Bulletin d’avalanche

Stevens Pass

Feb 21 – 22, 2015Northwest Avalanche Center
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Archivé · expiré 12 years ago

Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible

Points saillants

Watch for new wind slab on non-traditional westerly aspects especially as you increase in elevation and reach into the alpine Sunday.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1
  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1

Detailed Forecast

Moderate easterly winds at crest level and in the Passes should lessen Sunday afternoon. Temperatures will warm a few degrees over Saturday, especially in the alpine with high pressure moving into the region.

Watch for new wind slab on non-traditional westerly aspects especially as you increase in elevation and reach into the alpine where there has been more recent snow available for transport. E-NE winds should continue to build new wind slab Saturday night and Sunday morning. There may also be pockets of lingering wind slab on other aspects as well.  

Small loose wet avalanches will be localized to steeper solar slopes near and above treeline and where wind effects are minimal. 

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard. 

Snowpack Discussion

Since the warm and wet start to February, fair weather through mid-February has lead to generally thick surface crusts and further consolidation of the snowpack, as well as further deterioration of the snow cover below treeline.

A few weather disturbances passed through in NW flow aloft the latter half of the week, bringing a welcome few inches of snow near and above treeline; the Paradise weather station recorded 8 inches over 2 days ending Saturday morning. Winds veered to the east or northeast on Saturday, causing some new wind slab formation on non-traditional westerly aspects mainly above treeline.  

On Saturday, NWAC observer reports from the Crystal Mt backcountry described a few inches of new snow bonding well to the old surface and minimal wind transport through mid-day. However, at Winchester Mt in the Mt. Baker area, new wind slab 10 - 40 cm thick was observed by program director Scott Schell above treeline on multiple aspects with new NE wind transport in progress. Little loose wet activity was observed in either location with the cold temperatures and wind.   

The mid and lower snowpack west of the crest snow consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

Régions couvertes