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Avalanche Forecast

Archived

Jan 14th, 2014–Jan 15th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Tonight and Wednesday:  The cold front move SE of the region tonight. Precipitation will ease, extreme winds should remain strong from the NW, freezing levels lower to around 600 m by tomorrow morning. Thursday: A ridge of high pressure is well in place. Continuing rising freezing levels climbing to 1700 m on Friday. Strong SW winds are forecasted. Friday overlook: Ridge is still dominating the pattern with clear skies and warm temperatures.

Avalanche Summary

An avalanche cycle is most likely occurring with the present stormy conditions. Yesterday, a natural avalanche size 3.5 was reported SE outside of the region. Explosives also produced up to size 2.5 avalanches in the storm snow yesterday in the NW Coastal region.

Snowpack Summary

60-100 cm of storm snow will have fallen above 1500 m. elevation with extreme W winds. Wet and saturated snowpack under this elevation should start receiving solid precipitation tonight as freezing levels drop. Thick touchy windslabs will keep developping lee of strong NW winds in the alpine and at treeline tomorrow keeping avalanche conditions very dangerous. At lower elevations, a layer of dry snow will cover a very wet snowpack which will could still be susceptible for wet slab avalanches or loose wet avalanches. This instability should not remain for very long since the lowering freezing levels will help stiffening up this wet layer.  Under the storm snow, the early January surface hoar layer or facet/crust combo is found in sheltered areas and is still a concern to avalanche professionals. Below this the mid and lower snowpack is gaining strength. The exception is where a layer of weak snow is lingering just above the ground in the shallower snowpack found in the North of the region.

Problems

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.

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.