Choose simple terrain and avoid all overhead hazard this long weekend: Fresh wind slabs sit on several critical weak layers. Special Avalanche Warning for the interior ranges. Copy this address to view details: http://bit.ly/2nSOUyX
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
We're looking at cool temperatures and some gusty northerly winds for the next few days. Overnight lows will be near -20 Celsius at tree line. MONDAY: Mostly sunny. Ridge wind gusting moderate from the north / east. Temperature -12. Freezing level valley bottom.TUESDAY: A mix of sun and cloud. Ridge wind strong from the west. Temperature -6. Freezing level 1100m.WEDNESDAY: Flurries (5 -10cm accumulation possible). Ridge wind moderate gusting strong from the north / east. Temperature -7. Freezing level valley bottom.
Avalanche Summary
On Saturday, explosive control produced wind slab results up to size 2 on north facing slopes near 2000m. On Tuesday a snow cat remotely (from a distance) triggered a size 3-3.5 persistent slab avalanche that stepped down from 80-250 cm and ran to ground in the lower start zone on a south aspect at 2100 m. A week ago, the east facing Mt. Corrigan slidepath produced a very large, natural avalanche. The avalanche is estimated to be a size 4.0, and it took out mature timber in the path as it overran the Flathead FSR south of Corbin.
Snowpack Summary
New snow totals from last week vary from 5-20cm above 1700m, thanks to redistribution from north east through to more recent south west winds. Wind slabs up to 20cm thick have formed on down wind (lee) features higher up. Below 1700m, rain on Wednesday formed a thick crust and capped the snow pack. That said, avalanche hazard remains elevated below tree line due to the possibility of large avalanches running full path from higher elevations. For the past month there has been regular avalanche activity on multiple weak layers in the mid and lower snowpack. A layer buried mid January is composed of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and a sun crust on solar aspects and is 60-80 cm deep. Another surface hoar layer from early January is 90-110 cm deep. A widespread weak layer from mid December composed of facets, crusts, and surface hoar is 120-160 cm deep. Finally, a rain crust with sugary facets buried in late November is near the base of the snowpack.The take home message is that several weak layers are still active and deserve a lot of respect. The solution is to stick to conservative terrain while avoiding all overhead hazard.
mgrist,
Avalanche Canada
