Avalanche Forecast

Cariboos

Date issued

Feb 24, 2018 - 4:27 PM

Valid until

Feb 25, 2018 - 2:00 PM

Prepared by

jmcbride

Expect new snow and strong winds to form storm slabs and grow cornices. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. Avoid wind loaded areas with pillowy or chalky looking snow.

Regular season
Sunday - February 25, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Monday - February 26, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Tuesday - February 27, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Avalanche Problem 1: Storm Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

New snow and strong winds will create storm slabs in many areas in the alpine, as well as open areas at lower elevations. These slabs may be especially deep and touchy in wind-loaded areas on the leeward (down-wind) side of ridges and convex rolls.

Travel and Terrain Advice
  • Watch for whumpfing, hollow sounds, and shooting cracks.
  • Be careful with wind loaded slopes, especially near ridge crests and roll-overs.
  • If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Persistent Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Buried weak layers exist within the snowpack and may be reactive to large triggers such as a cornice or storm slab release. Human triggering may also be possible in shallow or thin, rocky, unsupported terrain.

Travel and Terrain Advice
  • Avoid steep convexities or areas with a thin or variable snowpack.
  • Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Avalanche Summary

There have been no new reports of avalanches since Wednesday (Feb 21) when a size 2, natural cornice release was reported on a southeast aspect at 1900 m in the northern part of the region.

Prior to that on Tuesday, there was a report of a skier triggered size 1.5 soft, wind slab release (25-50 cm deep) on a northeast-facing open, treeline slope at 1900 m, that failed on the mid-February surface hoar layer.

Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

About 5 to 15 cm of new snow now covers the old snow interface which consists of sugary facets as well as sun crust on solar aspects and surface hoar on shaded, wind-sheltered slopes.

Below the old interface lies another interface, with similar character and distribution that was buried mid-February and is now 25-50 cm below the snow surface. This layer has been reactive in recent snowpack tests and recent avalanches have been reported to have failed on this layer in the past week.

Within the mid and lower snowpack are several persistent weak layers that are slowly beginning to show signs of improving but still remain suspect.

Two surface hoar/ crust layers buried in January are now 100-150 cm below the snow surface. At least one of these layers can be found on all aspects and elevations.

Deeper in the snowpack (150 - 200 cm deep) is a facet/crust/surface hoar layer buried in December that is most prevalent at treeline elevations and below.

Near the base of the snowpack is a crust/facet combo layer buried in late November.

Weather Forecast

TONIGHT: Flurries. Accumulation 5-15 cm. Ridge wind strong to extreme, southwest. Temperature -12. Freezing level valley bottom.

SUNDAY: Mostly cloudy, light flurries. Accumulation 2-5 cm. Ridge wind strong, west. Temperature -10. Freezing level valley bottom.

MONDAY: Cloudy, flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature -6. Freezing level 600 m.

TUESDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southwest. Temperature -5. Freezing level 900 m.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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