Regions
Northwest Inland.
Big winds and a bit of snow are forecast through the weekend. Give the immature snowpack room to breathe by choosing conservative terrain.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Synopsis: Warm air riding up and over the arctic air has created an above freezing layer at upper elevations that should stick around through Thursday afternoon. The dregs of a storm system move inland Thursday night. Snow totals are respectable, but nothing special.Thursday: Freezing Level: Valley Bottom, Above Freezing Layer 1200m to 2000m Precipitation: 1 to 5mm | 1 to 5cm; Wind: Treeline: Moderate SW | Ridgetop: Strong, W.Thursday Night: Precipitation: 3 to 6mm | 3 to 10cm.Friday: Freezing Level: 800m; Precipitation: 1 to 3mm | 1 to 5cm; Wind: Treeline: Strong, W | Ridgetop: Extreme, NW.Saturday: Freezing Level: Valley Bottom; Precipitation: Trace; Wind: Treeline: Light, Variable | Ridgetop: Moderate, W.
Avalanche Summary
No new avalanche activity to report from this region. In the neighboring NW Coastal region on Tuesday wind and storm slabs to size 2.5 ran on NW, SW and SE facing aspects between 1500 and 2000m.On Dec 29 a rider triggered a size 1.5 avalanche on a north aspect in the alpine at 1700m. The small steep wind loaded slope was triggered when the machine was climbing, the rider reportedly rode out of the avalanche behind the debris. See the Mountain Information Network for a photo and more details.
Snowpack Summary
Total snowpack depth is around 80 to 90cm.Strong outflow winds on Dec. 29 left a variety of wind affected conditions in their wake in wind exposed terrain at all elevations. Some windward aspects and ridgelines were scoured down to bare ground. North facing slopes that still have snow are likely wind pressed. The thickest and likely hardest slabs should be found on south facing features and some degree of crossloading is likely found everywhere else.A layer of buried surface hoar down about 30-50 cm appears to be spotty in distribution, but is still a concern.Something of a sleeping giant can be found down near the bottom of the snowpack where a crust facet combo that was formed in mid-November lies dormant. This layer is producing variable results in test profiles, some sudden, some not. I suspect it will remain sensitive to new inputs in the form of new snow and wind for the foreseeable future.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.