Avalanche Forecast
Issued: Mar 22nd, 2015 9:26AM
The alpine rating is Persistent Slabs and Storm Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeThe Sea to Sky region is in a lower probability/high consequence avalanche pattern with a snowpack structure that is atypical for this time of year. Conservative terrain selection remains critical.
Summary
Confidence
Fair - Due to the number of field observations on Sunday
Weather Forecast
Scattered convective snowfall (up to 15cm) is expected on Monday as a cold front moves across the region. By late Tuesday a short-lived ridge will bring clearing. On Wednesday a more organized warm and wet frontal system will bring rain to most elevations. Ridgetop winds are expected to be moderate from the southwest with Monday's snowfall, otherwise remaining light. Freezing levels should hover around 1500m on Monday and Tuesday, and then climb to about 2500m with Wednesday's system.
Avalanche Summary
Over the past week, isolated slab avalanches to size 2.5 have occurred on persistent weaknesses buried on March 11th. In a few cases, avalanches failed with light inputs such as remote triggers. Recent heavy snowfall and wind prior to the weekend resulted in widespread storm slab avalanche activity to size 2, but it has also added load to these deeper, more destructive layers. On Sunday, numerous large slab avalanches were observed in the Spearhead Range and on Ipsoot Mtn. The March 11 interface was the suspected culprit in most of these events.
Snowpack Summary
Deep and dense new storm slabs have formed in response to steady wind, snowfall and warm temperatures prior to the weekend. At lower elevations, rain has saturated the snowpack. Cornices may also be fragile. A variably reactive crust/facet persistent weak layer, buried up to 100 cm down, has been the culprit in a few recent destructive avalanches (see avalanche summary). Avalanche problems associated with this layer may linger for a while with the potential for surprisingly large and destructive avalanches in steeper, high elevation terrain. The mid and lower snowpack are generally well-settled and strong.
Problems
Persistent Slabs
On some slopes, persistent weak layers are unlikely to be a problem. On isolated slopes, they may surprise with disastrous consequences. Minimize your risk by avoiding steep, high consequence slopes.
Choose conservative lines and watch for clues of instability.>Pay attention to overhead hazards.>Avoid steep convexities or areas with a thin or variable snowpack.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
New snow and wind forecast for Monday will create new storm slabs in high elevation lee terrain. Due to the convective nature of the system, "power flurries" may occur resulting in higher accumulations than anticipated.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>Use ridges or ribs to avoid pockets of wind loaded snow.>
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 23rd, 2015 2:00PM