Avalanche Forecast

Archived

Apr 2nd, 2014–Apr 3rd, 2014

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Watch for new and older wind slab on lee aspects near and above treeline. Wet loose avalanches should be confined to lower elevations. Be prepared if weather and avalanche conditions deteriorate quicker than forecast on Thursday.

Detailed Forecast

Rain and snow at relatively cool snow levels should increase in the afternoon Thursday, potentially causing wet loose concerns below 4000 ft and building generally shallow wind slab on NW thru E aspects near and above treeline.

Beside building new wind slab, older wind slab may locally still be sensitive near and above treeline formed over the weekend. Watch for signs of cracking or firmer wind transported snow and approach open lee slopes with caution.

Remember to watch for cornices if you venture onto ridges and avoid slopes below cornices. Cornice failures are often seen during the transition to spring weather. Cornices have grown large recently and often break back much further than anticipated.

Snowpack Discussion

March ended with a return to winter; a storm cycle that began last week peaked over the weekend and delivered about 2 ft of snow at the Hurricane Ridge NWAC weather station.

Increasing rain and snow, winds and warming temps began the increase in avalanche activity Friday with sensitive wind slab reported in the afternoon. Natural wind slab avalanches likely from Saturday were found at Hurricane by Katy on Sunday with several releases up to size 2, mainly 6-12 inches, but with one slab stepping down 2.5 ft on a north slope. Tests indicated a clean interface at about 20 cm in the storm snow. By later Sunday, additional new snow at slightly colder temperatures was creating additional storm and wind slab concerns, especially with the effects of strong solar input at times.

Little or no new snow has fallen since Sunday with periods of sunshine and temperatures reaching in the low 40's midweek. This should have allowed storm weaknesses to quickly settle and stabilize. While we have been in a stabilizing pattern there still may be pockets of unstable wind slab near and above treeline.

The Park ranger at Hurricane Tuesday morning reported widespread but shallow loose wet slides that released during warming Monday.

Wind slab cracking from ski at Hurricane Ridge, near treeline, Sunday 3/30 by NWAC observer Katy Reid.

Natural wind slab avalanches found at Hurricane on Sunday 3/30 by NWAC observer Katy Reid.

Problems

Wind Slabs

Wind Slab avalanches are the 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.