Avalanche Forecast
Issued: Feb 12th, 2017 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet.
NWAC,
Northwest Avalanche Center
Watch for melting and weakening surface snow on steep sun exposed slopes where loose wet avalanches will be possible. Continue to be cautious in steep previously wind loaded terrain or any features showing signs of wind deposited snow.
Caution travelling on steep slopes with a slick crust.
Summary
Detailed Forecast
Sunshine and very mild temperatures with light to moderate ridgetop winds are expected Monday. Freezing levels should near 10,000 feet by later Monday.
Older wind slabs should have settled and stabilized by Monday, but watch for signs of wind deposited snow on specific terrain features such as steep slopes below ridges.
Sunshine and very mild temperatures Monday should make loose-wet avalanches possible on steep southerly slopes facing the sun. Be cautious on sun exposed slopes if the wet surface snow becomes more than a few inches.
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 of consequence.
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.
Things changed in a hurry as strong SSW flow brought a series of storms with heavy rain to above treeline in the west slopes of the Cascades (Mt. Baker, Crystal and Paradise) Wednesday afternoon and Thursday. A mix of snow, sleet, freezing rain, and rain fell in the Cascade Passes during these storms leading to extended pass closures.
A switch to westerly flow brought a rise in temperatures in the Cascade Passes Thursday afternoon and night.
Friday was windy with a slow cooling trend during the day. Light showers increased and generally became moderate in the afternoon before tapering Friday night.
Most areas along the west slopes of the Cascades received about 6-8 inches of new snow, while the Baker area received about 14 inches by Saturday morning.
The aftermath of this storm cycle left a very strong rain crust with whatever amount of new snow received above, following the rain changing to snow. This ranges from 6-16 inches, except for areas exposed to some strong westerly winds striping new to and exposing a firm and slick crust.
High pressure Saturday and Sunday brought increasing sunshine and warming temperatures, allowing for several inches of snowpack settlement, allowing for a decreasing danger..
Recent Observations
North
Mt. Baker pro-patrol reported that the cooling trend had quickly locked up the recent wet snow within the ski area by Friday morning. Strong W-SW winds were transporting snow to lee slopes and not bonding well to the new crust.
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 more likely 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.
South
Crystal pro-patrol observed several loose wet slides up to size D2, all aspects, within the ski area Thursday. No large slab releases were produced with explosives, Thursday afternoon. Wet slabs estimated to be about 1 ft deep were observed from the ski area in Pickhandle Basin.
White Pass reported similar conditions as the other Passes, with a freezing rain crust up to at least mid-mountain and very strong W-SW winds atop Pigtail Peak through Friday.
Problems
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
Expected Size
Valid until: Feb 13th, 2017 10:00AM
