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WA Cascades near and west of crest - north of Stevens Pass

Issued: 7:42 PM Friday, April 18, 2014
by Kenny Kramer

Friday 7:30 pm CORRECTED ZONE DANGER LEVEL FORECAST...

Please note that regularly scheduled mountain weather and avalanche forecasts for the past winter season have ended.  However weather and snow conditions will continue to be monitored at the Northwest Avalanche Center with the information that remains available.  Additional forecasts or special statements will be issued according to the criteria and schedule given here.

Increasing winter like avalanche conditions should be seen in the near and above treeline zone by late Saturday afternoon as a front moves across the region.

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Avalanche Concerns

Wind Slabi

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.

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Storm Slabsi

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

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Loose Weti

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

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Snowpack Analysis:

A warm front spread increasing light precipitation over the region late Wednesday with a cold frontal passage moving through the region late Thursday with showers persisting into early Friday.  As of Friday afternoon, areas above 5000 feet had received about 8-12 inches of snow.  

Daytime warming and slightly rising freezing levels Thursday has pushed snow lines above 5500 feet and closer to 6000 feet.  This wet recent snow and added some shallow additional new wet snow above tree line. Cooling overnight Thursday and early Friday allowed for a good bond to form on the old snow surface while adding some shallow, colder new snow amounts. 

The greatest recent storm snow has been received over the Mt Baker area where reports from Thursday and Friday indicated new storm and wind slab were responsive to ski cuts by ski patrol Friday morning and NWAC observer Jeff Hambleton also reported reactive new storm and wind slab while testing new snow conditions.

Storm slab releases on Mt Herman in the Mt Baker backcountry Thursday, April 17th. photo: Jeff Hambleton  

Recent storm slabs and wind slab should settle quickly given the warming daytime temperatures Friday, however they may be also susceptible to becoming wet and creating a wet snow avalanche danger. 

 

Detailed Forecast for Saturday:

An approaching Pacific front should move to the Washington coast Saturday morning, then spread increasing precipitation over the area Saturday afternoon and evening.  Freezing levels should rise ahead of the front, then lower with the onset of precipitation midday Saturday. 

Increasing snow with strengthening winds Saturday afternoon at lowering snow levels should begin to build new wind and storm slab layers.  Depending upon the how early the significant snow begins and the intensities, most areas should only see a modest rise in danger by afternoon.  However, if heavier snowfall begins earlier in the day Saturday, watch for a more significant increase in danger by Satuday afternoon, especially higher elevations. 

The greatest danger increase is expected on lee slopes near and above treeline on mainly north through east facing lee slopes. Watch for signs of firmer wind transported snow or cracking snow.