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Avalanche Forecast

Archived

Mar 2nd, 2015–Mar 3rd, 2015

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Stevens Pass.

It is getting to be the time of year when you often need to watch for both winter and spring types of avalanche conditions. It is always good to read the forecast for details.

Detailed Forecast

A period of northeast ridge top winds and east pass winds should be seen in the Cascades this afternoon and tonight.

Then decreasing winds and sunny weather should be seen in the Cascades on Tuesday.

Watch for new shallow wind transported snow on unusual south to west facing slopes on Tuesday. This should be most likely in the Snoqualmie to Mt Rainier area where there was the most recent snow. Older wind slab from February 27th-28th is also most likely to linger on similar slopes in the same area.

The sun will be out and stronger and the days are getting longer so keep an eye on solar slopes for wet snow and signs of loose wet snow on solar slopes on Tuesday.

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

The latest snowfall was February 25-27th when about 8-13 inches fell near and above treeline west of the crest from Snoqualmie to Mt Rainier with less elsewhere along the west slopes.

This was followed by local strong northeast winds in the Cascades February 27-28th.

NWAC pro-observer Jeremy Allyn was at Paradise on February 27th and found 10 inches of new snow bonding well with a favorable density profile. But by mid-day the northeast winds were causing significant snow transport and fresh wind slabs were developing on west aspects. See his video here on the NWAC Instagram account. The Crystal ski patrol also reported a small 1.5 foot skier triggered wind slab on February 28th due to cross loading at 6850 feet. 

NWAC pro-observer Jeff Hambelton was at Mt Baker on February 28th where there was less recent snow and reported no evidence of instability near and below treeline.

Jeremy Allynn was back out at Crystal yesterday and reported many skiers and no avalanches. A report via Turns All Year for Mt St Helens yesterday reported wind slab but no sign of propagation and they did not tempt steeper slopes.

A minor weak weather system yesterday and today did not cause significant precipitation or change in snow conditions.

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.

 

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.