Avalanche Forecast

High pressure should cause a clear, cold night Wednesday and a sunny day Thursday with light winds and cold temperatures. There has been low density snow available for recent transport and with the expected cold temperatures, wind slabs will be slow to settle and stabilize. 

The fresh wind slabs should be primarily on lee South-West-North aspects. However, also watch for cross-loaded slopes and lingering wind slab on a variety of aspects. Watch for firmer wind transported snow and avoid freshly loaded slopes in all elevation bands.

The wind slab problem compass indicator below shows loading for the recent dominant wind direction, but other areas, such as Mt Baker may have experienced other loading pattern, so be alert in all terrain for wind deposited snow.    

Small loose dry avalanches are possible in steep wind sheltered terrain, but will not be listed as an avalanche problem. 

Weather and Snowpack

A cold and dry Arctic air mass was over the Northwest last week. The main weather event during this cold snap was a day of strong east winds last Wednesday that created widespread variable snow surfaces by scouring windward slopes and re-distributing the snow to a variety of aspects.

Reports indicate the winds eliminated most of the faceted surface snow and surface hoar that formed in the near and above treeline during the cold weather. But these weak surface crystals were still reported below treeline prior to snowfall that fell over the weekend.

A pair of warm fronts moving through the PNW Sunday and again Sunday night left temperatures see-sawing near or above freezing for areas away from the Passes with milder Pacific air finally dislodging colder air in the Passes late Sunday night. 5-10 inches of snow fell through Monday morning with snow showers depositing another 5 inches in the Mt. Baker area through Monday afternoon.

A low pressure system, tracking across southern Washington Tuesday morning through Wednesday afternoon, deposited another 3-6 inches of snow with light winds from Stevens Pass and southward, with Paradise adding another 12 inches. A period of strong East or Northeast winds increased Tuesday afternoon through early Wednesday before diminishing Wednesday afternoon. 

Recent Observations

Wind slabs were touchy last week during the height of the east wind event with two serious skier triggered hard wind slabs reported in the Crystal backcountry on Wednesday. The larger wind slab avalanche resulted in the 2nd avalanche fatality of the season in Washington. See the excerpt above for more details. 

NWAC pro-observer Lee Lazzara was out in the Glacier Creek drainage west of Mt Baker on Saturday and noted surface hoar below treeline in wind sheltered locations. Alpental pro-patrol noted a similar setup of surface hoar below treeline. 

Mt. Baker pro-patrol checked in on Monday, not only with the most snow from the latest storm, but also with the most sensitive storm slab both in the area and out. 12-14" inch storm slabs released easily and on most aspects in area during control work Monday morning. A natural avalanche cycle that likely occurred Sunday night produced widespread 12-18" slabs off the Shuskan Arm. 

On Tuesday, pro-patrol at Alpental found sensitive and widespread, but shallow storm slabs of 3-4". There was no indication of slabs releasing to deeper layers in their area. 

NWAC observer Dallas Glass was in the Kendall Peak area below treeline Tuesday. Dallas found the new snow generally right side-up with good snow conditions. A freezing rain or rain crust was ski supportable and down 25 cm. The crust disappeared above 4800 feet. The only direct signs of instability noted, were small loose dry sluffs on steeper slopes. Via the highway, strong east wind was beginning to transport snow on Granite Mountain by mid-afternoon. 

A report on NWAC observations page Wednesday 1/11, indicated reactive wind slabs near treeline in the Snoqualmie Zone, with a touchy ski triggered wind slab releasing on wind loaded northerly aspect.

NWAC observers Dallas and Ian were back in the Crystal backcountry Wednesday, 1/11 to assess the distribution and sensitivity of fresh wind slabs from recent strong E-NE winds.  The report is the wind slabs are present and become bigger, wider and generally more scary as you move into the near tree line band and exposed ridges. NE-E-SE facing slopes were stripped of recent snow with new reactive wind slabs on S-W-N facing terrain and cross loaded features. Travel in this area was therefore conservative. In wind sheltered terrain below treeline, the storm snow was right side up and lacked any slab structure with excellent skiing conditions. The fresh wind slab was the primary problem with no older layers considered relevant in this zone. Loose-dry avalanches were suspect on steep sheltered slopes, especially with the cold temperatures limiting any settlement or bonding.