Avalanche Forecast
Issued: Nov 21st, 2020 5:20PM
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,
The winds continue to move snow in the alpine so we have kept the hazard elevated for one more day. Areas with less wind effect will have a lower hazard. Keep an eye on the Nov crust layer, the warmer temps on Sunday and early season hazards.
Summary
Weather Forecast
A slight clearing trend continues on Sunday with a mix of sun and cloud. Upper winds remain in the moderate to strong range switching from the W and SW. Treeline temperatures will be between -10 and -5 C, with a slight inversion forecast in the alpine with temperatures between -8 and -5 C.
Snowpack Summary
Wind slabs present at treeline and above from W-SW winds. At treeline 20-50 cm of storm snow sits over a layer of preserved stellars. The Nov. 5 facet/crust combo is down 50-80 cm and producing variable test results from easy to hard. The Nov crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 50-130 cm.
Avalanche Summary
One new cornice triggered size 1.5-2 avalanche was observed at Bow Summit Saturday. Local ski areas were again able to trigger new wind slabs in the alpine up to size 1.5 and one size 2 cornice, with ski cutting and explosives. On Thursday a skier remote was reported at 2000m near Watermelon Peak size 1.5 on facets to ground, 40cm deep x 80m wide.
Confidence
Intensity of incoming weather systems is uncertain on Sunday
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 Sunday.
- 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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 22nd, 2020 4:00PM
