Avalanche Forecast
Issued: Nov 20th, 2020 6:57PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Loose Dry.
Conrad Janzen,
With a slab developing over the Nov 5 crust/facet layer and the continued formation of wind slabs, the snowpack is becoming more complex. Dial back your terrain choices, watch out for rocks, and enjoy the great ski conditions in sheltered areas!
Summary
Weather Forecast
Another 5-10 cm is expected on Friday evening before a slight clearing trend on Saturday. Upper winds remain in the moderate to strong range switching from W to NW. Treeline temperatures will be between -10 and -5 C, with temperatures between -12 to -15 C in the alpine.
Snowpack Summary
20-40 cm new snow over the last few days with Mod-Strong SW winds creating wind slabs at treeline and above. The Nov. 5 facet/crust combo near the base of the snowpack is now down 40-80 cm and producing variable test results. The crust extends up to 2500 m on shady aspects and higher on solar aspects. Total snow depths at treeline are 50-110 cm.
Avalanche Summary
Local ski areas were able to trigger multiple new wind slabs in the alpine up to size 1.5 with ski cutting and explosives. On Thursday a skier remote was reported sz 1.5 on facets to ground (40cm deep x 80 m wide) at 2000m near Watermelon peak. One new cornice triggered size 1.5-2 avalanche was observed at ridge top on Mt Rundle
Confidence
Problems
Wind Slabs
Wind slabs are present at treeline and alpine elevations from recent snow and increased winds. Whumpfing noted on this layer on Thursday and ski hills reporting explosive triggered slabs. Expect these to continue to be reactive to skiers on Saturday.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov.5 crust/ facet layer exists up to 2500m on shady aspects, and higher on solar aspects. Where there is a dense slab overlying this layer, it is starting to become reactive to skier traffic. This will be a layer of concern for a long time.
- Be aware of thin areas that may propogate to deeper instabilites.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Dry
Up to 40cm of new snow in the past few days remains prone to sluffing in steep climbing or skiing terrain like gullies and couloirs. This will be less of a problem in areas that didn't receive as much snow.
- Use caution above cliffs where small avalanches may have severe consequences.
- Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Nov 21st, 2020 4:00PM
