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Avalanche Forecast

Archived

Apr 4th, 2016–Apr 5th, 2016

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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Cool weather early Tuesday should give way to warming and sunshine in the afternoon, increasing loose-wet avalanche potential on steep solar slopes. Areas of shallow wind slab may linger on lee aspects at higher elevations, mainly easterly facing. 

Detailed Forecast

Showers should end by early Tuesday with increasing sun breaks, especially by afternoon Tuesday. Temperatures should remain cool Tuesday, with modest warming due to solar input by afternoon.

The shallow recent snow received Monday, in combination with moderate westerly winds may have built areas of wind slab on lee slopes, mainly easterly facing near and above treeline where extra caution is warranted.  Firm wind transported snow and snowpack cracking can be good signs of wind slab layers. 

Small loose wet avalanches, mainly involving any recent new storm snow from Monday and Monday night will be possible on any steeper solar slopes, especially during prolonged sunbreaks Tuesday afternoon. 

The likelihood of cornice failure will lower Tuesday due to cooler weather. However, cornice releases can be unpredictable during the spring so continue to be aware of the overhead hazard and that cornices can break much further back than expected along ridges.

Snowpack Discussion

Weather and Snowpack

A large upper ridge dominated the weather last week through early Sunday, resulting in warm and dry weather. A spring avalanche cycle occurred in most areas over this stretch, likely peaking midweek in the Olympic range. After a stormy March, the snowpack has undergone significant settlement and multiple melt-freeze cycles over the last week.

A front moved across the Olympics early Monday morning, resulting in a period of mostly light precipitation, cooling and moderate westerly crest level winds. 

The mid and lower snowpack in the Olympics should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

NWAC observer, Matt Schonwald toured extensively in the Hurricane Ridge area Saturday, 4/2 and found a well settled and seasonally deep snowpack with very few avalanche concerns. 

During the warm stretch, 1 large glide avalanche (R3-D3) naturally released on the 20th of June slide path (easterly aspect, near treeline) to the ground. According to NPS rangers, the avalanche likely released on Wednesday or Thursday.  

Only shallow amounts of new snow have been received as of Monday afternoon at Hurricane Ridge, leading to a slight increase in danger, mainly on any exposed lee slopes at higher elevations receiving greater wind deposited snow.

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.