Avalanche Forecast

Issued: Feb 13th, 2017 10:02AM

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

Northwest Avalanche Center NWAC, Northwest Avalanche Center

Tuesday should be a mostly safe avalanche day in the Olympics and Cascades. Watch for signs of loose wet snow steep sun exposed slopes. Use caution travelling on steep slopes with a slick surface crust.

Summary

Detailed Forecast

Tuesday morning should start out mostly sunny but increasing clouds will be seen by Tuesday afternoon especially in the Olympics and northwest Cascades. Alpine winds will increase with high freezing levels and mild temperatures but with cooler east winds in the Cascade Passes. Significant rain or snow should hold off until Tuesday night and Wednesday.

Some initial sunshine and another day of mild temperatures Tuesday should make loose wet avalanches possible on steep slopes facing the sun. Be cautious on sun exposed slopes if the wet surface snow becomes deeper than a few inches.

Older wind slabs should have mostly settled and stabilized the past couple days. Significant new wind slab is not expected Tuesday as southeast to southwest winds won't transport sun affected snow. But continue to watch for signs of wind deposited snow on north facing terrain features.

Some slopes exposed to recent winds or where less new snow was received after rain changed to snow may have an exposed very slick crust. Be cautious of uncontrolled falls and avoid traveling on steep slopes with slick crust in terrain where an uncontrolled fall could have serious consequences.

Snowpack Discussion

Weather and Snowpack

A strong storm cycle Friday, 2/3 through Monday 2/6 deposited 3-5 feet of snow along the west slopes of the Cascades. 

Strong SSW flow carried a frontal system with deep moisture across the Northwest on Wednesday 2/8 and Thursday 2/9. This caused rain to high elevations and a loose wet and wet slab avalanche cycle along the Cascade west slopes. A mix of snow, sleet, freezing rain and rain fell in the Cascade Passes leading to extended pass closures.

A cooling trend followed on Friday with NWAC sites along the Cascade west slopes receiving about 6-8 inches of new snow by Saturday morning with Mt Baker getting about 14 inches.

The aftermath of this storm cycle left a very strong rain crust with whatever amount of new snow received above, except for areas exposed to west winds which remained scoured to the firm and slick crust.  

High pressure Saturday to Monday brought increasing sunshine and warming temperatures. Temperatures reached the 40's and 50's in many areas of the Olympics and Cascades on Monday. This has brought snowpack settlement, some small loose wet avalanche activity and a decreasing avalanche danger.

Recent Observations

North

NWAC pro-observer Lee Lazzara was in the Mt Baker backcountry Saturday and reported a favorable increasing resistance profile in the storm snow over the very strong rain crust. Observations were not made in terrain where wind slabs may have formed. 

Central

NWAC observer Dallas Glass was at Paradise Sunday and confirmed the recent wind and storm slabs have settled and stabilized. By Sunday afternoon, strong sunshine and temperatures into the mid 40's triggered numerous rollerballs from many steep sun exposed terrain features, especially rock features. There was evidence of numerous wet slab avalanches that released several days ago during the heavy rain event with average crown depths around 2 feet. The underlying rain crust is now very hard and supportive, with an average of about 10 inches of recent snow over the crust in wind sheltered terrain.

A report via the NWAC Observations page indicated many small loose wet avalanches on the south side of Mt Lichtenberg on Sunday.

The Stevens Pass pro-patrol reported no avalanche activity on Monday.

South

The Crystal Mountain pro-patrol on Monday reported some rollerballs on solar slopes at lower elevations with wind cooling the ridges.

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: South East, South, South West.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Feb 14th, 2017 10:02AM