Avalanche Forecast

Archived

Apr 2nd, 2018–Apr 3rd, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

Be patient Tuesday and allow recently formed wind and storm slab avalanches time to gain strength. Use visual clues such as snow drifts, fresh cornices, and uneven snow surfaces to identify and avoid steep wind loaded slopes near ridgeline and on cross-loaded features. You are most likely to trigger lingering storm slabs near convex rollovers, on unsupported slopes, or in terrain greater than 40 degrees. Conditions can change quickly when the sun comes out. Be ready to adjust where and how you travel as snow surface conditions change Tuesday.

Detailed Forecast

Avalanche hazard will decrease slightly Tuesday as a break in the weather allows recently formed wind and storm slabs time to gain strength.

You will still be able to trigger wind slabs on lee aspects near ridgelines and mid-slope cross-loaded features. You can use visual clues such as uneven snow surfaces, snow drifts, and cornices to identify and avoid steep wind loaded slopes. Firm wind slabs are difficult to predict and may break well above you. If you suspect a steep slope is wind loaded, stay off of it and allow it time to gain strength.

Storm slabs will slowly gain strength Tuesday becoming harder to trigger. You are most likely to trigger a storm slab near convex rollovers, on unsupported slopes, or in very steep terrain. Avoid these types of features until storm slabs have time to heal.

Expect new rollerballs, pinwheels, and small loose wet avalanches to occur during periods of prolonged sunshine. The April sun is very strong and snow conditions can change quickly. Be cautious on steep slopes where the consequences of even a small loose wet avalanche can be high.

Snowpack Discussion

In general 12-14” (30-35cm) of new snow fell in the Mt Hood area Sunday and Monday. Strong westerly winds during the storm redistributed snow at higher elevations likely forming wind slabs on lee slopes. The new snow fell on a firm melt-freeze crust in many locations forming an initially poor bond.

There are currently no significant layers of concern in the mid or lower snowpack.

Observations

On Monday, Mt Hood Meadows ski patrol reported 1-2 ft (30-60cm) Wind Slab avalanches on lee slopes above treeline during control work. Near treeline, 6-12 inch (15-30cm) Wind Slabs were triggered on wind loaded slopes. Below treeline the 12-14 inches (30-35cm) of recent storm snow lacked slab properties, however Dry Loose avalanches were possible.

On Saturday, Mt. Hood Meadows pro-patrol reported high overcast skies limiting the softening of surface snow on all aspects. No new avalanches were observed.

Problems

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.

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.