Avalanche Forecast
Issued: Apr 18th, 2013 10:20AM
The alpine rating is Wind Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Initially, the approaching frontal system will spread light-moderate precipitation amounts with rising freezing levels. Towards the end of the forecast period a cooling, drying trend will take place before the big warm-up next week.Friday: Overcast with light precipitation amounts. Ridgetop winds will blow moderate from the SW and freezing levels will rise to 2000 m.Saturday: Overcast with moderate precipitation amounts. Ridgetop winds will blow moderate from the NW and freezing levels near 1600 m then falling to valley bottom overnight.Sunday: Mix of sun and cloud with a cooling, drying trend. Freezing levels will rise to 1200 m by the afternoon.
Avalanche Summary
On Wednesday, no new avalanche activity was reported.On Tuesday, a couple of large, older (past 48hrs) slab avalanches size 2-3 were spotted from the flanks of Albert Peak. Crown depths were approximately 50 cm deep and the suspect failure plane may have been the early April surface hoar. In neighboring Glacier National Park, skiers triggered a size 3 slab on a buried crust on an east aspect in the alpine on Monday.
Snowpack Summary
Over the past 2 days, melt-freeze crusts have formed on solar aspects. North aspects remain dry, with new surface hoar development and surface faceting. Forecast snow and wind will likely build new wind slabs and bury an older wind slab problem found at treeline and above. Cornices are very large and remain a concern, threatening slopes below.A weak interface down about 60-120 cm consists of a crust on solar aspects, and surface hoar on high-elevation northerly aspects. Snowpack tests are showing easy-moderate sudden planar compression results in the North Columbia’s. This may be comparable to some areas through-out the South Columbia region. Earlier this week, very large avalanches occurred in this region and in the neighboring Glacier National Park.
Problems
Wind Slabs
Forecast snow and wind will likely build new wind slab problems at treeline and above. Large looming cornices exist on ridgelines and pose a threat to slopes below.
Avoid freshly wind loaded features.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak interface buried down about 60-120 cm has been creating surprisingly large avalanches in neighboring regions. Additional loading by snow and wind may bring the slab above this layer closer to its tipping point.
Be aware of thin areas that may propagate to deeper instabilites.>Dig down to find and test weak layers before committing to a line.>
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 19th, 2013 2:00PM