Mt Hood

Expect conditions to change during the day Wednesday as the snowpack transitions from a cold storm to warmer temperatures and sunshine. Fresh wind slabs will be reactive to human triggering, so keep your eyes open for places where the wind drifted the snow into deeper slabs, and avoid wind loaded slopes greater than 35 degrees. As the sun comes out, expect natural loose avalanches from steep sun-exposed slopes. Don’t get surprised by these easy to predict and avoid avalanches,  and don’t linger under sunny slopes where natural avalanches may occur.

Wednesday will be a day of transition for the snowpack in the Mt Hood area. As snow showers end, temperatures rise, and the sun comes out, the snowpack will change quickly. Be prepared to adapt to these changes during your day. Slopes you travel in the morning may be very different later in the day.

This storm hit the Mt Hood area the hardest with the strongest winds and significant new snow. Storm slab conditions may linger in areas Wednesday. Be suspect of any location that received more than 10 inches of new snow. In these areas, you may find conditions different that the avalanche forecast implies.

This new snow may have buried a variety of surfaces, including firm crusts, wind pack snow, facets, and areas of surface hoar, all reported in the Mt Hood area. This is in addition to a layer of buried surface hoar and/or facets from earlier this month. How will these layers fair under the new snow load? It’s tough to say. These weak older layers were less prevalent in the Mt Hood area than adjacent zones to the north but where present, there is the potential for larger avalanches to fail in unusual ways. The only way to observe these layers is to dig in the snow. If you take the time to look at these layers, keep your eye out for sugary facets or feathery surface hoar buried 1 and 2 feet below the snow surface.

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. 

Moving Forward

As we move further into March, there are two points to consider:

• 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.

• 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.