the sun can have a greater impact on the snow surface. When the sun comes out, expect things to change quickly. You may see avalanches conditions change with natural loose avalanches originating from sunny slopes, surface snow becoming thick and heavy, and slabs taking on a moist to wet snow character.
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Weak surfaces: facets and surface hoar have blanketed snow surfaces in many zones. Any significant snowfall will bury well-developed and widespread persistent weak layers. Recently, most storms have not delivered enough precipitation to cause a problem.
Avalanche Problems
Loose Wet
With sunny skies and milder temperatures forecast Monday, loose wet avalanches are most likely to release from steep, rocky, sunny slopes as the day progresses. Monitor changes in the upper snowpack, looking for natural pinwheels or small loose wet avalanches as clear signs of increasing danger. Avoid terrain traps like gullies where even a small avalanche can bury you.
In the same vein, on very steep shaded slopes loose dry avalanches continue to have the potential to run fast and far.
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1