Avalanche Forecast

Issued: Mar 18th, 2018 11:00AM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low. Known problems include Loose Wet.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

Cool and spring-like conditions Monday will maintain stable snow in the morning ours. Sunshine and daytime warming will help soften the surface snow making shallow Loose-Wet avalanches possible on some steep sun exposed slopes.  Watch for new roller balls or wet surface snow deeper than your ankle, and avoid travel on those steep slopes.

Summary

Detailed Forecast

Generally safe avalanche conditions exist. Shallow recent snow overlies a strong melt-freeze crust in most areas. Cool temperatures will but increasing sunshine and light winds will counter each other.

Strong sunshine will allow for gradually weakening and melting surface snow on steep sun exposed slopes. Watch for signs of unstable snow, especially sunshine affecting fresh snow, especially in the Timberline area where greater fresh snow has fallen since Saturday. If you encounter rollerballing or natural Loose-Wet avalanches, avoid travel on those steep sun exposed slopes. 

Shallow wind slabs formed Saturday should be mostly stabilized by Monday and have been removed from the problems list. However, watch for any signs of recent wind loading, mainly on N-SE facing slopes, steep convex roll overs, unsupported slopes, or on cross-loaded features above treeline. 

Snowpack Discussion

Showers over the past two days have deposited about 8 inches of recent snow in the Timberline area, with only a few inches of new snow in the Mt Hood Meadows area. The new snow has fallen with cool temperatures and some moderate westerly winds near ridgecrest Friday night.  

Above treeline, shallow and isolated wind slabs have formed early last week. The most recent snow sits atop a melt-freeze crust.

Several melt-freeze cycles last weekend helped to consolidate and strengthen the snowpack. No recent avalanche activity has been reported at Mt. Hood.  

While we are tracking several layers deeper in the snowpack, there are currently no significant layers of concern.

Observations

On Sunday, MHM pro patrol reported no reactivity to any older shallow wind slabs with only very shallow surface snow becoming moist. 

On Friday, Pro-observer Laura Green found 2-4" of new snow near Timberline well bonded to the underlying crust. Poor visibility limited observations above treeline.   

On Wednesday, Mt. Hood Meadows Pro-Patrol reported shallow wind slabs less than 1 ft deep triggered by explosives on N-NE aspects near and above treeline.

 

Problems

Loose Wet

An icon showing Loose Wet

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

Valid until: Mar 19th, 2018 11:00AM