Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 26th, 2015–Dec 27th, 2015

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

.

Lingering storm and wind slabs instabilities will continue to settle on Sunday. Watch for sensitive wind-loaded slopes especially near and above treeline, and stick near your partner to help mitigate the deadly risk of deep snow immersion below treeline.  

Detailed Forecast

A frontal system on Sunday should drop a few inches of new snow with light to moderate southerly transport winds. This system will stack up short compared to some of the burly snow totals received over the last week. 

However, recent cool temperatures should continue to slow the otherwise stabilizing trend in the upper snowpack. The danger will remain elevated in the above treeline zone where larger avalanches are possible on specific wind-loaded slopes.  

Recent wind slab will be most likely to linger on north to east slopes in the near and above tree line. Wind and storm slab avalanches should stay within recent storm layers but could still move fast. Test for inverted strong over weak storm snow and give cornices a wide margin.

Beware of loose dry avalanches in steep non-wind affected terrain that could have unintended consequences such as knocking you off your feet and into a terrain trap.

Remember to discuss plans and maintain visual contact with your partners. Recent unconsolidated storm snow is very deep in many places with possible very large tree wells. There have been snow immersion fatalities in tree wells already this season at Snoqualmie and in Canada.

Snowpack Discussion

We have had about a week of heavy snow and cool temperatures in the Olympics and Cascades. Sites near and west of the crest have had 5-9 FEET of snowfall through the morning of the 24th, with only light additional accumulations since then. There has been slow settlement over the last few days, but the main message is that it is still deep out there!  

The most recent avalanche observations include shallow storm slab releases from Alpental pro-patrol during AM control work on Christmas and of a small skier triggered storm slab near treeline in the Crystal backcountry Saturday, underscoring that storm snow instabilities remain days after the heaviest snowfall ended.   

Older observations

NWAC pro observer Lee Lazzara was in the Canyon Creek area near Mt Baker on Wednesday in the 2000-5400 foot range and found a right side up upper snow pack but with new snow layers also building quickly and a weaker storm layer at 20 cm. He noted numerous small natural and triggered storm slab and loose dry avalanches mainly on west to north to east facing slopes.

The Baker pro patrol on found fairly extensive 6-8 inch storm slab on Thursday morning. A skier out of bounds on a northwest slope at 4500 feet also triggered a 6-8 inch storm slab and was buried except for a glove showing and was luckily dug out by his friends.

NWAC pro observer Dallas Glass was at East Peak near Crystal Mountain on Thursday and found an overall right side up snow pack. The low sun angle was causing little solar effects on the snow. Storm layers at about 30 and 45 cm were not significantly reactive with minimal propagation. He reported one small natural 12 inch storm slab on an east slope at 5800 feet that had released similarly on each of the previous couple days along with several small loose dry avalanches. He kicked a couple cornices onto test slopes without results.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.