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Avalanche Forecast

Archived

Apr 23rd, 2023–Apr 24th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.

Regions

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, Retallack, Valhalla, Whatshan.

Expect continued snow up high, rain down low, and a sloppy mix in the middle. Warm temperatures, rain, and the lack of overnight freeze zaps the strength out of the snow.

Confidence

Low

Avalanche Summary

No new reports of avalanches on Friday or Saturday. Please remember there are few eyes out in the mountains still submitting regular reports.

Expect Storm Slab or Wind Slab avalanches on Monday where more than 20 cm of new snow accumulates. At low elevations avalanche activity is likely to increase as low elevation snow becomes saturated by rain.

Snowpack Summary

Snow continues to accumulate at high elevations on northerly aspects. Generally this recent snow is settling and bonding about as fast as more arrives. Storm slabs may develop in with forecast snow. Windslabs are possible in immediate lee features.

On solar aspects at all elevations, and north aspects at treeline and low elevations, there are many crusts in the upper snowpack. Watch for this snow sitting on a slippery crust. Watch for the snow quickly loosing strength and loose wet avalanches when the sun pokes out.

A layer of surface hoar from March 31 persists down roughly 50 to 100 cm appears to be variable in its distribution. The surface hoar may be sitting above a crust on all but true north-facing slopes. Additional crusts dating from April 7 and April 16 are higher up in the snowpack with similar characteristics and concerns.

The mid-snowpack is strong. However, the November depth hoar remains at the base of the snowpack and remains a concern in rocky, shallow, variable depth snowpack areas at treeline and above.

Weather Summary

Sunday Overnight

Cloudy. Precipitation 5 to 10 mm falling as snow in the alpine, rain down low, and sloppy snow in between . Light southwest winds. Treeline temperatures around zero and freezing level around 2000 m.

Monday

Mostly cloudy. Trace to 5 mm water equivalent of precipitation (rain low, sloppy snow around treeline, snow alpine). Freezing level remaining between 1500 to 2000m. Treeline temperature around zero. Light westerly wind.

Tuesday

Generally clearing up and drying out kind of day. Trace of precipitation. Ridgetop wind light but gusting moderate from the west. Temperatures near zero at treeline with freezing level around 2000 m.

Wednesday

Mix of sunshine with cloud arriving late in the day and precipitation starting up. A trace of preciptiation. Moderate southwest wind, freezing level around 2000 m, treeline temperature around zero.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.