Avalanche Forecast
Issued: Feb 10th, 2018 4:30PM
The alpine rating is Wind Slabs and Deep Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeChoose simple terrain while avoiding all overhead hazard this 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 only isolated flurries for the next few days. Overnight lows will be near -20 Celsius at tree line. SUNDAY: Flurries possible Saturday overnight through to Sunday afternoon with up to 5cm accumulation of low density snow. Ridge wind moderate gusting strong from the north / east. Temperature -9. Freezing level valley bottom.MONDAY: Mostly sunny. Ridge wind light, northeast. Temperature -12. Freezing level valley bottom.TUESDAY: A mix of sun and cloud. Ridge wind light, west. Temperature -9. Freezing level 1100m.
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. 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.
Problems
Wind Slabs
New snow and strong wind have formed reactive wind slabs particularly in wind exposed areas above 1700 m for the Fernie area, while eastern areas saw deeper snow accumulations at lower elevations as well.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Be cautious as you transition into wind affected terrain.If triggered, the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Large avalanches have been running on deep weak layers. Wind loading, fragile cornices, and smaller avalanches are all possible triggers, as well as thin or rocky snowpack areas where human triggering may also be possible.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be aware of the potential for large, deep avalanches.Extra caution needed around cornices with current conditions.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 11th, 2018 2:00PM