Boletín de aludes

Stevens Pass

Apr 5 – 6, 2015Northwest Avalanche Center
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Archivado · caducó 11 years ago

Peligro de aludes

Tue
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil

Lo esencial

Due to a fair amount of uncertainty with the weather forecast, a moderate hazard rating will be maintained near and above treeline across the Cascades for new storm snow problems.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1
  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

Detailed Forecast

An upper level weather disturbance should bring generally light to locally moderate new snow Sunday night through the first half of Monday followed by scattered afternoon/evening showers. Due to a fair amount of uncertainty with the weather forecast, a moderate hazard rating will be maintained near and above treeline across the Cascades for new storm snow problems. In areas that receive little new snowfall through Monday afternoon... expect a lower avalanche danger than the regional forecast. 

Shallow storm slabs may develop Monday with new snow bonding poorly to aspects with surface crusts. It's April, so be aware of increased solar input reaching more aspects and affecting the snow surface more quickly than winter-time. Loose wet avalanches involving recent storm snow will be possible as well Monday, especially if there are sunbreaks in the afternoon. 

Small loose dry avalanches are also possible on non-solar aspects at higher elevations. Loose dry avalanches won't be listed as a top avalanche problem, but be aware of fast moving sluffs knocking you off your feet and into unintended terrain traps on steeper slopes. 

Due to the continued cool weather, cornices won't be listed as an avalanche problem either but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.

Snowpack Discussion

Periods of active weather and mountain snowfall have finally graced the PNW since about mid March onward, and led to a few natural avalanche cycles. The largest avalanche cycle during this time period was observed in the Mt Rainier area March 25th and mainly above treeline due to rapid warming following heavy snowfall.

A front moved across the Northwest Tuesday followed by showers and rapid cooling. Storm snow from this system ranged from about 3-10 inches along the west slopes except at Snoqualmie Pass where 15-20 inches fell Tuesday night. A small natural cycle occurred at Alpental likely during heavy loading early Wednesday, but overall the new snow came with little avalanche activity. A front on Friday night brought another 1-4 inches across the west slopes. 

The average freezing levels for April have taken a major dive compared to much of this winter, averaging between 3-4000 ft since April 1st. This has helped feed the backcountry reports from across the Cascades near and above treeline of cool, preserved snow on non-solar aspects with limited wind effects, along with gradual storm snow settlement and generally a good bond to the previous crust.  On solar aspects, sun breaks even during low freezing levels have caused generally small loose wet avalanches. Sun crusts may now be found on solar aspects.  

Snowpack problems west of the crest should remain in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this season. Many areas at the low elevations do not have enough snow to cause an avalanche danger.

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