Avalanche Forecast
Regions: Olympics.
Recently formed wind slabs may be found on lee aspects near and above treeline. Expect extreme variation in snow depths in the Hurricane Ridge area due to recent stormy conditions. We have no recent snowpack observations from this area, so take the time to properly assess conditions before engaging in avalanche terrain.
Discussion
Discussion
Heading into the weekend, we are exiting a stormy week at Hurricane Ridge that featured fluctuating snow levels and long stretches of high winds. A wet snowpack began to refreeze Thursday night, a trend that will continue through Saturday. Expect extreme variation in snow depths in the Hurricane Ridge area due to recent stormy conditions. The below treeline snowpack is likely still marginally thin to support avalanches below 4500-5000'. We have not had any snowpack observations since last Sunday, and even those were limited due to widespread power outages and road closures at the Park. Keep this in mind and buffer in the extra uncertainty while making terrain selections.
Forecast schedule
For the 2018-19 winter season, avalanche hazard ratings will be issued for the Olympics Friday through Sunday and during holidays.
On days that the Hurricane Ridge road is closed, No Rating will be applied. We will continue to provide general snowpack and weather summaries for the Hurricane Ridge area even when No Rating is issued.
Snowpack Discussion
Regional Synopsis: December 19, 2018
Why has the avalanche danger been so high for so long? Two reasons: A very active and wet weather pattern combined with a widespread persistent weak layer.
For perspective, the approximate snow totals from 12/9-12/19 are:
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Mt Baker: 102â€
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Washington Pass: 55â€
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Stevens Pass: 76†mid-mountain
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Snoqualmie Pass: 68†mid-mountain
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Crystal Mountain 70†Green Valley
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Paradise: 78â€
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Mt Hood Meadows: 44†mid-mountain
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Olympics: 48â€
In many areas, a layer of buried surface hoar and/or weak sugary facets was buried on December 9th. This layer has been the cause of numerous natural, explosive, and skier triggered avalanches. As this layer gets deeper it gets harder to assess. In short, the scenario is tricky and getting more dangerous by the day.
Higher snowfall totals along the Hwy 542 corridor/Mt Baker area have driven several avalanche cycles during this period. Loading from recent storms has been more incremental to the east and south of the Mt. Baker area, so we have not yet experienced a widespread cycle in other areas.
When will we reach the breaking point? It’s hard to say. What we do know is we have a deep weak layer, reports of very large explosives triggered slides at Mission Ridge and Crystal Mountain, and more storms on the way.
Be patient and continue to stick to lower angle slopes with nothing above you. Â This is a good time to avoid areas where avalanches can start, run, and stop.
We’d like to thank all of you who have sent NWAC your observations. If you are out in the mountains, let us know what you see.
Avalanche Problems
Wind Slabs
Westerly winds Thursday night and Friday will transport new snow near and above treeline, creating shallow fresh wind slabs. Watch for evidence of recent wind transported snow, such as firm surface snow, deep drifts, and wind scoured areas. Human triggered wind slab avalanches are possible on unsupported wind loaded slopes and terrain features 35 degrees and steeper.
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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1