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West Slopes South - South of I-90 to Columbia River

Special Avalanche Bulletin i

Issued: Mon, April 23, 2018 at 6:00 PM PST
Expires: Thu, April 26, 2018 at 6:00 PM PST

Special Avalanche Bulletin for Monday April 23rd through Thursday April 26th

Issued: 6:00 PM PST Monday, April 23, 2018
by Robert Hahn

Dangerous avalanche conditions are expected this week in the Cascades and Olympics as a major warm-up creates wet snow avalanche conditions on all aspects and elevations. Safe travel during periods of increased avalanche hazard is always possible. You will need to adjust when, where, and how you travel to reduce risks in the mountains this week.  

Danger Scalei
  • No Rating (Info Avail)
  • Low (1)
  • Moderate (2)
  • Considerable (3)
  • High (4)
  • Extreme (5)

Forecast for Tuesday:

Dangerous avalanche conditions are expected this week in the Cascades and Olympics as a major warm-up creates wet snow avalanche conditions on all aspects and elevations. Freezing levels are expected to climb near or above 10,000 feet for several days, marking the first sustained period of above freezing temperatures seen at higher elevations this season. Clear nights will still allow for weak surface refreezing, but these crusts will break down with successive warm days.

The first two and half weeks of April were exceptionally wet and cool, pushing snow depths to seasonal high points for many areas of the Cascades and Olympics. The snowpack this week will struggle as it transitions from cold winter snow to hot spring temperatures. As it makes this abrupt transition expect quickly changing snow and avalanche conditions. Safe travel during periods of increased avalanche hazard is always possible. You will need to adjust when, where, and how you travel to reduce risks in the mountains this week.  

  • Natural and human triggered loose wet avalanches are expected on all aspects and elevations. Even though these avalanches may begin small, they have the ability to grow large and destructive by entraining additional snow.  

    • Travel earlier in the day when snow surfaces are frozen to reduce your risk of loose wet avalanches.

    • When you see new rollerballs, observe fresh fan-shaped debris, or experience wet surface snow deeper than your ankle, you may be able to trigger loose wet avalanches on similar slopes.

    • Use caution if you travel in areas above cliffs, rocks, or gullies. Even small loose wet avalanches in the wrong terrain have resulted in avalanche fatalities in past springs.

  • We have received reports of isolated but very large wet slab and glide avalanches from many areas in the west slopes of the Cascades over the past week. Most of these avalanches appear to have been triggered by cornice falls or loose wet avalanches.

    • Minimize your time in very large avalanche paths by choosing routes and techniques that reduce your exposure. The exact timing of these events is very difficult to predict.

  • Many cornices have grown large over the winter. This time of year, warm sunny weather causes them to droop and eventually fail. This warm-up will be significant enough to cause this to occur in many areas.

    • Do not linger in areas where cornices are above you.

    • Choose travel routes and techniques that limit your exposure to these potential ticking time bombs.

  • Creeks will open and snow bridges will weaken. Fatalities involving open creek holes or collapsed snow bridges occur nearly every spring.

Avalanche Summary:

No Corresponding Mountain Weather Forecast Available